Human and Plant Flavin-containing Monooxygenase N-oxygenation of Amines: Detoxication Vs. Bioactivation

Generally, the flavin-containing monooxygenase of mammalian systems has been considered a detoxication enzyme converting nucleophilic heteroatom-containing chemicals into polar, more readily excreted metabolites. The beneficial effects of this process are thought to be participation in the detoxication of foodstuffs and other xenobiotics that might otherwise be bioactivated by other enzyme systems. The physiological role of mammalian FMO is unknown although it has been observed that many heteroatom-containing chemicals in plants are efficiently oxygenated by FMO. Recently, a plant FMO-like enzyme has been characterized and it appears to possess many of the same functional properties of mammalian FMO. The advantage of studying the FMO-like genes and enzymes in Arabidopsis as a model system allows for the investigation of the role of FMO-like enzymes in plant growth and development. The Arabidopsis FMO-like gene product, while resembling the mammalian counterpart in many respects, is quite distinct. However, study of the Arabidopsis FMO-like enzyme may provide considerable insight into the possible role of mammalian FMOs in biogenic amine metabolism.