Go Back Dipeptidylpeptidase IV (DDP-4), porcine

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DPPIV, dipeptidylpeptidase IV or CD 26, is an integral protein of the plasma membrane of lymphocytes and other mammalian cells, in peptidase family S9 (prolyl oligopeptidase family). The reaction is similiar to that of the unrelated X-Pro dipeptidyl-peptidase of lactococci. DPPIV (serine exopeptidase) is involved in diverse biological processes such as cellular differentiation, T cell activation, and cell-matrix interaction. DPPIV inactivates certain growth factors, chemokines, and neuropeptides by peptide cleavage. It is widely expressed in various normal tissues including normal melanocytes, lung, and prostate epithelial cells. The unprocessed precursor has a relative molecular weight of 88242 Da, whereas the purified enzyme is found to be a dimer, comprising two identical subunits of 110-130 kDa due to the extent of glycosylation. DPPIV releases an N - terminal dipeptide Xaa-Xbb+Xcc from a polypeptide, preferentially when Xbb is Pro, provided Xcc is neither Pro nor hydroxyproline. In addition to synthetic substrates, it also cleaves NYP, GLP1, des-Arg, 1 BK, Casomorphine and the neuropeptide substance P. It has recently been found that transmembrane DPPIV is also capable of cleaving numerous chemokines and cytokines influencing their effect. DPPIV is a surface marker involved in transduction of mitogenic signals in thymocytes and T lymphocytes and is homologous to rat liver gp110. DPPIV is constitutively expressed on many epithelial cell types, and its expression is markedly decreased or completely extinguished in cells derived from melanomas, lung cancer, prostate cancer, and tumorigenic, in vitro transformed epithelial cells. Expression of DPPIV at the RNA level is lost in invasive breast cancer cell lines. Re-expression of DPPIV using tetracycline inducible system, in melanomas and in non small cell lung cancer cells, resulted in profound phenotypic changes that are characteristics of normal cells. DPPIV re-expression led to removal of block in differentiation, acquired dependence on exogenous growth factor for cell survival, and loss of tumorigenicity.