Flavin-containing monooxygenase 3

FMO3
Identifiers
Aliases	FMO3, trimethylamine monooxygenase, flavin-containing monooxygenase 3, Dimethylaniline monooxygenase [N-oxide-forming] 3, FMOII, TMAU, dJ127D3.1, flavin containing monooxygenase 3
External IDs	OMIM: 136132 MGI: 1100496 HomoloGene: 128199 GeneCards: FMO3
EC number	1.14.13.148
Gene ontology Molecular function • trimethylamine monooxygenase activity • oxidoreductase activity • N,N-dimethylaniline monooxygenase activity • NADP binding • flavin adenine dinucleotide binding • monooxygenase activity Cellular component • integral component of membrane • organelle membrane • endoplasmic reticulum membrane • intracellular membrane-bounded organelle • endoplasmic reticulum • membrane Biological process • xenobiotic metabolic process • oxidation-reduction process Sources:Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	2328	14262
Ensembl	ENSG00000007933	ENSMUSG00000026691
UniProt	P31513	P97501
RefSeq (mRNA)	NM_001002294 NM_006894 NM_001319173 NM_001319174	NM_008030
RefSeq (protein)	NP_001002294.1 NP_008825.4 NP_001306102.1 NP_001306103.1	NP_032056.1
Location (UCSC)	Chr 1: 171.09 – 171.12 Mb	Chr 1: 162.95 – 162.98 Mb
PubMed search	[1]	[2]
Wikidata

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Flavin-containing monooxygenase 3 (FMO3), also known as dimethylaniline monooxygenase [N-oxide-forming] 3 and trimethylamine monooxygenase, is a flavoprotein enzyme (EC 1.14.13.148) that in humans is encoded by the FMO3 gene.^[3][4][5][6] This enzyme catalyzes the following chemical reaction:^[6]

N,N,N-trimethylamine + NADPH + H⁺ + O₂ $\rightleftharpoons$ N,N,N-trimethylamine N-oxide + NADP⁺ + H₂O

FMO3 is the main flavin-containing monooxygenase isoenzyme that is expressed in the liver of adult humans.^[6][7][8] The human FMO3 enzyme catalyzes several types of reactions, including: the N-oxygenation of primary, secondary, and tertiary amines;^[7][9] the S-oxygenation of nucleophilic sulfur-containing compounds;^[7][9] and the 6-methylhydroxylation of DMXAA.^[7][10]

FMO3 is the primary enzyme in humans which catalyzes the N-oxidation of trimethylamine into trimethylamine N-oxide;^[6][8] FMO1 also N-oxygenates trimethylamine, but to a much lesser extent than FMO3.^[11][12] Genetic deficiencies of the FMO3 enzyme cause primary trimethylaminuria, also known as "fish odor syndrome".^[6][13] FMO3 is also involved in the metabolism of many xenobiotics (i.e., exogenous compounds which are not normally present in the body),^[7][8] such as the oxidative deamination of amphetamine.^[7][14][15]

Ligands

List of human FMO3 substrates, inhibitors, inducers, and activators

FMO3 substrates	FMO3 inhibitors	FMO3 inducers	FMO3 activators
Endogenous biomolecules Epinephrine[16] Norepinephrine[16] Phenethylamine^†[7][16] Trimethylamine^†[7][8][16] Tyramine[6][7][16] Notable exogenous xenobiotics Amphetamine^† and its hydroxylamine intermediate[7][15] Benzydamine[6][7] Cimetidine[8][9] Clozapine[7][8] N-Deacetyl ketoconazole[7] DMXAA^†[7][10] Ethionamide[6][7] Itopride[7][8] Methamphetamine and its hydroxylamine intermediate[7][15] Methimazole[6][8] Nicotine – only the (S)-(−)-nicotine enantiomer[7][9] Olopatadine[7] Phenothiazines – 2-(Trifluoromethyl) analogs[7] Ranitidine[7][9] Sulindac sulfide[6][7] Tamoxifen[7][8] Thiobenzamide[7] Xanomeline[7]	Thiourea[6]		Chlorpromazine[6] Imipramine[6]
A ^† indicates moderate to complete selectivity for FMO3 relative to other FMO isoenzymes.

See also

• Flavin-containing monooxygenase
• Trimethylaminuria

References

1. "Human PubMed Reference:".
2. "Mouse PubMed Reference:".
3. Shephard EA, Dolphin CT, Fox MF, Povey S, Smith R, Phillips IR (June 1993). "Localization of genes encoding three distinct flavin-containing monooxygenases to human chromosome 1q". Genomics. 16 (1): 85–9. doi:10.1006/geno.1993.1144. PMID 8486388.
4. Dolphin CT, Riley JH, Smith RL, Shephard EA, Phillips IR (February 1998). "Structural organization of the human flavin-containing monooxygenase 3 gene (FMO3), the favored candidate for fish-odor syndrome, determined directly from genomic DNA". Genomics. 46 (2): 260–7. doi:10.1006/geno.1997.5031. PMID 9417913.
5. "Entrez Gene: FMO3 flavin containing monooxygenase 3".
6. "Trimethylamine monooxygenase (Homo sapiens)". BRENDA. Technische Universität Braunschweig. July 2016. Retrieved 18 September 2016. trimethylaminuria (fish-odor syndrome) is associated with defective hepatic N-oxidation of dietary-derived trimethylamine catalyzed by flavin-containing monooxygenase ... FMO3 deficiency results in trimethylaminuria or the fish-like odour syndrome ... isozyme FMO3 regulates the conversion of N,N,N-trimethylamine into its N-oxide and hence controls the release of volatile N,N,N-trimethylamine from the individual
7. Krueger SK, Williams DE (June 2005). "Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism". Pharmacol. Ther. 106 (3): 357–387. doi:10.1016/j.pharmthera.2005.01.001. PMC 1828602. PMID 15922018. A second precaution with respect to predicting FMO enzyme substrate specificity is that factors other than size and charge must play a role, but these parameters are not well understood. An example is the high selectivity observed with human FMO3, compared to the other FMO enzymes, in the N-oxygenation of the important constitutive substrate trimethylamine (Lang et al., 1998). ... The most efficient human FMO in phenethylamine N-oxygenation is FMO3, the major FMO present in adult human liver; the Km is between 90 and 200 μM (Lin & Cashman, 1997b). ... Of particular significance for this review is that individuals homozygous for certain FMO3 allelic variants (e.g., null variants) also demonstrate impaired metabolism toward other FMO substrates including ranitidine, nicotine, thio-benzamide, and phenothiazine derivatives (Table 4; Cashman et al., 1995, 2000; Kang et al., 2000; Cashman, 2002; Park et al., 2002; Lattard et al., 2003a, 2003b). ... The metabolic activation of ethionamide by the bacterial FMO is the same as the mammalian FMO activation of thiobenzamide to produce hepatotoxic sulfinic and sulfinic acid metabolites. Not surprisingly, Dr. Ortiz de Montellano’s laboratory and our own have found ethionamide to be a substrate for human FMO1, FMO2, and FMO3 (unpublished observations).
   Table 5: N-containing drugs and xenobiotics oxygenated by FMO
   Table 6: S-containing drugs and xenobiotics oxygenated by FMO
   Table 7: FMO activities not involving S- or N-oxygenation
8. Hisamuddin IM, Yang VW (June 2007). "Genetic polymorphisms of human flavin-containing monooxygenase 3: implications for drug metabolism and clinical perspectives". Pharmacogenomics. 8 (6): 635–643. doi:10.2217/14622416.8.6.635. PMC 2213907. PMID 17559352. Other drug substrates have been used for both in vitro and in vivo analyses. ... FMO3 is the most abundantly expressed FMO in the adult human liver [12]. Its structure and function and the implications of its polymorphisms have been widely studied [8,12,13]. This enzyme has a wide substrate specificity, including the dietary-derived tertiary amines trimethylamine, tyramine and nicotine; commonly used drugs including cimetidine, ranitidine, clozapine, methimazole, itopride, ketoconazole, tamoxifen and sulindac sulfide; and agrichemicals, such as organophosphates and carbamates [14–22].
9. Cashman JR (September 2000). "Human flavin-containing monooxygenase: substrate specificity and role in drug metabolism". Curr. Drug Metab. 1 (2): 181–191. PMID 11465082. Human FMO3 N-oxygenates primary, secondary and tertiary amines whereas human FMO1 is only highly efficient at N-oxygenating tertiary amines. Both human FMO1 and FMO3 S-oxygenate a number of nucleophilic sulfur-containing substrates and in some cases, does so with great stereoselectivity. ... For amines with smaller aromatic substituents such as phenethylamines, often these compounds are efficiently N-oxygenated by human FMO3. ... (S)-Nicotine N-1'-oxide formation can also be used as a highly stereoselective probe of human FMO3 function for adult humans that smoke cigarettes. Finally, cimetidine S-oxygenation or ranitidine N-oxidation can also be used as a functional probe of human FMO3. With the recent observation of human FMO3 genetic polymorphism and poor metabolism phenotype in certain human populations, variant human FMO3 may contribute to adverse drug reactions or exaggerated clinical response to certain medications.
10. Zhou S, Kestell P, Paxton JW (July 2002). "6-methylhydroxylation of the anti-cancer agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) by flavin-containing monooxygenase 3". Eur J Drug Metab Pharmacokinet. 27 (3): 179–183. PMID 12365199. Only FMO3 formed 6-OH-MXAA at a similar rate to that in cDNA-expressed cytochromes P-450 (CYP)1A2. The results of this study indicate that human FMO3 has the capacity to form 6-OH-MXAA, but plays a lesser important role for this reaction than CYP1A2 that has been demonstrated to catalyse 6-OH-MXAA formation.
11. Tang WH, Hazen SL (October 2014). "The contributory role of gut microbiota in cardiovascular disease". J. Clin. Invest. 124 (10): 4204–4211. doi:10.1172/JCI72331. PMC 4215189. PMID 25271725. In recent studies each of the FMO family members were cloned and expressed, to determine which possessed synthetic capacity to use TMA as a substrate to generate TMAO. FMO1, FMO2, and FMO3 were all capable of forming TMAO, though the specific activity of FMO3 was at least 10-fold higher than that the other FMOs (54). Further, FMO3 overexpression in mice significantly increased plasma TMAO levels, while silencing FMO3 decreased TMAO levels (54). In both humans and mice, hepatic FMO3 expression was observed to be reduced in males compared with females (25, 54) and could be induced by dietary bile acids through a mechanism that involves FXR (54).
12. Bennett BJ, de Aguiar Vallim TQ, Wang Z, Shih DM, Meng Y, Gregory J, Allayee H, Lee R, Graham M, Crooke R, Edwards PA, Hazen SL, Lusis AJ (2013). "Trimethylamine-N-oxide, a metabolite associated with atherosclerosis, exhibits complex genetic and dietary regulation". Cell Metab. 17 (1): 49–60. doi:10.1016/j.cmet.2012.12.011. PMC 3771112. PMID 23312283. Circulating trimethylamine-N-oxide (TMAO) levels are strongly associated with atherosclerosis. We now examine genetic, dietary, and hormonal factors regulating TMAO levels. We demonstrate that two flavin mono-oxygenase family members, FMO1 and FMO3, oxidize trimethylamine (TMA), derived from gut flora metabolism of choline, to TMAO. Further, we show that FMO3 exhibits 10-fold higher specific activity than FMO1.
13. Dolphin CT, Janmohamed A, Smith RL, Shephard EA, Phillips IR (1997). "Missense mutation in flavin-containing mono-oxygenase 3 gene, FMO3, underlies fish-odour syndrome". Nat. Genet. 17 (4): 491–4. doi:10.1038/ng1297-491. PMID 9398858.
14. Glennon RA (2013). "Phenylisopropylamine stimulants: amphetamine-related agents". In Lemke TL, Williams DA, Roche VF, Zito W. Foye's principles of medicinal chemistry (7th ed.). Philadelphia, USA: Wolters Kluwer Health/Lippincott Williams & Wilkins. pp. 646–648. ISBN 9781609133450. Retrieved 11 September 2015. The simplest unsubstituted phenylisopropylamine, 1-phenyl-2-aminopropane, or amphetamine, serves as a common structural template for hallucinogens and psychostimulants. Amphetamine produces central stimulant, anorectic, and sympathomimetic actions, and it is the prototype member of this class (39). ... The phase 1 metabolism of amphetamine analogs is catalyzed by two systems: cytochrome P450 and flavin monooxygenase.
15. Cashman JR, Xiong YN, Xu L, Janowsky A (March 1999). "N-oxygenation of amphetamine and methamphetamine by the human flavin-containing monooxygenase (form 3): role in bioactivation and detoxication". J. Pharmacol. Exp. Ther. 288 (3): 1251–1260. PMID 10027866.
16. Robinson-Cohen C, Newitt R, Shen DD, Rettie AE, Kestenbaum BR, Himmelfarb J, Yeung CK (August 2016). "Association of FMO3 Variants and Trimethylamine N-Oxide Concentration, Disease Progression, and Mortality in CKD Patients". PLoS ONE. 11 (8): e0161074. doi:10.1371/journal.pone.0161074. PMC 4981377. PMID 27513517. TMAO is generated from trimethylamine (TMA) via metabolism by hepatic flavin-containing monooxygenase isoform 3 (FMO3). ... FMO3 catalyzes the oxidation of catecholamine or catecholamine-releasing vasopressors, including tyramine, phenylethylamine, adrenaline, and noradrenaline [32, 33].

External links

• Trimethylamine monooxygenase at the US National Library of Medicine Medical Subject Headings (MeSH)
• Primary Trimethylaminuria (FMO3 Deficiency) – NCBI bookshelf GeneReviews entry

Further reading

• Cashman JR, Park SB, Berkman CE, Cashman LE (1995). "Role of hepatic flavin-containing monooxygenase 3 in drug and chemical metabolism in adult humans.". Chem. Biol. Interact. 96 (1): 33–46. doi:10.1016/0009-2797(94)03581-R. PMID 7720103.
• Cashman JR (2004). "The implications of polymorphisms in mammalian flavin-containing monooxygenases in drug discovery and development.". Drug Discov. Today. 9 (13): 574–81. doi:10.1016/S1359-6446(04)03136-8. PMID 15203093.
• Zhou J, Shephard EA (2006). "Mutation, polymorphism and perspectives for the future of human flavin-containing monooxygenase 3.". Mutat. Res. 612 (3): 165–71. doi:10.1016/j.mrrev.2005.09.001. PMID 16481213.
• Lomri N, Gu Q, Cashman JR (1992). "Molecular cloning of the flavin-containing monooxygenase (form II) cDNA from adult human liver.". Proc. Natl. Acad. Sci. U.S.A. 89 (5): 1685–9. doi:10.1073/pnas.89.5.1685. PMC 48517. PMID 1542660.
• Humbert JA, Hammond KB, Hathaway WE (1970). "Trimethylaminuria: the fish-odour syndrome.". Lancet. 2 (7676): 770–1. doi:10.1016/S0140-6736(70)90241-2. PMID 4195988.
• Higgins T, Chaykin S, Hammond KB, Humbert JR (1972). "Trimethylamine N-oxide synthesis: a human variant.". Biochemical medicine. 6 (4): 392–6. doi:10.1016/0006-2944(72)90025-7. PMID 5048998.
• Lomri N, Gu Q, Cashman JR (1995). "Molecular cloning of the flavin-containing monooxygenase (form II) cDNA from adult human liver.". Proc. Natl. Acad. Sci. U.S.A. 92 (21): 9910. doi:10.1073/pnas.92.21.9910. PMC 40912. PMID 7568243.
• Bhamre S, Bhagwat SV, Shankar SK, et al. (1995). "Flavin-containing monooxygenase mediated metabolism of psychoactive drugs by human brain microsomes.". Brain Res. 672 (1–2): 276–80. doi:10.1016/0006-8993(94)01135-5. PMID 7749747.
• Cashman JR, Park SB, Yang ZC, et al. (1993). "Chemical, enzymatic, and human enantioselective S-oxygenation of cimetidine". Drug Metab. Dispos. 21 (4): 587–97. PMID 8104117.
• Park SB, Jacob P, Benowitz NL, Cashman JR (1994). "Stereoselective metabolism of (S)-(−)-nicotine in humans: formation of trans-(S)-(−)-nicotine N-1'-oxide". Chem. Res. Toxicol. 6 (6): 880–8. doi:10.1021/tx00036a019. PMID 8117928.
• Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID 8125298.
• Dolphin CT, Cullingford TE, Shephard EA, et al. (1996). "Differential developmental and tissue-specific regulation of expression of the genes encoding three members of the flavin-containing monooxygenase family of man, FMO1, FMO3 and FM04". Eur. J. Biochem. 235 (3): 683–9. doi:10.1111/j.1432-1033.1996.00683.x. PMID 8654418.
• Chung WG, Cha YN (1997). "Oxidation of caffeine to theobromine and theophylline is catalyzed primarily by flavin-containing monooxygenase in liver microsomes". Biochem. Biophys. Res. Commun. 235 (3): 685–8. doi:10.1006/bbrc.1997.6866. PMID 9207220.
• Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149.
• Treacy EP, Akerman BR, Chow LM, et al. (1998). "Mutations of the flavin-containing monooxygenase gene (FMO3) cause trimethylaminuria, a defect in detoxication". Hum. Mol. Genet. 7 (5): 839–45. doi:10.1093/hmg/7.5.839. PMID 9536088.
• Akerman BR, Forrest S, Chow L, et al. (1999). "Two novel mutations of the FMO3 gene in a proband with trimethylaminuria". Hum. Mutat. 13 (5): 376–9. doi:10.1002/(SICI)1098-1004(1999)13:5<376::AID-HUMU5>3.0.CO;2-A. PMID 10338091.