Monoamine oxidases (MAOA and B), present in the outer mitochondrial membrane, catalyse the oxidation of biogenic amines, releasing hydrogen peroxide (H2O2). H2O2 produced during the oxidative deamination of these amines appears to be involved in the progress of neurodegenerative disorders such as Parkinson disease, presumably via oxidative damage to the mitochondrial membrane. MAOB (also MAOA but not show here), with FAD as cofactor, can deaminate tyramine (TYR), a naturally-occuring monoamine that can act as a catecholamine releasing agent (Pearce & Roth 1985).