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

The interaction of dipeptidyl peptidase IV with structurally related protei ns differing in chain length, namely vasostatin I and II and their precurso r protein chromogranin A, was examined using high-performance liquid chroma tography in combination with electrospray mass spectrometry. Suitable analy tical procedures were developed involving the use of reversed-phase high-pe rformance liquid chromatography for purification of the enzymatic degradati on products and a peptide mapping procedure for evaluating the enzymatic de gradation of the large precursor protein chromogranin A. While vasostatin I was found to be a substrate for dipeptidyl peptidase IV, no N-terminal cle avage of Leu-Pro could be noted for chromogranin A. With respect to vasosta tin II, N-terminal degradation was only observed after degradation in the C -terminal domain to proteins containing less than or equal to 78 amino acid s. The specificity of the N-terminal release of Leu-Pro was proved by addit ion of a DPP IV specific inhibitor. Copyright (C) 1999 John Wiley & Sons, L td.