Flavin dependent monooxygenases FMOs

Monooxygenation of xenobiotics are catalyzed either by the cytochrome P450 (CYP)-dependent monooxygenase system or by flavin-containing monooxygenases (FMO). 

Tertiary amines such as trimethylamine and dimethylamine had long been known to be metabolized to A -oxides by a microsomal amine oxidase that was not dependent on CYP. This enzyme, now known as the microsomal flavin-containing monooxygenase (FMO), is also dependent on NADPH and 02, and has been purified to homogeneity from a number of species. Isolation and characterization of the enzyme from liver and lung samples provided evidence of clearly distinct physicochemical properties and substrate specificities suggesting the presence of at least two different isoforms. Subsequent studies have verified the presence of multiple forms of the enzyme. 

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