Vascular adhesion protein-1(VAP-1) is a copper amine oxidase with a topaquinone cofactor.VAP-1 is a type II integral membrane protein, but a soluble form of the enzyme is present in human serum, and its level increases in diabetes and some inflammatory liver diseases. VAP-1 catalyzes the oxidative deamination of small primary amines such as methylamine, benzylamine, and aminoacetone in a reaction that produces an aldehyde, ammonia, and H2O2. VAP-1 vascular expression is regulated at sites of inflammation through its release from intracellular granules in which the protein is stored. The adhesive function of VAP-1 has been demonstrated in studies showing that the protein is important for the adherence of certain lymphocyte subtypes to inflamed endothelial tissues. VAP-1 mediated adhesion is involved in the process of leukocyte extravasation, an important feature of inflammatory responses. VAP-1 is considered to be a therapeutic target for diabetes, oxidative stress, and inflammatory diseases.