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Gene Review

Fmo1  -  flavin containing monooxygenase 1

Rattus norvegicus

Synonyms: Dimethylaniline oxidase 1, FMO 1, Fmo-1, Hepatic flavin-containing monooxygenase 1
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Disease relevance of Fmo1

  • These results suggest that NO acts directly in a cGMP-independent mechanism by decreasing the half-life of FMO1 mRNA, thereby inducing impairment of FMO-related functions in endotoxemia [1].
  • This study demonstrates alteration of FMO- and CYP-mediated drug metabolism in vitro by dietary I3C or DIM and suggests the potential for altered toxicity of tamoxifen and nicotine in vivo [2].
  • Methimazole is a compound administered to humans for the treatment of hyperthyroidism and is used experimentally as a model substrate for the flavin-containing monooxygenase (FMO) system [3].

High impact information on Fmo1

  • Flavin-containing monooxygenase alternate substrates, N,N-dimethylaniline, n-octylamine, and methimazole inhibited the S-oxidase activities [4].
  • The levels of another microsomal enzyme, flavin-containing monooxygenase, were also measured and found to be regulated by testosterone, but the ontogenic profiles and the effects of gonadectomy and hormone replacement indicated clear differences in its regulation when compared to the other male-specific enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)[5]
  • In contrast to these NO-mediated in vivo suppressive effects on the mRNA and enzyme contents of FMO1 as well as the FMO activity, the NO generated in vitro from sodium nitroprusside did not inhibit the FMO activities present in microsomes of rat and rabbit liver as well as those present in rabbit kidney and lung [6].
  • Attendant with the reduction of plasma nitrite/nitrate concentration by single and repeated doses of NOS inhibitors, activity and content of FMO1 in liver microsomes isolated from these NOS inhibitor cotreated rats were restored partially (in single-dose inhibitors) or completely (in repeat doses) [6].
  • When this overproduction of NO in the LPS-treated rats was inhibited in vivo by a single or repeat doses of either a general NOS inhibitor N(G)-nitro-L-arginine or a specific iNOS inhibitor aminoguanidine, the FMO1 mRNA levels were not severely depressed (70-85% of the control level) [6].

Biological context of Fmo1


Anatomical context of Fmo1


Associations of Fmo1 with chemical compounds

  • Flavin-containing monooxygenase activity in hepatocytes and microsomes: in vitro characterization and in vivo scaling of benzydamine clearance [14].
  • Because cDNA-expressed rabbit FMO3 and FMO1 were previously shown to preferentially catalyze methionine and S-benzyl-L-cysteine (SBC) sulfoxidations, respectively, these substrates were used to isolate two distinct S-oxidase activities from the same rat liver microsomal preparation [15].
  • To examine a molecular basis for the influence of total parenteral nutrition +/- choline on monooxygenase regulation, hepatic microsomal activity of the FMO and CYP2E1 was examined [16].
  • Although the data did not reach statistical significance, selective immunoblot studies using hepatic microsomes from rats treated with total parenteral nutrition + choline showed that compared with controls, FMO1 protein was decreased 1.4-fold and FMO3 increased 1.3-fold, respectively [16].
  • The N-oxygenation of trimethylamine was used as an in vivo selective functional marker for FMO [16].

Other interactions of Fmo1


Analytical, diagnostic and therapeutic context of Fmo1


  1. Hepatic flavin-containing monooxygenase activity attenuated by cGMP-independent nitric oxide-mediated mRNA destabilization. Ryu, S.D., Kang, J.H., Yi, H.G., Nahm, C.H., Park, C.S. Biochem. Biophys. Res. Commun. (2004) [Pubmed]
  2. Concurrent flavin-containing monooxygenase down-regulation and cytochrome P-450 induction by dietary indoles in rat: implications for drug-drug interaction. Katchamart, S., Stresser, D.M., Dehal, S.S., Kupfer, D., Williams, D.E. Drug Metab. Dispos. (2000) [Pubmed]
  3. Olfactory toxicity of methimazole: dose-response and structure-activity studies and characterization of flavin-containing monooxygenase activity in the Long-Evans rat olfactory mucosa. Genter, M.B., Deamer, N.J., Blake, B.L., Wesley, D.S., Levi, P.E. Toxicologic pathology. (1995) [Pubmed]
  4. Cysteine conjugate S-oxidase. Characterization of a novel enzymatic activity in rat hepatic and renal microsomes. Sausen, P.J., Elfarra, A.A. J. Biol. Chem. (1990) [Pubmed]
  5. Hormonal regulation of rat liver microsomal enzymes. Role of gonadal steroids in programming, maintenance, and suppression of delta 4-steroid 5 alpha-reductase, flavin-containing monooxygenase, and sex-specific cytochromes P-450. Dannan, G.A., Guengerich, F.P., Waxman, D.J. J. Biol. Chem. (1986) [Pubmed]
  6. Suppression of flavin-containing monooxygenase by overproduced nitric oxide in rat liver. Park, C.S., Baek, H.M., Chung, W.G., Lee, K.H., Ryu, S.D., Cha, Y.N. Mol. Pharmacol. (1999) [Pubmed]
  7. Rat liver flavin-containing monooxygenase (FMO): cDNA cloning and expression in yeast. Itoh, K., Kimura, T., Yokoi, T., Itoh, S., Kamataki, T. Biochim. Biophys. Acta (1993) [Pubmed]
  8. Cloning, sequencing, and tissue-dependent expression of flavin-containing monooxygenase (FMO) 1 and FMO3 in the dog. Lattard, V., Longin-Sauvageon, C., Lachuer, J., Delatour, P., Benoit, E. Drug Metab. Dispos. (2002) [Pubmed]
  9. Hormonal regulation of microsomal flavin-containing monooxygenase: tissue-dependent expression and substrate specificity. Lemoine, A., Williams, D.E., Cresteil, T., Leroux, J.P. Mol. Pharmacol. (1991) [Pubmed]
  10. Age-related susceptibility to 3,3'-iminodipropionitrile-induced olfactory mucosal damage. Genter, M.B., Ali, S.F. Neurobiol. Aging (1998) [Pubmed]
  11. Microsomal flavin-containing monooxygenase activity in rat corpus striatum. Duffel, M.W., Gillespie, S.G. J. Neurochem. (1984) [Pubmed]
  12. Hormonal regulation of microsomal flavin-containing monooxygenase activity by sex steroids and growth hormone in co-cultured adult male rat hepatocytes. Coecke, S., Debast, G., Phillips, I.R., Vercruysse, A., Shephard, E.A., Rogiers, V. Biochem. Pharmacol. (1998) [Pubmed]
  13. Bioactivation mechanism of S-(3-oxopropyl)-N-acetyl-L-cysteine, the mercapturic acid of acrolein. Hashmi, M., Vamvakas, S., Anders, M.W. Chem. Res. Toxicol. (1992) [Pubmed]
  14. Flavin-containing monooxygenase activity in hepatocytes and microsomes: in vitro characterization and in vivo scaling of benzydamine clearance. Fisher, M.B., Yoon, K., Vaughn, M.L., Strelevitz, T.J., Foti, R.S. Drug Metab. Dispos. (2002) [Pubmed]
  15. Characterization of the methionine S-oxidase activity of rat liver and kidney microsomes: immunochemical and kinetic evidence for FMO3 being the major catalyst. Krause, R.J., Ripp, S.L., Sausen, P.J., Overby, L.H., Philpot, R.M., Elfarra, A.A. Arch. Biochem. Biophys. (1996) [Pubmed]
  16. Effect of total parenteral nutrition and choline on hepatic flavin-containing and cytochrome P-450 monooxygenase activity in rats. Cashman, J.R., Lattard, V., Lin, J. Drug Metab. Dispos. (2004) [Pubmed]
  17. Physiological factors affecting the expression of FMO1 and FMO3 in the rat liver and kidney. Lattard, V., Lachuer, J., Buronfosse, T., Garnier, F., Benoit, E. Biochem. Pharmacol. (2002) [Pubmed]
  18. Involvement of reactive oxygen species in the microsomal S-oxidation of thiobenzamide. Younes, M. Experientia (1985) [Pubmed]
  19. Activation of 3,3'-dichlorobenzidine in rat liver microsomes to mutagens: involvement of cytochrome P-450d. Iba, M.M., Thomas, P.E. Carcinogenesis (1988) [Pubmed]
  20. Activities of cytosolic and microsomal drug oxidases of rat hepatocytes in primary culture. Sherratt, A.J., Damani, L.A. Drug Metab. Dispos. (1989) [Pubmed]
  21. Stereoselective S-oxidation of flosequinan sulfide by rat hepatic flavin-containing monooxygenase 1A1 expressed in yeast. Kashiyama, E., Yokoi, T., Itoh, K., Itoh, S., Odomi, M., Kamataki, T. Biochem. Pharmacol. (1994) [Pubmed]
  22. Further characterization of rat brain flavin-containing monooxygenase. Metabolism of imipramine to its N-oxide. Bhagwat, S.V., Bhamre, S., Boyd, M.R., Ravindranath, V. Biochem. Pharmacol. (1996) [Pubmed]
  23. An assay of flavin-containing monooxygenase activity with benzydamine N-oxidation. Kawaji, A., Ohara, K., Takabatake, E. Anal. Biochem. (1993) [Pubmed]
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