Catalyzes the oxidative deamination of primary and some secondary amines such as neurotransmitters, and exogenous amines including the tertiary amine, neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), with concomitant reduction of oxygen to hydrogen peroxide and participates in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues. Preferentially degrades benzylamine and phenylethylamine. 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(+) benzylamine + H2O + O2 = benzaldehyde + 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(+) 2-phenylethylamine + H2O + O2 = 2-phenylacetaldehyde + H2O2 + NH4(+) H2O + N-acetylputrescine + O2 = 4-acetamidobutanal + 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.