Further characterization of DPP IV-β, a novel cell surface expressed protein with dipeptidyl peptidase activity

Abstract

By using a CD26 negative human lymphoblastoid cell line (C8166), here we describe the characterization of a cell-surface protein which manifests CD26- like dipeptidyl peptidase IV (DPP IV) activity. This protein, referred to as DPP IV-β, shows a higher K(m) value for Gly-Pro-pNA than CD26 (0,31 mM compared to 0,11 mM, respectively). In addition, DPP IV-β was found not to bind 125I-labeled adenosine deaminase (a property of human CD26). Gel filtration experiments using extracts from C8166 and MOLT4 (a CD26 positive human T cell line) cells, revealed that the apparent molecular mass DPP IV- β is 82 kDa, whereas that of CD26 is 110 kDa. In order to conveniently differentiate both activities, a new family of inhibitors, that selectively blocks peptidase activity associated to CD26, has been developed.