Study of the enzymatic degradation of vasostatin I and II and their precursor chromogranin A by dipeptidyl peptidase IV using high-performance liquid chromatography/electrospray mass spectrometry

The interaction of dipeptidyl peptidase IV with structurally related proteins differing in chain length, namely vasostatin I and II and their precursor protein chromogranin A, was examined using high‐performance liquid chromatography in combination with electrospray mass spectrometry. Suitable analytical procedures were developed involving the use of reversed‐phase high‐performance liquid chromatography for purification of the enzymatic degradation products and a peptide mapping procedure for evaluating the enzymatic degradation of the large precursor protein chromogranin A. While vasostatin I was found to be a substrate for dipeptidyl peptidase IV, no N‐terminal cleavage of Leu–Pro could be noted for chromogranin A. With respect to vasostatin II, N‐terminal degradation was only observed after degradation in the C‐terminal domain to proteins containing ⩽78 amino acids. The specificity of the N‐terminal release of Leu–Pro was proved by addition of a DPP IV specific inhibitor. Copyright © 1999 John Wiley & Sons, Ltd.