The function of AOC3 (amine oxidase copper containing 3, ENSG00000131471) is as follows. Catalyzes the oxidative deamination of primary amines to the corresponding aldehydes with the concomitant production of hydrogen peroxide and ammonia (PubMed:19588076, PubMed:24304424, PubMed:9653080). Has a preference for the primary monoamines methylamine and benzylamine (PubMed:19588076, PubMed:9653080). Could also act on 2-phenylethylamine but much less efficiently (PubMed:19588076). At endothelial cells surface can also function as a cell adhesion protein that participates in lymphocyte extravasation and recirculation by mediating the binding of lymphocytes to peripheral lymph node vascular endothelial cells in an L-selectin-independent fashion (PubMed:9254657, PubMed:9653080). {ECO:0000269|PubMed:19588076, ECO:0000269|PubMed:24304424, ECO:0000269|PubMed:9254657, ECO:0000269|PubMed:9653080}. [Isoform 2]: Has no semicarbazide-sensitive amine oxidase (SSAO) activity. .