Catalyzes the oxidative deamination of primary amines to the corresponding aldehydes with the concomitant production of hydrogen peroxide and ammonia. Has a preference for the primary monoamines methylamine and benzylamine. Could also act on 2-phenylethylamine but much less efficiently. 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