Purification and properties of dipeptidyl peptidase II from rat kidney

Dipeptidyl peptidase II (EC 3.4.14.2) from rat kidney was purified to a specific activity of 66.2 mumol/min per mg protein by a series of column chromatographic techniques. The purified enzyme was apparently homogeneous as judged by disc gel electrophoresis. Gel filtration on a calibrated column indicated an apparent molecular weight of 130 000 for the native enzyme. Gel electrophoresis of the denatured enzyme in the presence of sodium dodecyl sulfate in a constant acrylamide concentration resulted in the appearance of a single component for which a molecular weight of 64 000 was calculated. The pH optima for dipeptidyl arylamides and for tripeptides were pH 5.5 and 4.5, respectively, and the isoelectric point was 4.8. Substrate specificity studies indicated that the purified enzyme hydrolyzes specifically N-terminal X-alanine or X-proline from their respective arylamides and from tri- or tetrapeptides, but not from pentapeptides.