Catalyzes the oxidative deamination of biogenic and xenobiotic amines and has important functions in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues (PubMed:15621520, PubMed:16917825). Preferentially oxidizes serotonin and tyramine (PubMed:15621520, PubMed:16917825). 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 an aliphatic amine + H2O + O2 = an aldehyde + H2O2 + NH4(+) H2O + O2 + serotonin = (5-hydroxyindol-3-yl)acetaldehyde + H2O2 + NH4(+) 2-phenylethylamine + H2O + O2 = 2-phenylacetaldehyde + H2O2 + NH4(+) H2O + O2 + tyramine = (4-hydroxyphenyl)acetaldehyde + H2O2 + NH4(+) dopamine + H2O + O2 = 3,4-dihydroxyphenylacetaldehyde + H2O2 + NH4(+) (R)-adrenaline + H2O + O2 = (R)-3,4-dihydroxymandelaldehyde + H2O2 + methylamine (R)-noradrenaline + H2O + O2 = (R)-3,4-dihydroxymandelaldehyde + H2O2 + NH4(+) H2O + kynuramine + O2 = 3-(2-aminophenyl)-3-oxopropanal + H2O2 + NH4(+) H2O + O2 + tryptamine = H2O2 + indole-3-acetaldehyde + NH4(+) Inhibited by both clorgyline (selective MAOA inhibitor) and deprenyl (selective MAOB inhibitor). Monomer, homo- or heterodimer (containing two subunits of similar size). Each subunit contains a covalently bound flavin. Enzymatically active as monomer (By similarity). Strongest expression in brain and intestine, followed by liver, heart and gill. Little expression in spleen, eye or muscle. In brain, highest activity in noradrenergic and serotonergic cell groups and those of the habenulointerpeduncular pathway; moderate levels in dopaminergic cell clusters. There appears to be only one form of this enzyme in zebrafish, whereas in mammals two forms (MAOA and MAOB) exist. Belongs to the flavin monoamine oxidase family.