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. Has semicarbazide-sensitive (SSAO) monoamine oxidase activity. May play a role in adipogenesis. 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. Can heterodimerize with isoform 2 leading to reduced surface expression. Forms a heterodimer with AOC2. Strongly expressed on the high endothelial venules of peripheral lymph nodes and on hepatic endothelia. Also highly expressed in appendix, lung and small intestine. Expressed also in adipose tissue, in bone marrow, colon, heart, kidney, ovary, pancreas, placenta, prostate, skeletal muscle, spleen and testis. Isoform 2 seems to be the predominant transcript in fetal kidneys, fetal cartilage and fetal tonsils. The highest relative expression of isoform 2 occurs in skeletal muscle, heart, pancreas, kidney, and lung. Up-regulated during in vitro adipocyte differentiation. Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue. N- and O-glycosylated. Devoid of the semicarbazide-sensitive amine oxidase (SSAO) activity. Belongs to the copper/topaquinone oxidase family.