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:7792602). Preferentially oxidizes serotonin (PubMed:7792602). 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(+) (R)-adrenaline + H2O + O2 = (R)-3,4-dihydroxymandelaldehyde + H2O2 + methylamine 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 + 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 (By similarity). Belongs to the flavin monoamine oxidase family.