Biochem/Physiol Actions | DPPIV has a post-proline dipeptidyl aminopeptidase activity that hydrolyzes N-terminal dipeptides from the unsubstituted N-terminus of peptides with the sequence of X-Pro-Z and X-Ala-Z. The optimum pH is found to be 7.4-8.7. DPPIV is involved in the regulation of several important physiological processes such as immune functions, inflammation, CNS, endocrine functions, bone marrow mobilization, cancer growth, cell adhesion, glucose hemostasis and sepsis/severe infection. Native DPPIV is a ubiquitous type II transmembrane glycoprotein and a serine protease of the S9 prolyl-oligopeptidase family. In vivo, it is synthesized with a signal peptide, which functions as the membrane anchoring domain. There is an 88% sequence homology between the human and porcine kidney enzymes. Both exist as homodimers with a subunit molecular weight of ~30 kDa. The high mannose 100 kDa DPPIV precursor is processed in the Golgi to yield a 124 kDa heavily N-and O-ed mature glycoprotein. It is then sorted to the apical membrane through the concerted action of both N- and O-ed glycans and its association with lipid microdomains. The porcine enzyme contains 18.3% carbohydrates, which the glycan composition is 0.9% fucose, 3.4% mannose, 5.1% galactose, 8.2% glucosamine, and 0.7% sialic acid. DPPIV is highly expressed on endothelial cells, epithelial cells, and lymphocytes. It is also present in plasma in its soluble form. |
