Characterization of dipeptidyl peptidase IV from lymphocytes of chronic lymphocytic leukemia of T-type.

Dipeptidyl peptidase IV was enriched about 2000-fold from lymphocytes of chronic lymphocytic leukemia of T-type. The purification procedure involved immunoaffinity chromatography using antibodies raised with highly purified dipeptidyl peptidase IV from human placenta. The lymphocytic peptidase had a subunit Mr of 110,000. Its kinetic properties were similar to those of the placenta enzyme: Two N-terminal dipeptides were cleaved from substance P and from casomorphin, and naphthylamine was released from X-prolynaphthylamides with Km-values of about 0.02 mM. The lymphocytic peptidase was 10-fold less sensitive to zinc inhibition as compared to the placenta enzyme. Isoelectric focussing patterns of dipeptidyl peptidase IV in leukemic lymphocytes and in normal T-lymphocytes were very similar.