H2O + histamine + O2 = H2O2 + imidazole-4-acetaldehyde + NH4(+) Binds 1 copper ion per subunit (By similarity). Can also use zinc ion as cofactor (By similarity). Contains 1 topaquinone per subunit. Binds 1 Mn(2+) ion per subunit. Homodimer. By N-butylamine. Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue. Belongs to the copper/topaquinone oxidase family.