Description
Dipeptidyl Peptidase IV (DPPIV)/CD26, is a highly conserved type I I integral membrane protein associated with immune regulation, signal transduction and apoptosis, and is constitutively expressed on a wide variety of epithelial, endothelial, and lymphoid cell types. DPPIV is a serine exopeptidase catalyzing the cleavage of N-terminal Xaa-Pro dipeptides from peptides, and its substrates include growth factors, chemokines, neuropeptides, and vasoactive peptides. As a T cell-activating molecule (THAM), DPPIV plays important roles in the T cell-mediated immune responses through the regulation of differentiation and growth of T lymphocytes, and also probably acts as a cofactor for entry of HIV in CD4+ cells. Furthermore, DPPIV appears to work as a suppressor in the progression of certain tumors, and also exerts actions in glucose metabolism via interaction with glucagons. DPPIV also binds the enzyme adenosine deaminase specifically with high affinity. Elevated expression of DPPIV is associated with autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis. The levels of DPPIV soluble form in serum and body fluids have clinical significance in patients with cancer, liver, kidney diseases and depression