Monooxygenases flavin monooxygenase

Flavine monooxygenases. Flavine monooxygenases (FMO) are a family of microsomal flavoproteins that catalyse the oxidation of numerous organic or inorganic compounds, including various strucmrally unrelated xenobiotics, in the presence of NADPH and oxygen. As for cytochrome P450, FMO are involved in detoxication and toxication reactions. 

Scheme 10.17 Reaction cycle of the flavin-dependent squalene monooxygenase. Dashed arrows indicate electron transport.

Flavin-containing Baeyer-Villiger monooxygenases (BVMOs) represent nature s equivalent of conventional peracids or de novo designed metal complexes... 

Kim YM, Ziegler DM. Size limits of thiocarbamides accepted as substrates by human flavin-containing monooxygenase 1. Drug Metab Dispos 2000 28 1003-6. 

All characterized BVMOs contain a flavin cofactor that is crucial for catalysis while NADH or NADPH is needed as electron donor. An interesting observation is the fact that most reported BVMOs are soluble proteins. This is in contrast to many other monooxygenase systems that often are found to be membrane-bound or membrane-associated. In 1997, Willetts concluded from careful inspection of... 

Eppink MHM, SA Boeren, J Vervoort, WJH van Berkel (1997) Purification and properties of 4-hydroxyben-zoate 1-hydroxylase (decarboxylating), a novel flavin adenein dinucleotide-dependent monooxygenase from Candida parapilosis CBS604. J Bacteriol 179 6680-6687. 

The carbamate insecticide aldicarb (Figure 2.13) that exerts its effect by inactivating acetylcholinesterase is metabolized by a flavin monooxygenase from rainbow trout to the sulfoxide, which is a more effective inhibitor (Schlenk and Buhler 1991). 

Schlenk D, DR Buhler (1991) Role of flavin-containing monooxygenase in the in vitro biotransformation of aldicarb in rainbow trout (Oncorhyncus mykiss). Xenobiotica 21 1583-1589. 

The enzyme in Rhodococcus sp. strain IGTS8 that brings about successive oxidation of dibenzothiophene to the sulfoxide and the sulfone is a flavin mononucleotide-dependent monooxygenase that carries out both reactions by sequential incorporation of a single atom of oxygen from Oj (Lei and Tu 1996). 

Gisi MR, L Xun (2003) Characterization of chlorophenol 4-monooxygenase (TftD) and NADH flavin adenine dinucleotide oxidoreductase (TftC) of Burkholderia cepacia ACllOO. J Bacteriol 185 2786-2792. 

Vannelli TA, A Dykman, PR Ortiz de Montellano (2002) The antituberculosis drug ethionamide is activated by a flavin monooxygenase. J Biol Chem 277 12824-12829. 

Yang W, IF Moore, KP Koteva, DC Bareich, DW Hughe, GD Wright (2004) TetX is a flavin-dependent monooxygenase conferring resiatence to tetracycline antibiotics. J Biol Chem 279 52346-52352. 

Oxidative decarboxylation of hydroxybenzoates by the yeast Candida parapsilosis is catalyzed by a flavin monooxygenase that is able to use a range of fluorinated hydroxybenzoates that were examined by F NMR (Eppink et al. 1997). 

Hartmans S, MJ van der Werf, JAM de Bont (1990) Bacterial degradation of styrene involving a novel flavin adenenine dinucleotide-dependent styrene monooxygenase. Appl Environ Microbiol 41 1045-1054. 

Hartmann S, C Hultschig, W Eisenreich, G Fuchs, A Bacher, S Ghisla (1999) NIH shift in flavin-dependent monooxygenation mechanistic studies with 2-aminobenzoyl-CoA monooxygenase/reductase. Proc Natl Acad USA 96 7831-7836. 

Xun L, ER Sandvik (2000) Characterization of 4-hydroxyphenylactate 3-hydroxylase (HpaB) of Escherichia coli as a reduced flavin adenine dinucleotide-utilizing monooxygenase. Appl Environ Microbiol 66 481-486. Zaar A, J Gescher, W Eisenreich, A Bacher, G Fuchs (2004) New enzymes involved in aerobic benzoate metabolism m Azoarcus evansii. Mol Microbiol 54 223-238. 

Becker D, T Schrader, JR Andreesen (1997) Two-component flavin-dependent pyrrole-2-carboxylate monooxygenase from Rhodococcus sp. Eur J Biochem 249 739-747. 

Otto, K., Hofstetter, K., Rothlisherger, M., Witholt, B., Schmid, A. (2004) Biochemical Characterization ofStyAB from Pseudomonas sp strain VLB120 as a Two-Component Flavin-Diffusible Monooxygenase. Journal of Bacteriology, 186(16), 5292-5302. 

Walsh and coworkers oxidized ethyl p-tolyl sulfide on an analytical scale to the S-sulfoxide of 64% enantiomeric purity using a bacterial flavoenzyme cyclohexanone monooxygenase derived from Adnetobacter . Using a flavin adenine dinucleotide containing monooxygenase purified from hog liver microsomes yielded the R-sulfoxide of 90% enantiomeric purity. HPLC on a column containing a 3,5-dinitrobenzoyl-D-phenylglycine chiral stationary phase was used to determine the optical purity of the sulfoxides. 

The assessment of clearance is complicated by the numerous mechanisms by which compounds may be cleared from the body. These mechanisms include oxidative metabolism, most commonly by CYP enzymes, but also in some cases by other enzymes including but not limited to monoamine oxidases (MAO), flavin-containing monooxygenases (FMO), and aldehyde oxidase [45, 46], Non-oxidative metabolism such as conjugation or hydrolysis may be effected by enzymes such as glucuronyl transferases (UGT), glutathione transferases (GST), amidases, esterases, or ketone reductases, as well as other enzymes [47, 48], In addition to metabolic pathways, parent compound may be excreted directly via passive or active transport processes, most commonly into the urine or bile. 

SGAs = second-generation antipsychotics (SGAs) FM03 = flavin-containing monooxygenase TCAs = tricyclic antidepressants Adapted from de Leon et al., 2005b... 

Cashman, J. R. etal. (2001). Population distribution ofhuman flavin-containing monooxygenase form 3 gene polymorphisms. Drug Metab. Dispos., 29, 1629-37. 

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