VAP-1 Human Active Protein

This gene encodes a member of the semicarbazide-sensitive amine oxidase family. Copper amine oxidases catalyze the oxidative conversion of amines to aldehydes in the presence of copper and quinone cofactor. The encoded protein is localized to the cell surface, has adhesive properties as well as monoamine oxidase activity, and may be involved in leukocyte trafficking. Alterations in levels of the encoded protein may be associated with many diseases, including diabetes mellitus. A pseudogene of this gene has been described and is located approximately 9-kb downstream on the same chromosome. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Apr 2013]

Function: Cell adhesion protein that participates in lymphocyte recirculation by mediating the binding of lymphocytes to peripheral lymph node vascular endothelial cells in an L-selectin-independent fashion. Has a monoamine oxidase activity. May play a role in adipogenesis. Ref.2 Ref.9 Ref.10

Catalytic activity: RCH2NH2 + H2O + O2 = RCHO + NH3 + H2O2.

Cofactor: Binds 1 copper ion per subunit.Binds 2 calcium ions per subunit.Contains 1 topaquinone per subunit.

Subunit structure: Homodimer; disulfide-linked. Forms a heterodimer with AOC2. Ref.10 Ref.13

Subcellular location: Membrane; Single-pass type II membrane protein Ref.2.

Tissue specificity: 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. Ref.2 Ref.9

Induction: Up-regulated during in vitro adipocyte differentiation. Ref.9

Post-translational modification: Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue.N- and O-glycosylated. Ref.12 Ref.13

Sequence similarities: Belongs to the copper/topaquinone oxidase family.

Biophysicochemical propertiesKinetic parameters:KM=1.94 mM for 2-phenylethylamine Ref.10KM=0.67 mM for methylamine