InterPro domain: IPR001613

Monoamine oxidases (MAO) A and B are encoded by two genes derived from a common ancestral gene [ 1 ]. The enzymes catalyse the oxidative deamination of biogenic and xenobiotic amines and have important roles in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues [ 2 ]. MAO-A preferentially oxidises biogenic amines such as 5-hydroxytryptamine, norepinephrine and epinephrine. MAO-A deficiency has been linked to Brunner's syndrome, a form of X-linked nondysmorphic mild mental retardation [ 3 ].

The protein contains two similarly-sized subunits, one of which contains covalently-bound flavin adenine dinucleotide (FAD). The FAD binding site lies near the C terminus; at the N terminus are features characteristic of the ADP-binding fold, suggesting that this region is also involved in FAD binding [ 3 ]. The A and B forms of the enzyme share 70% sequence identity; both contain the pentapeptide Ser-Gly-Gly-Cys-Tyr, the cysteine of which binds FAD [ 3 ].

1. Promoter organization and activity of human monoamine oxidase (MAO) A and B genes. J. Neurosci. 12, 4437-46
2. Structural features of human monoamine oxidase A elucidated from cDNA and peptide sequences. J. Neurochem. 51, 1321-4
3. cDNA cloning of human liver monoamine oxidase A and B: molecular basis of differences in enzymatic properties. Proc. Natl. Acad. Sci. U.S.A. 85, 4934-8