Copper amine oxidase that can use putrescine and spermidine as substrates (PubMed:28383668). Involved in putrescine catabolism in peroxisomes in response to salt stress (PubMed:28383668). Regulates arginine-dependent nitric oxide (NO) production, a key signaling molecule regulating a wide range of physiological processes including responses to salt stress, by influencing arginine bioavailability (PubMed:28383668). Modulates primary root growth (PubMed:28383668). an aliphatic amine + H2O + O2 = an aldehyde + H2O2 + NH4(+) Binds 1 copper ion per subunit (By similarity). Can also use zinc ion as cofactor (By similarity). Contains 1 topaquinone per subunit. Amine and polyamine degradation; putrescine degradation. Homodimer. Expressed exclusively in leaves. In young seedlings, first observed in hydathodes and borders of new emerging cotyledons and in leaf primordia (PubMed:31862580). Accumulates in expanding leaves (PubMed:31862580). Induced transiently by auxin (IAA) (PubMed:31862580). Accumulates during dehydration recovery, wounding and treatment with putrescine (Put) and jasmonic acid (MeJA) (PubMed:31862580). Repressed by abscisic acid (ABA) and salicylic acid (SA) (PubMed:31862580). Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue. Decreased nitric oxide (NO) production in seedlings after elicitor treatment with 2,6-dichloroisonicotinic acid (INA) in root tips and salt stress associated with a reduced arginine availability but with a normal nitrate reductase activity in plants (PubMed:28383668). Reduced primary root length (PubMed:28383668). Belongs to the copper/topaquinone oxidase family.