2-Pyridone, Dimerisation, Aggregation in solution
(NMR-spectroscopy is a slow method, high resolution IR-spectroscopy in solvent is difficult, the broad absorption in UV-spectroscopy makes it hard to discriminate 3 and more very similar molecules).


2-Pyridone, Dimerisation, Aggregation in solution
Some publications only focus one of the two possible patterns, and neglect the influence of the other. For example, to calculation of the energy difference of the two tautomers in a non-polar solution will lead to a wrong result if a large quantity of the substance is on the side of the dimer in an equilibrium.


2-Pyridone, Dimerisation, Tautomerisation mechanism B
The direct tautomerisation is not energetically favoured, but a dimerisation followed by a double proton transfer and dissociation of the dimer is a self catalytic path from one tautomer to the other. Protic solvents also mediate the proton transfer during the tautomerisation.


2-Pyridone, Synthesis
2-Pyrone can be obtained by a cyclisation reaction, and converted to 2-pyridone via an exchange reaction with ammonia:


2-Pyridone, Synthesis
Pyridine forms an N-oxide with some oxidation agents such as hydrogen peroxide. This pyridine-N-oxide undergoes a rearrangement reaction to 2-pyridone in acetic anhydride:


2-Pyridone, Synthesis
In the Guareschi-Thorpe condensation cyanoacetamide reacts with a 1,3-diketone to a 2-pyridone. The reaction is named after Icilio Guareschi and Jocelyn Field Thorpe.


2-Pyridone, Chemical properties, Catalytic activity
2-Pyridone catalyses a variety of proton-dependent reactions, for example the aminolysis of esters. In some cases, molten 2-pyridone is used as a solvent. 2-Pyridone has a large effect on the reaction from activated esters with amines in nonpolar solvent, which is attributed to its tautomerisation and utility as a ditopic receptor. Current interest focuses on proton transfer from 2-pyridone and its tautomer, using isotope labeling, kinetics and quantum chemical methods to determine the rate determining step in the reaction mechanism.


2-Pyridone, Chemical properties, Coordination chemistry
2-Pyridone and some derivatives serve as ligands in coordination chemistry, usually as a 1,3-bridging ligand akin to carboxylate.


2-Pyridone, Chemical properties, In nature
2-Pyridone is not naturally occurring, but a derivative has been isolated as a cofactor in certain hydrogenases.


2-Pyridone, Environmental behavior
2-Pyridone is rapidly degraded by microorganisms in the soil environment, with a half life less than one week. Organisms capable of growth on 2-pyridone as a sole source of carbon, nitrogen, and energy have been isolated by a number of researchers. The most extensively studied 2-pyridone degrader is the gram positive bacterium Arthrobacter crystallopoietes, a member of the phylum Actinobacteria which includes numerous related organisms that have been shown to degrade pyridine or one or more alkyl-, carboxyl-, or hydroxyl-substituted pyridines.


2-Pyridone, Environmental behavior
2-Pyridone degradation is commonly initiated by mono-oxygenase attack, resulting in a diol, such as 2,5-dihydroxypyridine, which is metabolized via the maleamate pathway. Fission of the ring proceeds via action of 2,5-dihydroxypyridine monooxygenase, which is also involved in metabolism of nicotinic acid via the maleamate pathway. In the case of Arthrobacter crystallopoietes, at least part of the degradative pathway is plasmid-borne. Pyridine diols undergo chemical transformation in solution to form intensely colored pigments.


2-Pyridone, Environmental behavior
Similar pigments have been observed in quinoline degradation, also owing to transformation of metabolites, however the yellow pigments often reported in degradation of many pyridine solvents, such as unsubstituted pyridine or picoline, generally result from overproduction of riboflavin in the presence of these solvents. Generally speaking, degradation of pyridones, dihydroxypyridines, and pyridinecarboxylic acids is commonly mediated by oxygenases, whereas degradation of pyridine solvents often is not, and may in some cases involve an initial reductive step.


2-Pyridone (data page), Analytical data, NMR spectroscopy, 1H-NMR
1H-NMR (400 MHz, CD3OD): /ρ = 8.07 (dd,3J = 2.5 Hz,4J = 1.1 Hz, 1H, C-6), 7.98 (dd,3J = 4.0 Hz,3J = 2.0 Hz, 1H, C-3), 7.23 (dd,3J = 2.5 Hz,3J = 2.0 Hz, 1H, C-5), 7.21 (dd,3J = 4.0 Hz,4J = 1.0 Hz, 1H, C-4).


2-Pyridone (data page), Analytical data, NMR spectroscopy, 13C-NMR
(100.57 MHz, CD3OD): ρ = 155.9 (C-2), 140.8 (C-4), 138.3 (C-6), 125.8 (C-3), 124.4 (C-5)


2-Pyridone (data page), Analytical data, IR spectroscopy
(KBr): ν = 3440 cm−1–1 (br, m), 3119 (m), 3072 (m), 2986 (m), 1682 (s), 1649 (vs), 1609 (vs), 1578 (vs), 1540 (s), 1456 (m), 1433 (m), 1364 (w), 1243 (m), 1156 (m), 1098 (m), 983 (m), 926 (w), 781 (s), 730 (w), 612 (w), 560 (w), 554 (w), 526 (m), 476 (m), 451 (w).


2-Pyridone (data page), Analytical data, Mass spectrometry
EI-MS (70 eV): m/z (%) = 95 (100) [ M+], 67 (35) [ M+ - CO], 51 (4)[C4H3+].


2-Pyridylethylamine
2-Pyridylethylamine is a histamine agonist which is selective for the H1 subtype.


2-Pyrone
2-Pyrone (α-pyrone or pyran-2-one) is an unsaturated cyclic chemical compound with the molecular formula C5H4O2. It is isomeric with 4-pyrone.


2-Pyrone
2-Pyrone is used in organic synthesis as a building block for more complex chemical structures because it may participate in a variety of cycloaddition reactions to form bicyclic lactones. For example, it readily undergoes Diels-Alder reactions with alkynes producing, upon loss of carbon dioxide, substituted benzenes. The Gogte Synthesis (1938) is a method for the alkylation of certain pyrones with acid chlorides.


2-Pyrone, Derivatives
The most common natural products containing a 2-pyrone are the bufanolides and kavalactones. Oxovitisin A, a pyranoanthocyanin found in wine, also contains a 2-pyrone element.


2-Pyrone, Derivatives
6-Amyl-α-pyrone (6PP) is a derivative of 2-pyrone, found in animal foods and heated beef. Due to its good organoleptic properties with coconut aroma, it is used as flavor enhancer in the food industry. Biologically, it is produced by Trichoderma species via solid state fermentation.


2-Pyrone, Derivatives
Derivatives of 2-pyrone play a role as signalling molecules in bacterial communication, similar to quorum sensing. Cells with LuxR-type receptors, but lacking its homolog LuxI (and thus unable to produce N-acylhomoserine lactone QS signaling molecules) are known as LuxR "solos", to which pyrones bind as ligands facilitating cell-cell communication.


2-Pyrrolidone
2-Pyrrolidone, also known as 2-pyrrolidinone or butyrolactam, is an organic compound consisting of a 5-membered lactam, making it the simplest γ-lactam. It is a colorless liquid that is miscible with water and most common organic solvents.


2-Pyrrolidone
2-Pyrrolidone itself and various derivatives made from it have a variety of industrial uses.


2-Pyrrolidone, Production
2-Pyrrolidone is produced industrially almost exclusively by treating aqueous gamma-butyrolactone with ammonia at a temperature of 250–290 °C and pressures ranging from 0.4–1.4 MPa over solid magnesium silicate catalysts.


2-Pyrrolidone, Production
The reaction is carried out in a tubular reactor which is packed with the solid catalyst. The latter is arranged as a fixed bed and the reaction is carried out in the vapor phase. Product yields of 75–85% are reached. After subsequent distillation and purification, the desired 2-pyrrolidone is obtained with a purity of 99.5%.


2-Pyrrolidone, Production
Alternative routes include the catalytic or electrochemical reduction of succinimide, the carbonylation of allylamine, the hydrogenation of succinonitrile under hydrolytic conditions and the reaction of maleic or succinic anhydride in aqueous ammonia with Pd–Ru-catalysts.


2-Pyrrolidone, Production
In 2010, the worldwide demand for 2-pyrrolidone was estimated to be 32.000 t. Important manufacturers of 2-pyrrolidone are BASF and ISP (International Speciality Products, now Ashland Inc.).


2-Pyrrolidone, Uses
A variety of pharmaceutical drugs are 2-pyrrolidone derivatives, including cotinine, doxapram, povidone, and ethosuximide, and the racetams.


2-Pyrrolidone, Uses
The chemical is an intermediate in the production of the polyvinylpyrrolidone precursor vinylpyrrolidone and the solvent N-methylpyrrolidone (NMP).


2-Quinolone
2-Quinolone is an organic compound related structurally to quinoline. It is the majority tautomer in equilibrium with 2-quinolinol. The compound can be classified as a cyclic amide, and as such is used as an isostere for peptides and other pharmaceutically-inspired targets. The isomer 4-quinolone is the parent of a large class of quinolone antibiotics.


2-Succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase
In enzymology, SEPHCHC synthase  (EC EC ), encoded by menD gene in E. coli, is an enzyme that catalyzes the second step of menaquinone (vitamin K2) biosynthesis. The two substrates of this enzyme are 2-oxoglutarate and isochorismate. The products of this enzyme are 5-enolpyruvoyl-6-hydroxy-2-succinyl-cyclohex-3-ene-1-carboxylate and CO2. It belongs to the transferase family.


2-Succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase, Classification
This enzyme belongs to a family of enzymes that transfer aldehyde or ketonic groups. To be specific, this enzyme belongs to the transketolase and transaldolase families. Common names for the enzyme are:


2-Succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase, Reaction
In the biosynthesis of vitamin K, SEPHCHC is involved in the second step of the pathway. The type of reaction is decarboxylating, and to have maximum activity, this enzymes uses the cofactor Mg2+, a magnesium ion. In previous years, it was thought that this reaction led to SHCHC, the product MenH. After further research, we now know that this reaction is a new step in the pathway. The actual product of this enzyme can lose a pyruvate spontaneously.


2-Succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase, Structure
The structures reveal a stable dimer-of-dimers association in agreement with gel filtration and analytical studies confirm the classification of MenD in the pyruvate oxidase family. The active site is highly basic with a hydrophobic patch. These features match with the chemical properties of the substrates.


2-Succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase, Homologues
There are many similar structures MenD. Though it is commonly found in E. Coli, but can be found in other organisms as well. Bacillus subtilis and Mycobacterium tuberculosis are two homologues. All of the organisms share something in common, being that catalyze decarboxylation reactions.


2-Tetralone
2-Tetralone is an organic chemical compound with the molecular formula C10H10O. This colourless oil is an intermediate in organic synthesis. It is a ketone derivative of tetralin, a hydrogenated derivative of naphthalene. A related compound is 1-tetralone.


2-Tetralone, Applications
2-Tetralone is an intermediate in the synthesis of a variety of pharmaceutical drugs including L-687,384, nepinalone, napamezole, spirodone, and trioxifene.


2-Thiouracil
2-Thiouracil is a specific molecule consisting of a sulfated uracil.


2-Thiouracil, Medical use
The substance is a historically relevant anti-thyroid preparation. Astwood E.B. used it in 1943 as therapy of Graves' disease for the first time. It remains in use.


2-Thiouracil, Medical use
Thiouracil inhibits thyroid activity by blocking the enzyme thyroid peroxidase. Its use in recent times has been replaced by advent of more potent and safer antithyroid drugs. It occurs in seeds of Brassica and Crucifera species. Thiouracil has been used as antithyroid, coronary vasodilator, and in congestive heart failure although its use has been largely supplanted by other drugs.


2-Undecanone
2-Undecanone, also known as methyl nonyl ketone and IBI-246, is the organic compound with the formula CH3C(O)C9H19. It a colorless oil. It is usually produced synthetically, but it can also be extracted from various plant sources, including from essential oil of rue. It is found naturally in bananas, cloves, ginger, guava, strawberries, wild-grown tomatoes, and the perennial leaf vegetable Houttuynia cordata.


2-Undecanone, Uses
Because of its strong odor it is primarily used as an insect repellent or animal repellent. Typically, 1–2% concentrations of 2-undecanone are found in dog and cat repellents in the form of a liquid, aerosol spray, or gel. 2-Undecanone is also used in the perfumery and flavoring industries.


2-Undecanone, Uses
It has been investigated as a mosquito repellant, like DEET.


2-Undecanone, Chemical properties
2-Undecanone is a ketone that  is soluble in organic solvents but insoluble in water. Like most methyl ketones, 2-undecanone undergoes a haloform reaction when in the presence of a basic solution of hypochlorite. For example, the reaction between 2-undecanone and sodium hypochlorite yields sodium decanoate, chloroform, and sodium hydroxide.


2-VLG-V (ML-KNIL)
2e Afdeling, Vliegtuiggroep V (2nd Squadron, Airgroup 5) or short 2-VLG-V was a squadron of the Royal Netherlands East Indies Army Air Force from the 1st of July 1941 to the 8th of March 1942.


2-VLG-V (ML-KNIL), Establishment
Before the war in Europe, the Royal Netherlands East Indies Army Air Force (ML-KNIL) consisted of old planes and a handful of pilots. The Netherlands already had plans to reorganize the ML-KNIL and when Nazi-Germany overcame the Netherlands, it was given the first priority. On 1 June 1941, the 'Tweede Afdeling' (second division) was formed on Semplak. This would be a fighter division, consisting mainly of Curtiss-Wright Model 21 Interceptors and Brewster B-339C/D Buffalos. The first squadron (1-VLG-V) would use the interceptors, but because those were not delivered yet, 1-VLG-V was used as a test-squadron for the newly arrived Buffalos.


2-VLG-V (ML-KNIL), Establishment
When at the end of June the first interceptors arrived, a second squadron within this division was created on 1 July 1941, 2-VLG-V. The squadron leader was Capt. Jacob Pieter van Helsdingen. The plan was that 2-VLG-V, consisting of 12 pilots, would get 12 ready to use Buffalos, and 12 spare Buffalos. However, at the end of the war, only 17 Buffalos would have been used by 2-VLG-V.


2-VLG-V (ML-KNIL), Battles, Battle of Malaya
On 25 December 1941, 12 Buffalos together with 12 pilots of 2-VLG-V were stationed at Kallang, for the defence of Singapore. These Buffalos were fitted with a bomb-rack, so that they could be used for dive-bombing. The Buffalos of the ML-KNIL didn't have bulletproof glass (it was ordered but Brewster couldn't deliver it). However the Buffalos from 2-VLG-V that helped defend Singapore were fitted with bulletproof glass from damaged British buffalos. During several actions above and near Singapore, 2-VLG-V managed to sink a Japanese destroyer, and shot down four Japanese aircraft. During the actions above Singapore, one pilot from 2-VLG-V was killed. The pilots and Buffalos that flew above Singapore were:


2-VLG-V (ML-KNIL), Battles, Battle of Java
On 18 January 1942 the Buffalos that fought above Singapore were called back to help defend Java, prior to the Battle of Singapore. Because of several crashes and losses the squadron had to be reorganized. A couple of pilots from other squadrons were transferred to 2-VLG-V, and all the Buffalos were re-arranged. So did Deibel, who was shot down above Singapore with B-3100, and crashed with B-398 received the former aircraft of squadron leader Van Helsdingen. While Van Helsdingen received a new aircraft. Below is a short list of the re-arrangement as far as known:


2-VLG-V (ML-KNIL), Battles, Battle of Java
On 19 January, 8 Buffalos from 2-VLG-V intercepted a formation of about 35 Japanese bombers with an escort of about 20 Zeros. The Buffalo pilots destroyed 11 Japanese aircraft. Vdg. J.P. Kuijpers, Sgt. N.G. de Groot, Vdg. J. Scheffer, and Sgt. P.C. 't Hart were all shot down, Kuijper and de Groot were killed.


2-VLG-V (ML-KNIL), Battles, Battle of Balikpapan
In the afternoon of January 23, all Buffalos from 2-VLG-V together with several Buffalos from 3-VLG-V and nine Martin Model 166 bombers attacked the Japanese fleet in the Makassar Strait. One pilot (Rothkrans) was shot down and killed during this action. The Buffalos were all fitted with bomb-racks and two 110 lbs bombs. The Buffalos from 2-VLG-V were given 8 positive hits on several ships. One ship, the Nana Maru was sunk.


2-VLG-V (ML-KNIL), Battles, Battle of Balikpapan
On Sunday, March 1, at 5:30 nine Brewster Buffalos set out for Eretanwetan, one flight of four aircraft of 2-VLG-V led by Captain van Helsdingen, the other flight - from 1-VLG-V - led by Captain van Rest. Three Glenn Martin Bombers of 3-VLG-III also took part in this action. One Japanese transport was claimed sunk, but the Glenn Martins also lost one of their number; Lieutenant B. Groenendijk and his crew were killed in action. One of the Brewsters belly-landed at Andir airfield, the pilot being unable to lower his undercarriage.


2-VLG-V (ML-KNIL), Last Flight
On 7 March 1942, van Helsdingen was given the order to give air support to Royal Dutch East Indies Army forces fighting in Lembang. Despite the Japanese having an almost complete air superiority over Java, he nevertheless chose to take off from Andir airfield. He asked all available pilots who wanted to volunteer. All pilots volunteered and van Helsdingen picked four pilots who then jumped in the four last remaining Buffalos. Just before take-off, van Helsdingen was informed by another pilot that one of the chosen pilots was married.


2-VLG-V (ML-KNIL), Last Flight
Despite being married himself van Helsdingen took the place of the married pilot, and the four Buffalos took off. The three other pilots were: 1st Lieutenant August Deibel, Sergeant Gerard Bruggink and Officer Cadet Jan Scheffer. After only travelling 200 kilometers they ran into three Mitsubishi A6Ms. Deibel's plane was hit in the oil tank and he had to break off from combat. His wingman, Scheffer, escorted him back to Andir airfield, where Deibel crash landed his aircraft without injury. The other two remained above Lembang, but were now dogfighting six Mitsubishi A6Ms.


2-VLG-V (ML-KNIL), Last Flight
Van Helsdingen was soon shot down, but Bruggink managed to escape into the clouds before returning to Andir airfield. The Dutch forces in Lembang surrendered the next day. Bruggink and Deibel were awarded the Military William Order, the highest award available from the Netherlands, while van Helsdingen and Scheffer (who died a prisoner of war) were posthumously awarded the honour on 14 July 1948.


2-VLG-V (ML-KNIL), Decorations
Even though the squadron was short-lived, it has been one of the most highly decorated squadrons of the Dutch East Indies.


2-VLG-V (ML-KNIL), Decorations
1 x Knight 3rd Class of the Military Order of William


2-VLG-V (ML-KNIL), Decorations
4 x Knight 4th Class of the Military Order of William


2-Vinyl-4,6-diamino-1,3,5-triazine
2-Vinyl-4,6-diamino-1,3,5-triazine is an organic compound with the formula (H2NC)2N3CCH=CH2. The molecule consists of a vinyl group (-CH=CH2) attached to a 2,4-diaminotriazine. A colorless solid, it is a monomeric precursor to polymers with hydrogen-bonding substituents.


2-Vinylpyridine
2-Vinylpyridine is an organic compound with the formula CH2CHC5H4N. It is a derivative of pyridine with a vinyl group in the 2-position, next to the nitrogen. It is a colorless liquid, although samples are often brown. It is used industrially  as a precursor to specialty polymers and as an intermediate in the chemical, pharmaceutical, dye, and photo industries. Vinylpyridine is sensitive to polymerization. It may be stabilized with a free radical inhibitor such as tert-butylcatechol. Owing to its tendency to polymerize, samples are typically refrigerated.


2-Vinylpyridine, Synthesis
It was first synthesized in 1887. A contemporary preparation entails condensation of 2-methylpyridine with formaldehyde, followed by dehydration of the intermediate alcohol. The reaction is carried out between 150–200 °C in an autoclave. The conversion is kept relatively low. After removal of unreacted 2-methylpyridine by distillation, concentrated aqueous sodium hydroxide is added to the residue and the resultant mixture is distilled under reduced pressure. During distillation, the dehydration of 2-(2-pyridyl)ethanol occurs to give 2-vinylpyridine, which can be purified further by fractional distillation under reduced pressure in the presence of an inhibitor such as 4-tert-butylcatechol.


2-Vinylpyridine, Synthesis
An alternative synthesis involves the reaction of acrylonitrile and acetylene below 130–140  ̊C in the presence of organocobalt compounds as a catalyst. Acrylonitrile is the solvent for the reaction.


2-Vinylpyridine, Uses, Polymeric derivatives
2-Vinylpyridine is readily polymerized or copolymerized with styrene, butadiene, isobutylene, methyl methacrylate, and other compounds in the presence of radical, cationic, or anionic initiators. The homopolymer is soluble in organic solvents such as methanol and acetone, whereas cross-linked copolymers are insoluble in organic solvents.


2-Vinylpyridine, Uses, Polymeric derivatives
An important application of 2-vinylpyridine involves the production of a latex terpolymer of 2-vinylpyridine, styrene, and butadiene, for use as a tire-cord binder. The tire cord is treated first with a resorcinol-formaldehyde polymer and then with a terpolymer made from 15% 2-vinylpyridine, styrene, and butadiene. This treatment gives the close bonding of tire cord to rubber.


2-Vinylpyridine, Uses, Polymeric derivatives
2-Vinylpyridine is a co-monomer for acrylic fibers. Between 1–5% of copolymerized 2-vinylpyridine provide the reactive sites for dyes.


2-Vinylpyridine, Uses, Organic synthesis
Due to the electron-withdrawing effect of the ring nitrogen atom, 2-vinylpyridine adds nucleophiles such as methoxide, cyanide, hydrogen sulfide at the vinylic site to give addition products. The addition product of methanol to 2-vinylpyridine, 2-(2-methoxyethyl)pyridine is a veterinary anthelmintic.


2-Vinylpyridine, Uses, Organic synthesis
Treating 2-vinylpyridine with 4-pyridinecarbonitrile and hydrogen chloride gives 1-[2-(2-pyridyl)ethyl]-4-cyanopyridinium chloride, which then can be used to prepare dimethylaminopyridine (DMAP), a widely used base catalyst.


2-Vinylpyridine, Uses, Organic synthesis
2-Vinylpyridine is used in the production of Axitinib, a pharmaceutical.


2-Way (Lil' Romeo Song)
"2-Way" is the first single from Lil' Romeo's second studio album Game Time. The track features additional vocals from his dad Master P and Silkk The Shocker. It is an almost-complete cover of "It Takes Two" by Rob Base and DJ E-Z Rock, with slight lyrical alterations to the original (i.e. references in Base's own lyrics to himself) and additional samples. The song was played at the ending credits of Hey Arnold! : The Movie. It also appeared in the movie Kangaroo Jack.


2-Way (Lil' Romeo Song), Music video
A music video for the track was filmed in April 2002. Two versions of the video were made. The first is when Romeo is performing the song in a basketball stadium & a basketball outfit. The music video also involves the North Miami Beach High School Marching Chargers. The second version includes a basketball game and scenes from Hey Arnold! : The Movie.


2-XL
2-XL (2-XL Robot, 2XL Robot, 2-XL Toy) is an educational toy robot that was marketed from 1978–1981 by the Mego Corporation, and from 1992–1995 by Tiger Electronics. 2-XL was the first "smart-toy" in that it exhibited rudimentary intelligence, memory, gameplay, and responsiveness. 2-XL was infused with a "personality" that kept kids focused and challenged as they interacted with the verbal robot. Learning was enhanced via the use of jokes and funny sayings as verbal reinforcements for performance. 2-XL was heralded as an important step in the development of toys, particularly educational ones. 2-XL won many awards, and Playthings, a toy industry magazine, placed 2-XL on its 75th anniversary cover as one of the industry's top-ten toys of all time. The 2-XL name is a pun of the phrase "To Excel".


2-XL, History and development
The toy was invented and licensed for manufacture by Michael J. Freeman, inventor, Ph.D. and was patented. 2-XL exhibited rudimentary intelligence, memory, gameplay, and responsiveness. Dubbed the "Toy with a Personality," 2-XL could respond verbally to the user depending upon which "input or answer" buttons were chosen. 2-XL during its run was one of the most popular toys in terms of market revenue and was dubbed the Talking Robot with a mind of its own.


2-XL, History and development
The toy was voiced by Freeman,using a synthesizer to make his voice a high-pitched robot-like sound; it was through this process that Freeman developed 2-XL's personality. 2-XL was first introduced in 1978 by the Mego Corporation, a publicly traded US-based toy company in New York City and it subsequently  became a success. The toy was sold in different countries and the tapes were translated into seven foreign languages. Games were also developed for the toy.


2-XL, History and development
Mego, otherwise known for its production of dolls and classic action figures in the 1970s, was seen as an innovator combining toys and education. The toy's name literally meant "To Excel". The toy was voice capable, was able to tell stories, and sing using its special 8-track tapes. The toy's tapes asked multiple-choice questions (MCQs) that were answered by pushing a YES or NO button that changed the tracking of the tape. It was a crude but reportedly innovative use of the technology that was present in that era.


2-XL, History and development
In addition to its general popularity, 2-XL was unprecedented in terms of market revenue. "The 2XL was hot, in demand, and everyone wanted one." "It was a great way to make learning cool and fun." Playthings magazine, in its cover story of September 1978, considered the 2-XL robot as one of the most important toys ever developed, and included it in a class of "toys with impact" along with the Teddy Bear, Barbie Doll, Raggedy Ann, Mickey Mouse among others. The robot was a popular educational toy whose success anticipated the dominant influence of technology in education today. Dubbed the "Toy with a Personality," 2-XL could respond verbally to the user depending upon which "input or answer" buttons were chosen. Part of the reason for this is the connection the toy made between education and fun. "2-XL was a glorious display of plastic robotics."


2-XL, History and development
2-XL was interactive playing various tracks from a magnetic audio tape depending on the user's actions. 2-XL's personality was very popular and kids loved the back-and-forth banter. For example, If a child got an answer wrong 2-XL might utter something like: "perhaps your brain went on strike! You are Wrong." Or, "Nice try but (whispering) you are wrong, but go ahead, I will be a nice little toy robot and give you a second chance now." "Even though you needed two chances you finally got the answer right, elephant is the correct answer"'.


2-XL, History and development
"But do not get too excited, you have now earned yourself a more difficult question. Hold on to your hat, here it comes" If the child was right, 2-XL might say: "Although I have the looks you have the brains. You must be a genius. Good work." Or, "it is amazing that big brain of yours fits into the head of a child. Nice answer, football is correct."


2-XL, History and development
In 1981, the toy's popularity waned, and it was later discontinued. In 1992, 2-XL was re-introduced by Tiger Electronics, a toy company based in Vernon Hills, Illinois. The toy was changed into a more modern design, and new programmed toy cartridges were also introduced. The voice for this version was done by Freeman as well, and all programs were translated into many different languages.


2-XL, Versions, Mego Corporation version
The original version, created by Mego Corporation, was made of brown plastic with white plastic found on the anterior face of the robot. It had two red light bulbs for the eyes. These bulbs also flashed at moments while 8-track cartridge tape programs played. It had four red buttons on its stomach with designated options for answers to questions asked by the toy, such as "Question," "A or Yes Or True," "B or More Info," and "C or No or False. A knob is also found on the lower right portion of the toy which controlled its volume and power. The "mouth" was reused detail molding taken from the Micronauts Battle Cruiser. At the bottom was a large slot for the 8-track cartridge tapes.


2-XL, Versions, Mego Corporation version
This particular version was essentially a regular 8-track tape player, but by utilizing unique, clever, and patented mathematical decision tree programming methods, over 20 interactive modes of operation were achieved. It seemed to most people like a computer which had enough information and interactive questions to entertain and educate a child (or adult) up to two hours. Subjects included sports quiz, Guinness Book of World Records, the metric system, general information and jokes.


2-XL, Versions, Mego Corporation version
The mold and look got a minor change in 1980. The eye lights became red and responded to the voice. The flashing lights also became brighter, and the speaker in the back of the unit was changed from a hexagon shape to a more traditional round. The plastic was glossier looking.


2-XL, Versions, Tiger Electronics version
Tiger Electronics re-introduced 2-XL in 1992. Instead of using 8-track cartridge tapes, this version used cassette tapes that were twice the length of the tapes in the previous version and had a better sound quality. Freeman again recorded the 2-XL voice for the cassette tapes in a professional sound studio. In addition to eyes that would light up the toy now sported a circle for a mouth that could light up as the machine talked. The toy could now run on batteries and had a headphone jack.


2-XL, Versions, Tiger Electronics version
Instead of the buttons simply switching tracks on the 8-track tape as in the old version, the cassette version took advantage of the fact that a cassette has a total of four tracks - one for the left and right channel on each side. The tape head in the player could play any of the four parallel tracks, based on which button was pressed.


2-XL, Versions, Tiger Electronics version
Playing a 2-XL tape in a standard tape player would result in different audio on the left and right channels, and if the reverse side was played, one would hear the other two tracks played in reverse. Using all four tracks simultaneously was unique to 2-XL and provided the basis for the interactive give and take.


2-XL, Versions, Tiger Electronics version
As with the previous version, this version could play any standard tape of similar tape, but the user needed to first push the "Question" button (or the "2/A/No" button would work as well, playing the correct channel). Pressing three or four buttons would play one of the channels on the reverse side of the tape backwards.


2-XL, Versions, Tiger Electronics version
Newly released tapes were branded with comic book and cartoon characters, including Spider-Man, Star Trek: The Next Generation, Mighty Morphin Power Rangers, X-Men and Batman. 2-XL games would allow the user to go on an adventure with various superheroes, deciding their fate by pushing one of the buttons. The second version was on the market from 1992 through 1996, and about 45 tapes were released in total. The toy was sold internationally, including in Japan, Germany, Hungary, Italy, France, UK, Ireland, Canada, Brazil (where it was distributed by Nintendo's official local licenser Playtronic) and others. The tapes were translated into many foreign languages, but were not recorded by Freeman.


2-XL, Television series spinoff
The toy's success was also the basis for a game show called Pick Your Brain produced by Marc Summers Productions and Summit Media Group. The 2-XL robot in the show served as the assistant of Marc Summers. 2-XL was also a spokesrobot for basketball player Michael Jordan and his charitable foundation in 1992 and 1993 and appeared in a number of PSA (public service announcements) with Jordan.


2-XL, Tapes, List of 2-XL tapes manufactured by Mego Corporation between 1978 and 1981
General Information was included with each toy robot. The remainder programs were each sold separately:


2-XL, Tapes, List of 2-XL tapes manufactured by Tiger Electronics between 1992 and 1995
The World of 2-XL was sold with each toy robot. The remainder programs were each sold separately. For foreign sales, the Freeman voiced 2-XL English language tapes were translated into foreign languages performed by a professional that spoke the designated language.


2-XL, Tapes, Trilex
One of the last tapes released for the Mego Corporation version of 2XL was "Trilex", a complete board game designed to be played against 2XL. The tape came with a board which fitted over the front of the 2XL unit itself, with the board in front of the tape slot. The game board consisted of an inverted pyramid shape, 4 squares wide at the top to 1 square at the bottom, with each row colored in a different color (Blue, Yellow, Green, and Tan), and 4 slots through which pieces (which 2XL called "checkers") could be dropped into the pyramid.


2-XL, Tapes, Trilex
The slots aligned with 2XL's 4 buttons, with the intention that dropping the checker would also press the appropriate track button on 2XL. The objective of the game was to create either a line or a triangle of three checkers of a selected color. The game and tape design are interesting because they enabled the 4-track tape player to provide a passable simulation of a game-playing AI.


2-XL, Merchandising
A number of secondary products were licensed under the 2-XL (2XL) name including: laptop computer bags, earphones, lunch boxes and more.


2-XL, Awards
During its time, both iterations of 2-XL won hundreds of awards, including FamilyFun magazine's award for best toy of 1992, and Right Start Magazine's honor as Europe's best toy in the 3-5 year-old category for 1993. For the 75th anniversary issue of Playthings magazine, 2-XL was featured on the cover and named one of the top ten toys of all time. The Tiger 2-XL was also the winner of the 1992 Walt Disney Company Best Learning Toy for 1992.


2-Z (album)
2-Z is an album by American jazz pianist Matthew Shipp with AACM saxophonist Roscoe Mitchell, which was recorded in 1995 and released on the 2.13.61 label. Shipp played previously with Mitchell's Note Factory on the album This Dance Is for Steve McCall, but 2-Z represents their first collaboration with Shipp as a leader.


2-Z (album), Reception
In his review for AllMusic, Chris Kelsey states "The men speak the same language —albeit with slightly different accents— and they communicate quite well. A nice record." The Penguin Guide to Jazz says about the album that "is a meeting of generations, and Shipp sounds respectful and happy to take second place for much of it, constantly searching for some normative path that might hint at a tonal centre".


2-acetolactate mutase
In enzymology, a 2-acetolactate mutase (EC ) is an enzyme that catalyzes the chemical reaction


2-acetolactate mutase
Hence, this enzyme has one substrate, 2-acetolactate, and one product, 3-hydroxy-3-methyl-2-oxobutanoate.


2-acetolactate mutase
This enzyme belongs to the family of isomerases, specifically those intramolecular transferases transferring other groups. The systematic name of this enzyme class is 2-acetolactate methylmutase. Other names in common use include acetolactate mutase, and acetohydroxy acid isomerase. This enzyme participates in valine, leucine and isoleucine biosynthesis. It employs one cofactor, ascorbate.


2-acylglycerol O-acyltransferase
In enzymology, a 2-acylglycerol O-acyltransferase (EC ) is an enzyme that catalyzes the chemical reaction


2-acylglycerol O-acyltransferase
Thus, the two substrates of this enzyme are acyl-CoA and 2-acylglycerol, whereas its two products are CoA and diacylglycerol.


2-acylglycerol O-acyltransferase
This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acyl-CoA:2-acylglycerol O-acyltransferase. Other names in common use include acylglycerol palmitoyltransferase, monoglyceride acyltransferase, acyl coenzyme A-monoglyceride acyltransferase, and monoacylglycerol acyltransferase. This enzyme participates in glycerolipid metabolism.


2-acylglycerol-3-phosphate O-acyltransferase
In enzymology, a 2-acylglycerol-3-phosphate O-acyltransferase (EC ) is an enzyme that catalyzes the chemical reaction


2-acylglycerol-3-phosphate O-acyltransferase
Thus, the two substrates of this enzyme are acyl-CoA and 2-acyl-sn-glycerol 3-phosphate, whereas its two products are CoA and 1,2-diacyl-sn-glycerol 3-phosphate.


2-acylglycerol-3-phosphate O-acyltransferase
This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acyl-CoA:2-acyl-sn-glycerol 3-phosphate O-acyltransferase. This enzyme is also called 2-acylglycerophosphate acyltransferase. This enzyme participates in glycerophospholipid metabolism.


2-acylglycerophosphocholine O-acyltransferase
In enzymology, a 2-acylglycerophosphocholine O-acyltransferase (EC ) is an enzyme that catalyzes the chemical reaction


2-acylglycerophosphocholine O-acyltransferase
Thus, the two substrates of this enzyme are acyl-CoA and 2-acyl-sn-glycero-3-phosphocholine, whereas its two products are CoA and phosphatidylcholine.


2-acylglycerophosphocholine O-acyltransferase
This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acyl-CoA:2-acyl-sn-glycero-3-phosphocholine O-acyltransferase. Other names in common use include 2-acylglycerol-3-phosphorylcholine acyltransferase, and 2-acylglycerophosphocholine acyltransferase. This enzyme participates in glycerophospholipid metabolism.


2-alkenal reductase
In enzymology, a 2-alkenal reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-alkenal reductase
The 3 substrates of this enzyme are n-alkanal, NAD+, and NADP+, whereas its 4 products are alk-2-enal, NADH, NADPH, and H+.


2-alkenal reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is n-alkanal:NAD(P)+ 2-oxidoreductase. Other names in common use include NAD(P)H-dependent alkenal/one oxidoreductase, and NADPH:2-alkenal alpha,beta-hydrogenase.


2-alkenal reductase, Structural studies
As of late 2007, three structures have been solved for this class of enzymes, with PDB accession codes , , and .


2-alkyn-1-ol dehydrogenase
In enzymology, a 2-alkyn-1-ol dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction below:


2-alkyn-1-ol dehydrogenase
The two substrates of this enzyme are 2-butyne-1,4-diol and NAD+, whereas its 3 products are 4-hydroxy-2-butynal, NADH, and H+.


2-alkyn-1-ol dehydrogenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 2-butyne-1,4-diol:NAD+ 1-oxidoreductase.


2-amino-3,7-dideoxy-D-threo-hept-6-ulosonate synthase
2-amino-3,7-dideoxy-D-threo-hept-6-ulosonate synthase (EC , ADH synthase, ADHS, MJ0400 (gene)) is an enzyme with systematic name L-aspartate 4-semialdehyde:1-deoxy-D-threo-hexo-2,5-diulose 6-phosphate methylglyoxaltransferase. This enzyme catalyses the following chemical reaction


2-amino-3,7-dideoxy-D-threo-hept-6-ulosonate synthase
The enzyme plays a key role in an alternative pathway of the biosynthesis of 3-dehydroquinate.


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase
In enzymology, a 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase (EC ) is an enzyme that catalyzes the chemical reaction


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase
Thus, the two substrates of this enzyme are ATP and 2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine, whereas its two products are AMP and (2-amino-4-hydroxy-7,8-dihydropteridin-6-yl)methyl diphosphate.


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase
This enzyme belongs to the family of transferases, specifically those transferring two phosphorus-containing groups (diphosphotransferases). The systematic name of this enzyme class is ATP:2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine 6'-diphosphotransferase. Other names in common use include 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine pyrophosphokinase, H2-pteridine-CH2OH pyrophosphokinase, 7,8-dihydroxymethylpterin-pyrophosphokinase, HPPK, 7,8-dihydro-6-hydroxymethylpterin pyrophosphokinase, and hydroxymethyldihydropteridine pyrophosphokinase. This enzyme participates in folate biosynthesis.


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase
This enzyme catalyses the first step in a three-step pathway leading to 7,8 dihydrofolate. Bacterial HPPK (gene folK or sulD) is a protein of 160 to 270 amino acids. In the lower eukaryote Pneumocystis carinii, HPPK is the central domain of a multifunctional folate synthesis enzyme (gene fas).


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase, Structural studies
As of late 2007, 23 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , , , , , , , , , , , , , and .


2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase, Further reading
This EC 2.7 enzyme-related article is a stub. You can help Wikipedia by .


2-amino-5-formylamino-6-ribosylaminopyrimidin-4(3H)-one 5'-monophosphate deformylase
2-amino-5-formylamino-6-ribosylaminopyrimidin-4(3H)-one 5'-monophosphate deformylase (EC , ArfB) is an enzyme with systematic name 2-amino-5-formylamino-6-(5-phospho-D-ribosylamino)pyrimidin-4(3H)-one amidohydrolase. This enzyme catalyses the following chemical reaction


2-amino-5-formylamino-6-ribosylaminopyrimidin-4(3H)-one 5'-monophosphate deformylase
The enzyme catalyses the second step in archaeal riboflavin and 7,8-didemethyl-8-hydroxy-5-deazariboflavin biosynthesis.


2-aminoadipate transaminase
In enzymology, a 2-aminoadipate transaminase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminoadipate transaminase
Thus, the two substrates of this enzyme are L-2-aminoadipate and 2-oxoglutarate, whereas its two products are 2-oxoadipate and L-glutamate.


2-aminoadipate transaminase
This enzyme belongs to the family of transferases, specifically the transaminases, which transfer nitrogenous groups. The systematic name of this enzyme class is L-2-aminoadipate:2-oxoglutarate aminotransferase. Other names in common use include alpha-aminoadipate aminotransferase, 2-aminoadipate aminotransferase, 2-aminoadipic aminotransferase, glutamic-ketoadipic transaminase, and glutamate-alpha-ketoadipate transaminase. This enzyme participates in lysine biosynthesis and lysine degradation. It employs one cofactor, pyridoxal phosphate.


2-aminoadipate transaminase, Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .


2-aminobenzenesulfonate 2,3-dioxygenase
In enzymology, a 2-aminobenzenesulfonate 2,3-dioxygenase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminobenzenesulfonate 2,3-dioxygenase
The 4 substrates of this enzyme are 2-aminobenzenesulfonate, NADH, H+, and O2, whereas its 3 products are 2,3-dihydroxybenzenesulfonate, NH3, and NAD+.


2-aminobenzenesulfonate 2,3-dioxygenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of two atoms o oxygen into the other donor. The systematic name of this enzyme class is 2-aminobenzenesulfonate,NADH:oxygen oxidoreductase (2,3-hydroxylating, ammonia-forming). This enzyme is also called 2-aminosulfobenzene 2,3-dioxygenase. This enzyme participates in benzoate degradation via hydroxylation.


2-aminoethylphosphonate—pyruvate transaminase
In enzymology, a 2-aminoethylphosphonate—pyruvate transaminase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminoethylphosphonate—pyruvate transaminase
Thus, the two substrates of this enzyme are (2-aminoethyl)phosphonate and pyruvate, whereas its two products are 2-phosphonoacetaldehyde and L-alanine.


2-aminoethylphosphonate—pyruvate transaminase
This enzyme belongs to the family of transferases, specifically the transaminases, which transfer nitrogenous groups. The systematic name of this enzyme class is (2-aminoethyl)phosphonate:pyruvate aminotransferase. Other names in common use include (2-aminoethyl)phosphonate transaminase, (2-aminoethyl)phosphonate aminotransferase, (2-aminoethyl)phosphonic acid aminotransferase, 2-aminoethylphosphonate-pyruvate aminotransferase, 2-aminoethylphosphonate aminotransferase, 2-aminoethylphosphonate transaminase, AEP transaminase, and AEPT. This enzyme participates in aminophosphonate metabolism. It employs one cofactor, pyridoxal phosphate.


2-aminoethylphosphonate—pyruvate transaminase, Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .


2-aminohexano-6-lactam racemase
In enzymology, a 2-aminohexano-6-lactam racemase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminohexano-6-lactam racemase
Hence, this enzyme has one substrate, L-2-aminohexano-6-lactam, and one product, D-2-aminohexano-6-lactam.


2-aminohexano-6-lactam racemase
This enzyme belongs to the family of isomerases, specifically those racemases and epimerases acting on amino acids and derivatives. The systematic name of this enzyme class is 2-aminohexano-6-lactam racemase. This enzyme is also called alpha-amino-epsilon-caprolactam racemase.


2-aminohexanoate transaminase
In enzymology, a 2-aminohexanoate transaminase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminohexanoate transaminase
Thus, the two substrates of this enzyme are L-2-aminohexanoate and 2-oxoglutarate, whereas its two products are 2-oxohexanoate and L-glutamate.


2-aminohexanoate transaminase
This enzyme belongs to the family of transferases, specifically the transaminases, which transfer nitrogenous groups. The systematic name of this enzyme class is L-2-aminohexanoate:2-oxoglutarate aminotransferase. Other names in common use include norleucine transaminase, norleucine (leucine) aminotransferase, and leucine L-norleucine: 2-oxoglutarate aminotransferase. It employs one cofactor, pyridoxal phosphate.


2-aminomuconate deaminase
In enzymology, a 2-aminomuconate deaminase (EC ) is an enzyme that catalyzes the chemical reaction


2-aminomuconate deaminase
Thus, the two substrates of this enzyme are 2-aminomuconate and H2O, whereas its two products are 4-oxalocrotonate and NH3.


2-aminomuconate deaminase
This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in compounds that have not been otherwise categorized within EC number 3.5. The systematic name of this enzyme class is 2-aminomuconate aminohydrolase. This enzyme participates in tryptophan metabolism.


2-bridge knot
In the mathematical field of knot theory, a 2-bridge knot is a knot which can be regular isotoped so that the natural height function given by the z-coordinate has only two maxima and two minima as critical points. Equivalently, these are the knots with bridge number 2, the smallest possible bridge number for a nontrivial knot.


2-bridge knot
Other names for 2-bridge knots are rational knots, 4-plats, and Viergeflechte (German for 'four braids'). 2-bridge links are defined similarly as above, but each component will have one min and max. 2-bridge knots were classified by Horst Schubert, using the fact that the 2-sheeted branched cover of the 3-sphere over the knot is a lens space.


2-bridge knot
The names rational knot and rational link were coined by John Conway who defined them as arising from numerator closures of rational tangles.


2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase
In enzymology, a 2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase (EC ) is an enzyme that catalyzes the chemical reaction


2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase
Hence, this enzyme has one substrate, cis-2-chloro-4-carboxymethylenebut-2-en-1,4-olide, and one product, trans-2-chloro-4-carboxymethylenebut-2-en-1,4-olide.


2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase
This enzyme belongs to the family of isomerases, specifically cis-trans isomerases. The systematic name of this enzyme class is 2-chloro-4-carboxymethylenebut-2-en-1,4-olide cis-trans-isomerase. Other names in common use include 2-chlorocarboxymethylenebutenolide isomerase, and chlorodienelactone isomerase. This enzyme participates in 1,4-dichlorobenzene degradation.


2-chlorobenzoate 1,2-dioxygenase
In enzymology, a 2-chlorobenzoate 1,2-dioxygenase (EC ) is an enzyme that catalyzes the chemical reaction


2-chlorobenzoate 1,2-dioxygenase
The 4 substrates of this enzyme are 2-chlorobenzoate, NADH, H+, and O2, whereas its 4 products are catechol, chloride, NAD+, and CO2.


2-chlorobenzoate 1,2-dioxygenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of two atoms o oxygen into the other donor. The systematic name of this enzyme class is 2-chlorobenzoate,NADH:oxygen oxidoreductase (1,2-hydroxylating, dechlorinating, decarboxylating). This enzyme is also called 2-halobenzoate 1,2-dioxygenase. This enzyme participates in benzoate degradation via coa ligation. It employs one cofactor, iron.


2-choice hashing
2-choice hashing, also known as 2-choice chaining, is "a variant of a hash table in which keys are added by hashing with two hash functions. The key is put in the array position with the fewer (colliding) keys. Some collision resolution scheme is needed, unless keys are kept in buckets. The average-case cost of a successful search is O(2+(m−1)/n){\displaystyle O(2+(m-1)/n)}, where m{\displaystyle m} is the number of keys and n{\displaystyle n} is the size of the array. The most collisions is log2lnn+θ(m/n){\displaystyle \log _{2}\ln n+\theta (m/n)} with high probability."


2-choice hashing, How It Works
2-choice hashing utilizes two hash functions h1(x) and h2(x) which work as hash functions are expected to work (i.e. mapping integers from the universe into a specified range). The two hash functions should be independent and have no correlation to each other. Having two hash functions allows any key x to have up to two potential locations to be stored based on the values of the respective outputs, h1(x) and  h2(x). It is important to note that, although there are two hash functions, there is only one table; both hash functions map to locations on that table.


2-choice hashing, Implementation
The most important functions of the hashing implementation in this case are insertion and search.


2-choice hashing, Performance
As is true with all hash tables, the performance is based on the largest bucket. Although there are instances where bucket sizes happen to be large based on the values and the hash functions used, this is rare. Having two hash functions and, therefore, two possible locations for any one value, makes the possibility of large buckets even more unlikely to happen.


2-choice hashing, Performance
The expected bucket size while using 2-choice hashing is: θ(log(log(n))). This improvement is due to the randomized concept known as The Power of Two Choices.


2-choice hashing, Performance
Using two hash functions offers substantial benefits over a single hash function. There is little improvement (and no change to the expected order statistics) if more than two hash functions are used: "Additional hash functions only decrease the maximum by a constant factor."


2-choice hashing, Performance
Some people recommend a type of 2-choice hashing called two-way skewed-associative cache in some CPU caches.


2-choice hashing, Performance
2-left hashing—using two hash tables of equal size n/2, and asymmetrically resolving ties by putting the key in the left hash table—has fewer collisions and therefore better performance than 2-choice hashing with one large hash table of size n.


2-coumarate O-beta-glucosyltransferase
In enzymology, a 2-coumarate O-beta-glucosyltransferase (EC ) is an enzyme that catalyzes the chemical reaction


2-coumarate O-beta-glucosyltransferase
Thus, the two substrates of this enzyme are UDP-glucose and trans-2-hydroxycinnamate, whereas its two products are UDP and trans-beta-D-glucosyl-2-hydroxycinnamate.


2-coumarate O-beta-glucosyltransferase
This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-glucose:trans-2-hydroxycinnamate O-beta-D-glucosyltransferase. Other names in common use include uridine diphosphoglucose-o-coumarate glucosyltransferase, and UDPG:o-coumaric acid O-glucosyltransferase. This enzyme participates in phenylpropanoid biosynthesis.


2-dehydro-3-deoxy-6-phosphogalactonate aldolase
In enzymology, a 2-dehydro-3-deoxy-6-phosphogalactonate aldolase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-6-phosphogalactonate aldolase
Hence, this enzyme has one substrate, 2-dehydro-3-deoxy-D-galactonate 6-phosphate, and two products, pyruvate and D-glyceraldehyde 3-phosphate.


2-dehydro-3-deoxy-6-phosphogalactonate aldolase
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 2-dehydro-3-deoxy-D-galactonate-6-phosphate D-glyceraldehyde-3-phosphate-lyase (pyruvate-forming). Other names in common use include 6-phospho-2-keto-3-deoxygalactonate aldolase, phospho-2-keto-3-deoxygalactonate aldolase, 2-keto-3-deoxy-6-phosphogalactonic aldolase, phospho-2-keto-3-deoxygalactonic aldolase, 2-keto-3-deoxy-6-phosphogalactonic acid aldolase, (KDPGal)aldolase, 2-dehydro-3-deoxy-D-galactonate-6-phosphate, and D-glyceraldehyde-3-phosphate-lyase. This enzyme participates in galactose metabolism.


2-dehydro-3-deoxy-6-phosphogalactonate aldolase, Structural studies
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes  and .


2-dehydro-3-deoxy-D-gluconate 5-dehydrogenase
In enzymology, a 2-dehydro-3-deoxy-D-gluconate 5-dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-D-gluconate 5-dehydrogenase
Thus, the two substrates of this enzyme are 2-dehydro-3-deoxy-D-gluconate and NAD+, whereas its 3 products are (4S)-4,6-dihydroxy-2,5-dioxohexanoate, NADH, and H+.


2-dehydro-3-deoxy-D-gluconate 5-dehydrogenase, Nomenclature
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 2-dehydro-3-deoxy-D-gluconate:NAD+ 5-oxidoreductase. Other names in common use include 2-keto-3-deoxygluconate 5-dehydrogenase, 2-keto-3-deoxy-D-gluconate dehydrogenase, 2-keto-3-deoxygluconate (nicotinamide adenine dinucleotide, (phosphate)) dehydrogenase, 2-keto-3-deoxy-D-gluconate (3-deoxy-D-glycero-2,5-hexodiulosonic, and acid) dehydrogenase.


2-dehydro-3-deoxy-D-gluconate 6-dehydrogenase
In enzymology, a 2-dehydro-3-deoxy-D-gluconate 6-dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-D-gluconate 6-dehydrogenase
Thus, the two substrates of this enzyme are 2-dehydro-3-deoxy-D-gluconate and NADP+, whereas its 3 products are (4S,5S)-4,5-dihydroxy-2,6-dioxohexanoate, NADPH, and H+.


2-dehydro-3-deoxy-D-gluconate 6-dehydrogenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 2-dehydro-3-deoxy-D-gluconate:NADP+ 6-oxidoreductase. Other names in common use include 2-keto-3-deoxy-D-gluconate dehydrogenase, and 2-keto-3-deoxygluconate dehydrogenase.


2-dehydro-3-deoxy-D-pentonate aldolase
In enzymology, a 2-dehydro-3-deoxy-D-pentonate aldolase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-D-pentonate aldolase
Hence, this enzyme has one substrate, 2-dehydro-3-deoxy-D-pentonate, and two products, pyruvate and glycolaldehyde.


2-dehydro-3-deoxy-D-pentonate aldolase
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 2-dehydro-3-deoxy-D-pentonate glycolaldehyde-lyase (pyruvate-forming). Other names in common use include 2-keto-3-deoxy-D-pentonate aldolase, 3-deoxy-D-pentulosonic acid aldolase, and 2-dehydro-3-deoxy-D-pentonate glycolaldehyde-lyase. This enzyme participates in pentose and glucuronate interconversions.


2-dehydro-3-deoxy-L-arabinonate dehydratase
In enzymology, a 2-dehydro-3-deoxy-L-arabinonate dehydratase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-L-arabinonate dehydratase
Hence, this enzyme has one substrate, 2-dehydro-3-deoxy-L-arabinonate, and two products, 2,5-dioxopentanoate and H2O.


2-dehydro-3-deoxy-L-arabinonate dehydratase
This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is 2-dehydro-3-deoxy-L-arabinonate hydro-lyase (2,5-dioxopentanoate-forming). Other names in common use include 2-keto-3-deoxy-L-arabinonate dehydratase, and 2-dehydro-3-deoxy-L-arabinonate hydro-lyase. This enzyme participates in ascorbate and aldarate metabolism.


2-dehydro-3-deoxy-L-pentonate aldolase
In enzymology, a 2-dehydro-3-deoxy-L-pentonate aldolase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxy-L-pentonate aldolase
Hence, this enzyme has one substrate, 2-dehydro-3-deoxy-L-pentonate, and two products, pyruvate and glycolaldehyde.


2-dehydro-3-deoxy-L-pentonate aldolase
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 2-dehydro-3-deoxy-L-pentonate glycolaldehyde-lyase (pyruvate-forming). Other names in common use include 2-keto-3-deoxy-L-pentonate aldolase, 2-keto-3-deoxy-L-arabonate aldolase, 2-keto-3-deoxy-D-xylonate aldolase, 3-deoxy-D-pentulosonic acid aldolase, and 2-dehydro-3-deoxy-L-pentonate glycolaldehyde-lyase. This enzyme participates in fructose and mannose metabolism.


2-dehydro-3-deoxygalactonokinase
In enzymology, a 2-dehydro-3-deoxygalactonokinase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxygalactonokinase
Thus, the two substrates of this enzyme are ATP and 2-dehydro-3-deoxy-D-galactonate, whereas its two products are ADP and 2-dehydro-3-deoxy-D-galactonate 6-phosphate.


2-dehydro-3-deoxygalactonokinase
This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:2-dehydro-3-deoxy-D-galactonate 6-phosphotransferase. Other names in common use include 2-keto-3-deoxygalactonokinase, 2-keto-3-deoxygalactonate kinase (phosphorylating), and 2-oxo-3-deoxygalactonate kinase. This enzyme participates in galactose metabolism.


2-dehydro-3-deoxyglucarate aldolase
In enzymology, a 2-dehydro-3-deoxyglucarate aldolase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxyglucarate aldolase
Hence, this enzyme has one substrate, 2-dehydro-3-deoxy-D-glucarate, and two products, pyruvate and tartronate semialdehyde.


2-dehydro-3-deoxyglucarate aldolase
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 2-dehydro-3-deoxy-D-glucarate tartronate-semialdehyde-lyase (pyruvate-forming). Other names in common use include 2-keto-3-deoxyglucarate aldolase, alpha-keto-beta-deoxy-D-glucarate aldolase, and 2-dehydro-3-deoxy-D-glucarate tartronate-semialdehyde-lyase. This enzyme participates in ascorbate and aldarate metabolism.


2-dehydro-3-deoxyglucarate aldolase, Structural studies
As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes , , , , , and .


2-dehydro-3-deoxygluconokinase
In enzymology, a 2-dehydro-3-deoxygluconokinase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydro-3-deoxygluconokinase
Thus, the two substrates of this enzyme are ATP and 2-dehydro-3-deoxy-D-gluconate, whereas its two products are ADP and 6-phospho-2-dehydro-3-deoxy-D-gluconate.


2-dehydro-3-deoxygluconokinase
This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:2-dehydro-3-deoxy-D-gluconate 6-phosphotransferase. Other names in common use include 2-keto-3-deoxygluconokinase, 2-keto-3-deoxy-D-gluconic acid kinase, 2-keto-3-deoxygluconokinase (phosphorylating), 2-keto-3-deoxygluconate kinase, and ketodeoxygluconokinase. This enzyme participates in pentose phosphate pathway and pentose and glucuronate interconversions.


2-dehydro-3-deoxygluconokinase, Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .


2-dehydropantoate 2-reductase
In enzymology, a 2-dehydropantoate 2-reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydropantoate 2-reductase
Thus, the two substrates of this enzyme are (R)-pantoate and NADP+, whereas its 3 products are 2-dehydropantoate, NADPH, and H+.


2-dehydropantoate 2-reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-pantoate:NADP+ 2-oxidoreductase. Other names in common use include 2-oxopantoate reductase, 2-ketopantoate reductase, 2-ketopantoic acid reductase, ketopantoate reductase, and ketopantoic acid reductase. This enzyme participates in pantothenate and coa biosynthesis.


2-dehydropantoate 2-reductase, Structural studies
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes , , , , and .


2-dehydropantoate aldolase
In enzymology, a 2-dehydropantoate aldolase (EC ) is an enzyme that catalyzes the chemical reaction:


2-dehydropantoate aldolase
Hence, this enzyme has one substrate, 2-dehydropantoate, and two products, 3-methyl-2-oxobutanoate and formaldehyde.


2-dehydropantoate aldolase
This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 2-dehydropantoate formaldehyde-lyase (3-methyl-2-oxobutanoate-forming). Other names in common use include ketopantoaldolase, and 2-dehydropantoate formaldehyde-lyase.


2-dehydropantolactone reductase (A-specific)
In enzymology, a 2-dehydropantolactone reductase (A-specific) (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydropantolactone reductase (A-specific)
Thus, the two substrates of this enzyme are (R)-pantolactone and NADP+, whereas its 3 products are 2-dehydropantolactone, NADPH, and H+.


2-dehydropantolactone reductase (A-specific)
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-pantolactone:NADP+ oxidoreductase (A-specific). Other names in common use include 2-oxopantoyl lactone reductase, ketopantoyl lactone reductase, 2-ketopantoyl lactone reductase, and 2-dehydropantoyl-lactone reductase (A-specific).


2-dehydropantolactone reductase (B-specific)
In enzymology, a 2-dehydropantolactone reductase (B-specific) (EC ) is an enzyme that catalyzes the chemical reaction


2-dehydropantolactone reductase (B-specific)
Thus, the two substrates of this enzyme are (R)-pantolactone and NADP+, whereas its 3 products are 2-dehydropantolactone, NADPH, and H+.


2-dehydropantolactone reductase (B-specific)
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-pantolactone:NADP+ oxidoreductase (B-specific). Other names in common use include 2-oxopantoyl lactone reductase, 2-ketopantoyl lactone reductase, ketopantoyl lactone reductase, and 2-dehydropantoyl-lactone reductase (B-specific).


2-deoxy-D-gluconate 3-dehydrogenase
2-deoxy-D-gluconate 3-dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction


2-deoxy-D-gluconate 3-dehydrogenase
Thus, the two substrates of this enzyme are 2-deoxy-D-gluconate and NAD+, whereas its 3 products are 3-dehydro-2-deoxy-D-gluconate, NADH, and H+.


2-deoxy-D-gluconate 3-dehydrogenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 2-deoxy-D-gluconate:NAD+ 3-oxidoreductase. This enzyme is also called 2-deoxygluconate dehydrogenase. This enzyme participates in pentose and glucuronate interconversions.


2-deoxy-D-gluconate 3-dehydrogenase, Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .


2-deoxy-scyllo-inosose synthase
2-deoxy-scyllo-inosose synthase (EC , btrC (gene), neoC (gene), kanC (gene)) is an enzyme with systematic name D-glucose-6-phosphate phosphate-lyase (2-deoxy-scyllo-inosose-forming). This enzyme catalyses the following chemical reaction


2-deoxyglucose-6-phosphatase
In enzymology, a 2-deoxyglucose-6-phosphatase (EC ) is an enzyme that catalyzes the chemical reaction


2-deoxyglucose-6-phosphatase
Thus, the two substrates of this enzyme are 2-deoxy-D-glucose 6-phosphate and H2O, whereas its two products are 2-deoxy-D-glucose and phosphate.


2-deoxyglucose-6-phosphatase
This enzyme belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds. The systematic name of this enzyme class is 2-deoxy-D-glucose-6-phosphate phosphohydrolase. This enzyme is also called 2-deoxyglucose-6-phosphate phosphatase.


2-deoxyglucosidase
In enzymology, a 2-deoxyglucosidase (EC ) is an enzyme that catalyzes the chemical reaction


2-deoxyglucosidase
Thus, the two substrates of this enzyme are 2-deoxy-alpha-D-glucoside and H2O, whereas its two products are 2-deoxy-D-glucose and alcohol.


2-deoxyglucosidase
This enzyme belongs to the family of hydrolases, specifically those glycosidases that hydrolyse O- and S-glycosyl compounds. The systematic name of this enzyme class is 2-deoxy-alpha-D-glucoside deoxyglucohydrolase. Other names in common use include 2-deoxy-alpha-glucosidase, and 2-deoxy-alpha-D-glucosidase.


2-enoate reductase
In enzymology, a 2-enoate reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-enoate reductase
Thus, the two substrates of this enzyme are butanoate and NAD+, whereas its 3 products are 2-butenoate, NADH, and H+.


2-enoate reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is butanoate:NAD+ Delta2-oxidoreductase. This enzyme is also called enoate reductase. This enzyme participates in phenylalanine metabolism. It has 4 cofactors: FAD, Iron, Sulfur,  and Iron-sulfur.


2-ethylmalate synthase
In enzymology, a 2-ethylmalate synthase (EC ) is an enzyme that catalyzes the chemical reaction


2-ethylmalate synthase
The 3 substrates of this enzyme are acetyl-CoA, H2O, and 2-oxobutanoate, whereas its two products are (R)-2-ethylmalate and CoA.


2-ethylmalate synthase
This enzyme belongs to the family of transferases, specifically those acyltransferases that convert acyl groups into alkyl groups on transfer. The systematic name of this enzyme class is acetyl-CoA:2-oxobutanoate C-acetyltransferase (thioester-hydrolysing, carboxymethyl-forming). Other names in common use include (R)-2-ethylmalate 2-oxobutanoyl-lyase (CoA-acetylating), 2-ethylmalate-3-hydroxybutanedioate synthase, propylmalate synthase, and propylmalic synthase. This enzyme participates in pyruvate metabolism.


2-factor theorem
In the mathematical discipline of graph theory, the 2-factor theorem, discovered by Julius Petersen, is one of the earliest works in graph theory. It can be stated as follows:


2-factor theorem
Here, a 2-factor is a subgraph of G in which all vertices have degree two; that is, it is a collection of cycles that together touch each vertex exactly once.


2-factor theorem, Proof
In order to prove this generalized form of the theorem, Petersen first proved that a 4-regular graph can be factorized into two 2-factors by taking alternate edges in a Eulerian trail. He noted that the same technique used for the 4-regular graph yields a factorization of a 2k-regular graph into two k-factors.


2-factor theorem, Proof
To prove this theorem, it is sufficient to consider connected graphs. A connected graph with even degree has an Eulerian trail. Traversing this Eulerian trail generates an orientation D of G such that every point has indegree and outdegree = k. Next, replace every vertex v ϵ V(D) by two vertices v’ and v”, and replace every directed edge uv of the oriented graph by an undirected edge from u’ to v”. Since D has in- and outdegree equal to k the resulting bipartite graph G’ is k-regular. The edges of G’ can be partitioned into k perfect matchings by a theorem of Kőnig. Now merging v’ with v” for every v recover the graph G, and maps the k perfect matchings of G’ onto k 2-factors of G which partition its edges. [ 1]


2-factor theorem, History
The theorem was discovered by Julius Petersen, a Danish mathematician. It is in fact, one of the first results in graph theory. The theorem appears first in the 1891 article "Die Theorie der regulären graphs". To prove the theorem Petersen's fundamental idea was to 'colour' the edges of a trial or a path alternatingly red and blue, and then to use the edges of one or both colours for the construction of other paths or trials.


2-functor
In mathematics, a 2-functor is a morphism between 2-categories. They may be defined formally using enrichment by saying that a 2-category is exactly a Cat-enriched category and a 2-functor is a Cat-functor.


2-functor
Explicitly, if C and D are 2-categories then a 2-functor F:C→D{\displaystyle F\colon C\to D} consists of


2-functor
such that each Fc,c{\displaystyle F_{c,c}} strictly preserves identity objects and they commute with horizontal composition in C and D.


2-furoate—CoA ligase
In enzymology, a 2-furoate—CoA ligase (EC ) is an enzyme that catalyzes the chemical reaction


2-furoate—CoA ligase
The 3 substrates of this enzyme are ATP, 2-furoate, and CoA, whereas its 3 products are AMP, diphosphate, and 2-furoyl-CoA.


2-furoate—CoA ligase
This enzyme belongs to the family of ligases, specifically those forming carbon-sulfur bonds as acid-thiol ligases. The systematic name of this enzyme class is 2-furoate:CoA ligase (AMP-forming). This enzyme is also called 2-furoyl coenzyme A synthetase.


2-furoyl-CoA dehydrogenase
In enzymology, a 2-furoyl-CoA dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction


2-furoyl-CoA dehydrogenase
The 3 substrates of this enzyme are 2-furoyl-CoA, H2O, and acceptor, whereas its two products are S-(5-hydroxy-2-furoyl)-CoA and reduced acceptor.


2-furoyl-CoA dehydrogenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with other acceptors. The systematic name of this enzyme class is 2-furoyl-CoA:acceptor 5-oxidoreductase (hydroxylating). Other names in common use include furoyl-CoA hydroxylase, 2-furoyl coenzyme A hydroxylase, 2-furoyl coenzyme A dehydrogenase, and 2-furoyl-CoA:(acceptor) 5-oxidoreductase (hydroxylating). It employs one cofactor, copper.


2-group
In mathematics, a 2-group, or 2-dimensional higher group, is a certain combination of group and groupoid. The 2-groups are part of a larger hierarchy of n-groups. In some of the literature, 2-groups are also called gr-categories or groupal groupoids.


2-group, Definition
A 2-group is a monoidal category G in which every morphism is invertible and every object has a weak inverse. (Here, a weak inverse of an object x is an object y such that xy and yx are both isomorphic to the unit object.)


2-group, Strict 2-groups
Much of the literature focuses on strict 2-groups. A strict 2-group is a strict monoidal category in which every morphism is invertible and every object has a strict inverse (so that xy and yx are actually equal to the unit object).


2-group, Strict 2-groups
A strict 2-group is a group object in a category of categories; as such, they are also called groupal categories. Conversely, a strict 2-group is a category object in the category of groups; as such, they are also called categorical groups. They can also be identified with crossed modules, and are most often studied in that form. Thus, 2-groups in general can be seen as a weakening of crossed modules.


2-group, Strict 2-groups
Every 2-group is equivalent to a strict 2-group, although this can't be done coherently: it doesn't extend to 2-group homomorphisms.


2-group, Properties
Weak inverses can always be assigned coherently: one can define a functor on any 2-group G that assigns a weak inverse to each object and makes that object an adjoint equivalence in the monoidal category G.


2-group, Properties
Given a bicategory B and an object x of B, there is an automorphism 2-group of x in B, written AutB(x). The objects are the automorphisms of x, with multiplication given by composition, and the morphisms are the invertible 2-morphisms between these. If B is a 2-groupoid (so all objects and morphisms are weakly invertible) and x is its only object, then AutB(x) is the only data left in B. Thus, 2-groups may be identified with one-object 2-groupoids, much as groups may be identified with one-object groupoids and monoidal categories may be identified with one-object bicategories.


2-group, Properties
If G is a strict 2-group, then the objects of G form a group, called the underlying group of G and written G0. This will not work for arbitrary 2-groups; however, if one identifies isomorphic objects, then the equivalence classes form a group, called the fundamental group of G and written π1(G). (Note that even for a strict 2-group, the fundamental group will only be a quotient group of the underlying group.)


2-group, Properties
As a monoidal category, any 2-group G has a unit object IG. The automorphism group of IG is an abelian group by the Eckmann–Hilton argument, written Aut(IG) or π2(G).


2-group, Properties
The fundamental group of G acts on either side of π2(G), and the associator of G (as a monoidal category) defines an element of the cohomology group H3(π1(G),π2(G)). In fact, 2-groups are classified in this way: given a group π1, an abelian group π2, a group action of π1 on π2, and an element of H3(π1,π2), there is a unique (up to equivalence) 2-group G with π1(G) isomorphic to π1, π2(G) isomorphic to π2, and the other data corresponding.


2-group, Properties
The element of H3(π1,π2) associated to a 2-group is sometimes called its Sinh invariant, as it was developed by Grothendieck's student Hoàng Xuân Sính.


2-group, Fundamental 2-group
Given a topological space X and a point x in that space, there is a fundamental 2-group of X at x, written Π2(X,x). As a monoidal category, the objects are loops at x, with multiplication given by concatenation, and the morphisms are basepoint-preserving homotopies between loops, with these morphisms identified if they are themselves homotopic.


2-group, Fundamental 2-group
Conversely, given any 2-group G, one can find a unique (up to weak homotopy equivalence) pointed connected space (X,x) whose fundamental 2-group is G and whose homotopy groups πn are trivial for n > 2. In this way, 2-groups classify pointed connected weak homotopy 2-types. This is a generalisation of the construction of Eilenberg–Mac Lane spaces.


2-group, Fundamental 2-group
If X is a topological space with basepoint x, then the fundamental group of X at x is the same as the fundamental group of the fundamental 2-group of X at x; that is,


2-group, Fundamental 2-group
This fact is the origin of the term "fundamental" in both of its 2-group instances.


2-group, Fundamental 2-group
Thus, both the first and second homotopy groups of a space are contained within its fundamental 2-group. As this 2-group also defines an action of π1(X,x) on π2(X,x) and an element of the cohomology group H3(π1(X,x),π2(X,x)), this is precisely the data needed to form the Postnikov tower of X if X is a pointed connected homotopy 2-type.


2-haloacid dehalogenase (configuration-inverting)
2-haloacid dehalogenase (configuration-inverting) (EC , 2-haloalkanoic acid dehalogenase, 2-haloalkanoid acid halidohydrolase, DL-2-haloacid dehalogenase, DL-2-haloacid dehalogenase (inversion of configuration), DL-2-haloacid halidohydrolase (inversion of configuration), DL-DEXi, (R,S)-2-haloacid dehalogenase (configuration-inverting)) is an enzyme with systematic name (S)-2-haloacid dehalogenase (configuration-inverting). This enzyme catalyses the following chemical reaction


2-haloacid dehalogenase (configuration-retaining)
2-haloacid dehalogenase (configuration-retaining) (EC , 2-haloalkanoic acid dehalogenase, 2-haloalkanoid acid halidohydrolase, DL-2-haloacid dehalogenase, DL-DEXr) is an enzyme with systematic name (S)-2-haloacid dehalogenase (configuration-retaining). This enzyme catalyses the following chemical reaction


2-haloacid dehalogenase (configuration-retaining)
Dehalogenates both (S)- and (R)-2-haloalkanoic acids to the corresponding (S)- and (R)-hydroxyalkanoic acids.


2-hexadecenal reductase
In enzymology, a 2-hexadecenal reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-hexadecenal reductase
Thus, the two substrates of this enzyme are hexadecanal and NADP+, whereas its 3 products are 2-trans-hexadecenal, NADPH, and H+.


2-hexadecenal reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is hexadecanal:NADP+ Delta2-oxidoreductase. Other names in common use include 2-alkenal reductase, and hexadecanal: NADP+ oxidoreductase.


2-hydroxy-1,4-benzoquinone reductase
In enzymology, a 2-hydroxy-1,4-benzoquinone reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxy-1,4-benzoquinone reductase
The 3 substrates of this enzyme are 2-hydroxy-1,4-benzoquinone, NADH, and H+, whereas its two products are 1,2,4-trihydroxybenzene and NAD+.


2-hydroxy-1,4-benzoquinone reductase, Nomenclature
This enzyme belongs to the family of oxidoreductases, specifically those acting on NADH or NADPH with a quinone or similar compound as acceptor. The systematic name of this enzyme class is 2-hydroxy-1,4-benzoquinone:NADH oxidoreductase. Other names in common use include hydroxybenzoquinone reductase, 1,2,4-trihydroxybenzene:NAD oxidoreductase, and NADH:2-hydroxy-1,4-benzoquinone oxidoreductase.


2-hydroxy-3-keto-5-methylthiopentenyl-1-phosphate phosphatase
2-hydroxy-3-keto-5-methylthiopentenyl-1-phosphate phosphatase (EC , HK-MTPenyl-1-P phosphatase, MtnX, YkrX) is an enzyme with systematic name 2-hydroxy-5-(methylthio)-3-oxopent-1-enyl phosphate phosphohydrolase. This enzyme catalyses the following chemical reaction


2-hydroxy-3-keto-5-methylthiopentenyl-1-phosphate phosphatase
The enzyme participates in the methionine salvage pathway in Bacillus subtilis.


2-hydroxy-3-oxoadipate synthase
In enzymology, a 2-hydroxy-3-oxoadipate synthase (EC ) is an enzyme that catalyzes the following chemical reaction:


2-hydroxy-3-oxoadipate synthase
The two substrates of this enzyme are 2-oxoglutarate and glyoxylate, whereas its two products are 2-hydroxy-3-oxoadipate and CO2.


2-hydroxy-3-oxoadipate synthase
This enzyme belongs to the family of transferases, specifically those transferring aldehyde or ketonic groups (transaldolases and transketolases, respectively). Other names in common use include 2-hydroxy-3-oxoadipate glyoxylate-lyase (carboxylating), alpha-ketoglutaric-glyoxylic carboligase, and oxoglutarate: glyoxylate carboligase. This enzyme participates in glyoxylate and dicarboxylate metabolism. It employs one cofactor, thiamin diphosphate.


2-hydroxy-3-oxopropionate reductase
In enzymology, a 2-hydroxy-3-oxopropionate reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxy-3-oxopropionate reductase
The 3 substrates of this enzyme are (R)-glycerate, NAD+, and NADP+, whereas its 4 products are 2-hydroxy-3-oxopropanoate, NADH, NADPH, and H+.


2-hydroxy-3-oxopropionate reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-glycerate:NAD(P)+ oxidoreductase. This enzyme is also called tartronate semialdehyde reductase. This enzyme participates in glyoxylate and dicarboxylate metabolism.


2-hydroxy-3-oxopropionate reductase, Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .


2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase
2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase (EC , 2-hydroxy-4-carboxymuconate 6-semialdehyde dehydrogenase, 4-carboxy-2-hydroxy-cis,cis-muconate-6-semialdehyde:NADP+ oxidoreductase, alpha-hydroxy-gamma-carboxymuconic epsilon-semialdehyde dehydrogenase, 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase, LigC, ProD) is an enzyme with systematic name 4-carboxy-2-hydroxymuconate semialdehyde hemiacetal:NADP+ 2-oxidoreductase. This enzyme catalyses the following chemical reaction


2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase
Unsubstituted aliphatic or aromatic aldehydes or glucose cannot serve as substrate of this enzyme.


2-hydroxy-6-oxo-6-(2-aminophenyl)hexa-2,4-dienoate hydrolase
2-hydroxy-6-oxo-6-(2-aminophenyl)hexa-2,4-dienoate hydrolase (EC , CarC) is an enzyme with systematic name (2E,4E)-6-(2-aminophenyl)-2-hydroxy-6-oxohexa-2,4-dienoate acylhydrolase. This enzyme catalyses the following chemical reaction


2-hydroxy-6-oxo-6-(2-aminophenyl)hexa-2,4-dienoate hydrolase
This enzyme catalyses the third step in the aerobic degradation pathway of carbazole.


2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate reductase
This is the current revision of this page, as edited by OAbot (talk | contribs) at 08:36, 15 April 2020 (Open access bot: doi added to citation with #oabot.). The present address (URL) is a permanent link to this version.


2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate reductase
In enzymology, a 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate reductase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate reductase
Thus, the two substrates of this enzyme are 2,6-dioxo-6-phenylhexanoate and NADP+, whereas its 3 products are 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate, NADPH, and H+.


2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate reductase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 2,6-dioxo-6-phenylhexanoate:NADP+ Delta2-oxidoreductase. Other names in common use include 2-hydroxy-6-oxo-phenylhexa-2,4-dienoate (reduced nicotinamide, and adenine dinucleotide phosphate) reductase.


2-hydroxy-6-oxonona-2,4-dienedioate hydrolase
2-hydroxy-6-oxonona-2,4-dienedioate hydrolase (EC , mhpC (gene)) is an enzyme with systematic name (2Z,4E)-2-hydroxy-6-oxona-2,4-dienedioate succinylhydrolase. This enzyme catalyses the following chemical reaction:


2-hydroxy-6-oxonona-2,4-dienedioate hydrolase
This enzyme catalyses a step in a pathway of phenylpropanoid compounds degradation.


2-hydroxy-dATP diphosphatase
2-hydroxy-dATP diphosphatase (EC , also known as oxidized purine nucleoside triphosphatase, or (2'-deoxy) ribonucleoside 5'-triphosphate pyrophosphohydrolase, or Nudix hydrolase 1 (NUDT1), or MutT homolog 1 (MTH1), or 7,8-dihydro-8-oxoguanine triphosphatase) is an enzyme that in humans is encoded by the NUDT1 gene. During DNA repair, the enzyme hydrolyses oxidized purines and prevents their addition onto the DNA chain. As such it has important role in aging and cancer development.


2-hydroxy-dATP diphosphatase, Function
The enzyme hydrolyses oxidized purine nucleoside triphosphates. The enzyme is used in DNA repair, where it hydrolysis the oxidized purines and prevents their addition onto the DNA chain.


2-hydroxy-dATP diphosphatase, Function
Misincorporation of oxidized nucleoside triphosphates into DNA and/or RNA during replication and transcription can cause mutations that may result in carcinogenesis or neurodegeneration. First isolated from Escherichia coli because of its ability to prevent occurrence of 8-oxoguanine in DNA, the protein encoded by this gene is an enzyme that hydrolyzes oxidized purine nucleoside triphosphates, such as 8-oxo-dGTP, 8-oxo-dATP, 2-oxo-dATP, 2-hydroxy-dATP, and 2-hydroxy rATP, to monophosphates, thereby preventing misincorporation.


2-hydroxy-dATP diphosphatase, Function
MutT enzymes in non-human organisms often have substrate specificity for certain types of oxidized nucleotides, such as that of E. coli, which is specific to 8-oxoguanine nucleotides. Human MTH1, however, has substrate specificity for a much broader range of oxidatively damaged nucleotides. The mechanism of hMTH1's broad specificity for these oxidized nucleotides is derived from their recognition in the enzyme's substrate binding pocket due to an exchange of protonation state between two nearby aspartate residues.


2-hydroxy-dATP diphosphatase, Function
The encoded protein is localized mainly in the cytoplasm, with some in the mitochondria, suggesting that it is involved in the sanitization of nucleotide pools both for nuclear and mitochondrial genomes. In plants, MTH1 has also been shown to enhance resistance to heat- and paraquat-induced oxidative stress, resulting in fewer dead cells and less accumulation of hydrogen peroxide.


2-hydroxy-dATP diphosphatase, Function
Several alternatively spliced transcript variants, some of which encode distinct isoforms, have been identified. Additional variants have been observed, but their full-length natures have not been determined. A single-nucleotide polymorphism that results in the production of an additional, longer isoform has been described.


2-hydroxy-dATP diphosphatase, Research, Aging
A mouse model has been studied that over-expresses hMTH1-Tg (NUDT1). The hMTH1-Tg mice express high levels of the hMTH1 hydrolase that degrades 8-oxodGTP and 8-oxoGTP and therefore excludes 8-oxoguanine from DNA and RNA. The steady state levels of 8-oxoguanine in DNA of several organs including the brain are significantly reduced in hMTH1-Tg over-expressing mice. Conversely, MTH1-null mice exhibit a significantly higher level of 8-oxo-dGTP accumulation than that of the wild type. Over-expression of hMTH1 prevents the age-dependent accumulation of DNA 8-oxoguanine that occurs in wild-type mice. The lower levels of oxidized guanines are associated with greater longevity. The hMTH1-Tg animals have a significantly longer lifespan than their wild-type littermates. These findings provide a link between ageing and oxidative DNA damage (see DNA damage theory of aging).


2-hydroxy-dATP diphosphatase, Research, Cancer
Studies have suggested that this enzyme plays a role in both preventing the formation of cancer cells and the proliferation of cancer cells. This makes it a topic of interest in cancer research, both as a potential method for healthy cells to prevent cancer and a weakness to target within existing cancer cells.


2-hydroxy-dATP diphosphatase, Research, Cancer
Eliminating the MTH1 gene in mice results in over three times more mice developing tumors compared to a control group. The enzyme's much-studied ability to sanitize a cell's nucleotide pool prevents it from developing mutations, including cancerous ones. Specifically, another study found that MTH1 inhibition in cancer cells leads to incorporation of 8-oxo-dGTP and other oxidatively damaged nucleotides into the cell's DNA, damaging it and causing cell death. However, cancer cells have also been shown to benefit from use of MTH1. Cells from malignant breast tumors exhibit extreme MTH1 expression compared to other human cells.


2-hydroxy-dATP diphosphatase, Research, Cancer
Because a cancer cell divides much more rapidly than a normal human cell, it is far more in need of an enzyme like MTH1 that prevents fatal mutations during replication. This property of cancer cells could allow for monitoring of cancer treatment efficacy by measuring MTH1 expression. Development of suitable probes for this purpose is currently underway.


2-hydroxy-dATP diphosphatase, Research, Cancer
Disagreement exists concerning MTH1's functionality relative to prevention of DNA damage and cancer. Subsequent studies have had difficulty reproducing previously reported cytotoxic or antiproliferation effects of MTH1 inhibition on cancer cells, even calling into question whether MTH1 truly does serve to remove oxidatively damaged nucleotides from a cell's nucleotide pool. One study of newly discovered MTH1 inhibitors suggests that these anticancer properties exhibited by the older MTH1 inhibitors may be due to off-target cytotoxic effects. After revisiting the experiment, the original authors of this claim found that while the original MTH1 inhibitors in question lead to damaged nucleotides being incorporated into DNA, they demonstrate the others that do not induce toxicity fail to introduce the DNA lesion. Research into this topic is ongoing.


2-hydroxy-dATP diphosphatase, Research, As a drug target
MTH1 is a potential drug target to treat cancer, however there are conflicting results regarding the cytotoxicity of MTH1 inhibitors toward cancer cells.


2-hydroxy-dATP diphosphatase, Research, As a drug target
Karonudib, an MTH1 inhibitor, is currently being evaluated a phase I clinical trial for safety and tolerability.


2-hydroxy-dATP diphosphatase, Research, As a drug target
A potent and selective MTH1 inhibitor AZ13792138 has been developed by AstraZeneca has been made available as a chemical probe to academic researchers. However AstraZeneca has found that neither AZ13792138 nor genetic knockdown of MTH1 displays any significant cytotoxicity to cancer cells.


2-hydroxybiphenyl 3-monooxygenase
In enzymology, a 2-hydroxybiphenyl 3-monooxygenase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxybiphenyl 3-monooxygenase
The 4 substrates of this enzyme are 2-hydroxybiphenyl, NADH, H+, and O2, whereas its 3 products are 2,3-dihydroxybiphenyl, NAD+, and H2O.


2-hydroxybiphenyl 3-monooxygenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is 2-hydroxybiphenyl,NADH:oxygen oxidoreductase (3-hydroxylating).


2-hydroxychromene-2-carboxylate isomerase
2-hydroxychromene-2-carboxylate isomerase (EC , HCCA isomerase, 2HC2CA isomerase, 2-hydroxychromene-2-carboxylic acid isomerase) is an enzyme with systematic name 2-hydroxy-2H-chromene-2-carboxylate---(3E)-4-(2-hydroxyphenyl)-2-oxobut-3-enoate isomerase. This enzyme catalyses the following chemical reaction


2-hydroxycyclohexanone 2-monooxygenase
In enzymology, a 2-hydroxycyclohexanone 2-monooxygenase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxycyclohexanone 2-monooxygenase
The 4 substrates of this enzyme are 2-hydroxycyclohexan-1-one, NADPH, H+, and O2, whereas its 3 products are 6-hydroxyhexan-6-olide, NADP+, and H2O.


2-hydroxycyclohexanone 2-monooxygenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is 2-hydroxycyclohexan-1-one,NADPH:oxygen 2-oxidoreductase (1,2-lactonizing).


2-hydroxyethylphosphonate dioxygenase
2-hydroxyethylphosphonate dioxygenase (EC , HEPD, phpD (gene)) is an enzyme with systematic name 2-hydroxyethylphosphonate:O2 1,2-oxidoreductase (hydroxymethylphosphonate forming). This enzyme catalyses the following chemical reaction


2-hydroxyglutarate synthase
In enzymology, a 2-hydroxyglutarate synthase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxyglutarate synthase
The 3 substrates of this enzyme are propanoyl-CoA, H2O, and glyoxylate, whereas its two products are 2-hydroxyglutarate and CoA.


2-hydroxyglutarate synthase
This enzyme belongs to the family of transferases, specifically those acyltransferases that convert acyl groups into alkyl groups on transfer. The systematic name of this enzyme class is propanoyl-CoA:glyoxylate C-propanoyltransferase (thioester-hydrolysing, 2-carboxyethyl-forming). Other names in common use include 2-hydroxyglutaratic synthetase, 2-hydroxyglutaric synthetase, alpha-hydroxyglutarate synthase, hydroxyglutarate synthase, and 2-hydroxyglutarate glyoxylate-lyase (CoA-propanoylating). This enzyme participates in c5-branched dibasic acid metabolism.


2-hydroxyhexa-2,4-dienoate hydratase
2-hydroxyhexa-2,4-dienoate hydratase (EC , tesE (gene), hsaE (gene)) is an enzyme with systematic name 4-hydroxy-2-oxohexanoate hydro-lyase ((2Z,4Z)-2-hydroxyhexa-2,4-dienoate-forming). This enzyme catalyses the following chemical reaction


2-hydroxyhexa-2,4-dienoate hydratase
This enzyme catalyses a late step in the bacterial steroid degradation pathway.


2-hydroxyisoflavanone dehydratase
In enzymology, a 2-hydroxyisoflavanone dehydratase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxyisoflavanone dehydratase
Hence, this enzyme has one substrate, 2,7,4'-trihydroxyisoflavanone, and two products, daidzein and H2O.


2-hydroxyisoflavanone dehydratase
This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is 2,7,4'-trihydroxyisoflavanone hydro-lyase (daidzein-forming). This enzyme is also called 2,7,4'-trihydroxyisoflavanone hydro-lyase. This enzyme participates in isoflavonoid biosynthesis.


2-hydroxyisoflavanone dehydratase
The variant GmHID1 from Glycine max converts 2-hydroxyisoflavone to isoflavones, mostly daidzein and genistein.


2-hydroxymethylglutarate dehydrogenase
In enzymology, a 2-hydroxymethylglutarate dehydrogenase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxymethylglutarate dehydrogenase
Thus, the two substrates of this enzyme are (S)-2-hydroxymethylglutarate and NAD+, whereas its 3 products are 2-formylglutarate, NADH, and H+.


2-hydroxymethylglutarate dehydrogenase
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-2-hydroxymethylglutarate:NAD+ oxidoreductase. This enzyme is also called HgD.


2-hydroxymuconate tautomerase
2-hydroxymuconate tautomerase (EC , 4-oxalocrotonate tautomerase, 4-oxalocrotonate isomerase, cnbG (gene), praC (gene), xylH (gene)) is an enzyme with systematic name (2Z,4E)-2-hydroxyhexa-2,4-dienedioate keto-enol isomerase. This enzyme catalyses the following chemical reaction


2-hydroxymuconate tautomerase
Involved in the meta-cleavage pathway for the degradation of phenols, modified phenols and catechols.


2-hydroxymuconate-semialdehyde hydrolase
In enzymology, a 2-hydroxymuconate-semialdehyde hydrolase (EC ) is an enzyme that catalyzes the chemical reaction


2-hydroxymuconate-semialdehyde hydrolase
Thus, the two substrates of this enzyme are 2-hydroxymuconate semialdehyde and H2O, whereas its two products are formate and 2-oxopent-4-enoate.


2-hydroxymuconate-semialdehyde hydrolase
This enzyme belongs to the family of hydrolases, specifically those acting on carbon-carbon bonds in ketonic substances. The systematic name of this enzyme class is 2-hydroxymuconate-semialdehyde formylhydrolase. Other names in common use include 2-hydroxy-6-oxohepta-2,4-dienoate hydrolase, 2-hydroxymuconic semialdehyde hydrolase, HMSH, and HOD hydrolase. This enzyme participates in 5 metabolic pathways: benzoate degradation via hydroxylation, toluene and xylene degradation, 1,4-dichlorobenzene degradation, carbazole degradation, and styrene degradation.


2-hydroxymuconate-semialdehyde hydrolase, Structural studies
As of late 2007, 10 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , and .


2-hydroxyphytanoyl-CoA lyase
2-Hydroxyphytanoyl-CoA lyase is a peroxisomal enzyme involved in the catabolism of phytanoic acid by α-oxidation. It requires thiamine diphosphate (ThDP) as cofactor.


2-hydroxypropyl-CoM lyase
2-hydroxypropyl-CoM lyase (EC , epoxyalkane:coenzyme M transferase, epoxyalkane:CoM transferase, epoxyalkane:2-mercaptoethanesulfonate transferase, coenzyme M-epoxyalkane ligase, epoxyalkyl:CoM transferase, epoxypropane:coenzyme M transferase, epoxypropyl:CoM transferase, EaCoMT, 2-hydroxypropyl-CoM:2-mercaptoethanesulfonate lyase (epoxyalkane-ring-forming), (R)-2-hydroxypropyl-CoM 2-mercaptoethanesulfonate lyase (cyclizing, (R)-1,2-epoxypropane-forming)) is an enzyme with systematic name (R)-(or (S)-)2-hydroxypropyl-CoM:2-mercaptoethanesulfonate lyase (epoxyalkane-ring-forming). This enzyme catalyses the following chemical reaction