Dipeptidyl peptidase-4

Dipeptidyl peptidase-4 (DPP4), also known as adenosine deaminase complexing protein 2 or CD26 (is_associated_with::cluster of differentiation 26) is a is_associated_with::protein that, in humans, is encoded by the DPP4 is_associated_with::gene. DPP4 is related to attractin, FAP, is_associated_with::DPP8 and is_associated_with::DPP9.

Function
The protein encoded by the DPP4 gene is an antigenic is_associated_with::enzyme expressed on the surface of most cell types and is associated with immune regulation, is_associated_with::signal transduction and is_associated_with::apoptosis. It is an intrinsic membrane is_associated_with::glycoprotein and a serine exopeptidase that cleaves X-proline dipeptides from the is_associated_with::N-terminus of is_associated_with::polypeptides.

It is a rather indiscriminate enzyme for which a diverse range of substrates are known. The substrates of CD26/DPPIV are is_associated_with::proline(or is_associated_with::alanine)-containing peptides and include is_associated_with::growth factors, is_associated_with::chemokines, is_associated_with::neuropeptides, and is_associated_with::vasoactive peptides. DPP4 plays a major role in is_associated_with::glucose metabolism. It is responsible for the degradation of is_associated_with::incretins such as GLP-1. Furthermore, it appears to work as a suppressor in the development of is_associated_with::cancer and is_associated_with::tumours.

DPP-4 also binds the enzyme is_associated_with::adenosine deaminase specifically and with high affinity. The significance of this interaction has yet to be established.

Animal studies
Animal studies suggest its pathogenetic role in development of is_associated_with::fibrosis of various organs, such as liver and kidney.

Clinical significance
CD26/DPPIV plays an important role in tumor biology, and is useful as a marker for various cancers, with its levels either on the cell surface or in the serum increased in some neoplasms and decreased in others.

A new class of is_associated_with::oral hypoglycemics called is_associated_with::dipeptidyl peptidase-4 inhibitors work by inhibiting the action of this enzyme, thereby prolonging incretin effect in vivo.

A new is_associated_with::coronavirus related to SARS, named is_associated_with::Middle East respiratory syndrome coronavirus, has been found to bind to DPP4. DPP4 is found on the surface of cells in the airways (such as the lungs) and kidneys. Scientists may be able to use this to their advantage by blocking the virus's entry into the cell.