Cobalt chelatase Cobalt chelatase Cobalt chelatase () is an enzyme that catalyzes the chemical reaction The 4 substrates of this enzyme are ATP, hydrogenobyrinic acid a,c-diamide, Co, and HO, whereas its 4 products are ADP, phosphate, cob(II)yrinic acid a,c-diamide, and H. The aerobic cobalt chelatase (aerobic cobalamin biosynthesis pathway) consists of three subunits, CobT, CobN () and CobS (). Cobalamin (vitamin B12) can be complexed with metal via the ATP-dependent reactions (aerobic pathway) (e.g., in "Pseudomonas denitrificans") or via ATP-independent reactions (anaerobic pathway) (e.g., in "Salmonella typhimurium"). The corresponding cobalt chelatases are not homologous. However, aerobic cobalt chelatase subunits CobN and CobS
Chemical element hydrogen and deuterium). Thus, all carbon isotopes have nearly identical chemical properties because they all have six protons and six electrons, even though carbon atoms may, for example, have 6 or 8 neutrons. That is why the atomic number, rather than mass number or atomic weight, is considered the identifying characteristic of a chemical element. The symbol for atomic number is "Z". Isotopes are atoms of the same element (that is, with the same number of protons in their atomic nucleus), but having "different" numbers of neutrons. Thus, for example, there are three main isotopes of carbon. All carbon atoms