Flavin Containing Monooxygenase 5 (FMO5)

Metabolic N-oxidation of the diet-derived amino-trimethylamine (TMA) is mediated by flavin-containing monooxygenase and is subject to an inherited FMO3 polymorphism in man resulting in a small subpopulation with reduced TMA N-oxidation capacity resulting in fish odor syndrome Trimethylaminuria. Three forms of the enzyme, FMO1 found in fetal liver, FMO2 found in adult liver, and FMO3 are encoded by genes clustered in the 1q23-q25 region. The predicted 533-amino acid human protein shares 85% and 87% sequence identity with rabbit and guinea pig FMO5, respectively. Northern blot analysis revealed that the human FMO5 gene is expressed as 2.6- and 3.8-kb mRNAs in liver. The FMO5 protein had an apparent molecular mass of 60 kD on Western blots of adult and neonatal human liver.