Dipeptidyl‐peptidase IV‐β

Abstract

Dipeptidyl peptidase IV-β (DPP IV-β) is a novel protein which shows a peptidase activity similar to the T-cell-activation antigen CD26. To further characterize this DPP IV-β and confirm its cell surface expression, we have developed a purification strategy using the CD26 Ϫ cell line C8166. The purification process includes biotinylation of cell surface proteins before preparation of cell extracts and processing by gel-filtration, ion-exchange and lectin chromatographies. Consistent with the molecular mass of DPP IV-β estimated by gel-filtration chromatography, the final purified fraction, manifesting a typical DPP IV activity, showed a major biotinylated 75Ϫ80-kDa band in SDS/PAGE, thus suggesting the monomeric nature of this enzyme. Kinetic parameters of DPP IV-β and the sensitivity to a new family of irreversible DPP IV inhibitors, were studied in comparison to CD26. Both enzymes followed a Michaelis kinetics with different K m values for Gly-Pro-NH-Np (NH-Np, para-nitroanilide) hydrolysis (0.28 Ϯ 0.05 mM and 0.12Ϯ0.02 mM). More significant differences were observed in the sensitivity to inhibitors, which exerted a much higher activity on CD26 than on DPP IV-β. These differences permitted us to study DPP IV-β expression in CD26-expressing cells, showing the expression of this new enzyme in all lymphoid cells tested, and a rapid enhancement in phytohemagglutinin-stimulated or protein-A-stimulated peripheral blood mononuclear cells. Our results indicate that, although DPP IV-β and CD26 are coexpressed and manifest a typical DPP IV activity, there are distinct features in their catalytic activities that may confer to each enzyme a complementary role in peptide processing.

Glucocorticoid agonistic and antagonistic effects of mifepristone and onapristone on thymocyte subset composition and CD26/dipeptidyl peptidase IV activity in infant male rats

“…This may be due to the lack of correlation between CD26 surface expression and other membrane-bound and cytoplasmic forms of DPP IV-like enzyme activities [48,50,51]. Thus, the cell-surface 75-80 kDa protein referred to as DPP IV-␤ and coexpressed with CD26 [52,53] was characterized in T lymphoblastoid cells. Another DPP IV activity, a membrane-bound 175 kDa protein, was identified as human serum protein attractin [54][55][56].…”

The Therapeutic Potential of Inhibitors of Dipeptidyl Peptidase IV (DPP IV) and Related Proline-Specific Dipeptidyl Aminopeptidases

“…It has been proposed that substrates enter through the β-propeller tunnel and products leave the active site through the side opening [45], but this is still a matter of debate [43]. Another enzyme with DPP IV-like activity is dipeptidyl peptidase IV-β (DPP IV-β) [40]. To date, this enzyme has not been assigned to a family.…”

Dipeptidyl Peptidase IV Inhibition for the Treatment of Type 2 Diabetes

“…In addition to DPP-IV, family members include quiescent cell proline dipeptidase (QPP) (aka DPP7) (12), DPP8 (13), DPP9 (14), fibroblast activation protein (15), attractin (16), and DPP-IV-␤ (17). Except for DPP-IV, the functions of these enzymes are unknown.…”