flavin-containing monooxygenase 3 flavin-containing monooxygenase 3 flavin-containing monooxygenase 3 (fmo3), also known as dimethylaniline monooxygenase 3 and trimethylamine monooxygenase, is a flavoprotein enzyme (ec 1.14.13.148) that in humans is encoded by the fmo3 gene. this enzyme catalyzes the following chemical reaction, among others: trimethylamine + nadph + h+ + o2 ⇌ trimethylamine n-oxide + nadp+ + h2o fmo3identifiersaliasesfmo3, trimethylamine monooxygenase, flavin-containing monooxygenase 3, dimethylaniline monooxygenase 3, fmoii, tmau, dj127d3.1, flavin containing monooxygenase 3, flavin containing dimethylaniline monoxygenase 3external idsomim: 136132 mgi: 1100496 homologene: 128199 genecards: fmo3 ec number1.14.13.148gene location (human)chr.chromosome 1 (human)band1q24.3start171,090,901 bpend171,117,819 bpgene location (mouse)chr.chromosome 1 (mouse)band1 h2.1|1 70.34 cmstart162,781,369 bpend162,812,097 bprna expression patternbgeehumanmouse (ortholog)top expressed inright lobe of liverright lungsubcutaneous adipose tissuebronchial epithelial cellupper lobe of left lungright uterine tubevisceral pleuralower lobe of lungachilles tendonleft uterine tubetop expressed inright lung lobetracheasuperior surface of tongueolfactory epitheliumascending aortaaortic valvecarotid bodylacrimal glandoocytesecondary oocytemore reference expression databiogpsmore reference expression datagene ontologymolecular function trimethylamine monooxygenase activity oxidoreductase activity n,n-dimethylaniline monooxygenase activity nadp binding flavin adenine dinucleotide binding monooxygenase activity protein binding cellular component integral component of membrane organelle membrane endoplasmic reticulum membrane intracellular membrane-bounded organelle endoplasmic reticulum membrane biological process xenobiotic metabolic process sources:amigo / quickgoorthologsspecieshumanmouseentrez232814262ensemblensg00000007933ensmusg00000026691uniprotp31513p97501refseq (mrna)nm_001002294nm_006894nm_001319173nm_001319174nm_008030refseq (protein)np_001002294np_001306102np_001306103np_008825np_032056location (ucsc)chr 1: 171.09 – 171.12 mbchr 1: 162.78 – 162.81 mbpubmed searchwikidataview/edit humanview/edit mouse fmo3 is the main flavin-containing monooxygenase isoenzyme that is expressed in the liver of adult humans. the human fmo3 enzyme catalyzes several types of reactions, including: the n-oxygenation of primary, secondary, and tertiary amines; the s-oxygenation of nucleophilic sulfur-containing compounds; and the 6-methylhydroxylation of the anti-cancer agent dimethylxanthenone acetic acid (dmxaa). fmo3 is the primary enzyme in humans which catalyzes the n-oxidation of trimethylamine into trimethylamine n-oxide; fmo1 also does this, but to a much lesser extent than fmo3. genetic deficiencies of the fmo3 enzyme cause primary trimethylaminuria, also known as "fish odor syndrome". fmo3 is also involved in the metabolism of many xenobiotics (i.e., exogenous compounds which are not normally present in the body), such as the oxidative deamination of amphetamine. ligands list of human fmo3 substrates, inhibitors, inducers, and activators fmo3 substrates fmo3 inhibitors fmo3 inducers fmo3 activators endogenous biomolecules epinephrine norepinephrine phenethylamine† trimethylamine† tyramine notable exogenous xenobiotics amphetamine† and its hydroxylamine intermediate benzydamine cimetidine clozapine n-deacetyl ketoconazole dmxaa† ethionamide itopride methamphetamine and its hydroxylamine intermediate methimazole nicotine – only the (s)-(−)-nicotine enantiomer olopatadine phenothiazines – 2-(trifluoromethyl) analogs ranitidine sulindac sulfide tamoxifen thiobenzamide xanomeline thiourea chlorpromazine imipramine a † indicates moderate to complete selectivity for fmo3 relative to other fmo isoenzymes. cancer fmo3 gene has been observed progressively downregulated in human papillomavirus-positive neoplastic keratinocytes derived from uterine cervical preneoplastic lesions at different levels of malignancy. for this reason, fmo3 is likely to be associated with tumorigenesis and may be a potential prognostic marker for uterine cervical preneoplastic lesions progression.