Has a monoamine oxidase activity with substrate specificity for 2-phenylethylamine and tryptamine. May play a role in adipogenesis. May be a critical modulator of signal transmission in retina. an aliphatic amine + H2O + O2 = an aldehyde + H2O2 + NH4(+) Binds 1 copper ion per subunit. Binds 2 calcium ions per subunit. Contains 1 topaquinone per subunit. Homodimer; disulfide-linked (By similarity). Forms a heterodimer with AOC3, in vitro. Present on the surface of the cells. Either not translocated to the plasma membrane or below detection level. Additional isoforms seem to exist. Expressed in many tissues with much higher expression in retina. Isoform 1 and isoform 2 are expressed in adipose tissue, whereas isoform 1 only seems to be present in thymus, and isoform 2 only in testis. Up-regulated during in vitro adipocyte differentiation. Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue. Belongs to the copper/topaquinone oxidase family.