Metabolism and inactivation of gastrin releasing peptide by endopeptidase-24.11 in the dog.

The purpose of this investigation was to examine the metabolism and inactivation of gastrin releasing peptide 10 (GRP10) by endopeptidase-24.11 prepared from the stomach wall. GRP10 was metabolized in vitro by gastric endopeptidase-24.11. The metabolites were purified by high-pressure liquid chromatography and identified as (1-8) GRP10 and (9-10) GRP10 by amino acid analysis, indicating hydrolysis of the His8-Leu9 bond. The intravenous administration of GRP10 to conscious dogs stimulated gastrin release, gastric acid secretion, pancreatic protein secretion and pancreatic bicarbonate secretion. Incubation of GRP10 with endopeptidase-24.11 significantly diminished the biological activity of the digests compared to control digests containing heat-inactivated enzyme. This effect was abolished by the enzyme inhibitor phosphoramidon. It is concluded that endopeptidase-24.11 from the stomach metabolizes and inactivates GRP10.