Catalyzes the oxidative deamination of primary and some secondary amine such as neurotransmitters, with concomitant reduction of oxygen to hydrogen peroxide and has important functions in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues (PubMed:20493079, PubMed:8316221, PubMed:18391214, PubMed:24169519). Preferentially oxidizes serotonin (PubMed:20493079, PubMed:24169519). Also catalyzes the oxidative deamination of kynuramine to 3-(2-aminophenyl)-3-oxopropanal that can spontaneously condense to 4-hydroxyquinoline (By similarity). a secondary aliphatic amine + H2O + O2 = a primary amine + an aldehyde + H2O2 (R)-adrenaline + H2O + O2 = (R)-3,4-dihydroxymandelaldehyde + H2O2 + methylamine an aliphatic amine + H2O + O2 = an aldehyde + H2O2 + NH4(+) dopamine + H2O + O2 = 3,4-dihydroxyphenylacetaldehyde + H2O2 + NH4(+) H2O + O2 + tyramine = (4-hydroxyphenyl)acetaldehyde + H2O2 + NH4(+) (R)-noradrenaline + H2O + O2 = (R)-3,4-dihydroxymandelaldehyde + H2O2 + NH4(+) H2O + O2 + serotonin = (5-hydroxyindol-3-yl)acetaldehyde + H2O2 + NH4(+) H2O + kynuramine + O2 = 3-(2-aminophenyl)-3-oxopropanal + H2O2 + NH4(+) H2O + O2 + tryptamine = H2O2 + indole-3-acetaldehyde + NH4(+) 2-phenylethylamine + H2O + O2 = 2-phenylacetaldehyde + H2O2 + NH4(+) Monomer, homo- or heterodimer (containing two subunits of similar size). Each subunit contains a covalently bound flavin. Enzymatically active as monomer. Heart, liver, duodenum, blood vessels and kidney. A polymorphism 1.2 kb upstream of the MAOA coding sequences consists of a 30-bp repeated sequence present in 3, 3.5, 4, or 5 copies. The polymorphism affect transcriptional activity of the MAOA gene promoter. Alleles with 3.5 or 4 copies of the repeat sequence are transcribed 2 to 10 times more efficiently than those with 3 or 5 copies of the repeat. The disease is caused by variants affecting the gene represented in this entry. Belongs to the flavin monoamine oxidase family. Monoamine oxidase entry Approaching happiness - Issue 172 of August 2015