Flavin-containing monooxygenase

The flavin-containing monooxygenase (FMO) protein family consists of a group of enzymes that catalyze chemical reactions via the bound cofactor flavin. These reactions involve oxidation of heteroatoms, particularly nucleophilic atoms such as the nitrogen of amines.

These enzymes metabolise xenobiotics. Using an NADPH cofactor and FAD prosthetic group, these microsomal proteins catalyse the oxygenation of nucleophilic nitrogen, sulphur, phosphorus and selenium atoms in a range of structurally diverse compounds. FMOs have been implicated in the metabolism of a number of pharmaceuticals, pesticides and toxicants. In man, lack of hepatic FMO-catalysed trimethylamine metabolism results in trimethylaminuria (fish odour syndrome). Five mammalian forms of FMO are now known and have been designated FMO1-FMO5.

The best-known such protein is called FMO3 and is mutated in the vast majority of cases of trimethylaminuria, a genetic disease that causes deficiencies in breakdown of trimethylamine and gives the patient a fishy body odor. In yeast, FMO proteins are associated with redox cycling of glutathione to glutathione disulfide, a system that maintains the redox state of the cell and heavily influences the protein folding rates of disulfide bond-containing proteins.

Genes

 * FMO1, FMO2, FMO3, FMO4, FMO5