Progastrin and its glycine-extended posttranslational processing intermediates in human gastrointestinal tissues.

We examined the posttranslational modification of gastrin in human gastrointestinal and Zollinger-Ellison tumor tissues using antibodies specific for progastrin and its glycine-extended processing intermediates. Gel filtration of antral and duodenal extracts on Sephadex G-50 revealed multiple molecular forms of immunoreactive glycine-extended processing intermediates corresponding to known molecular forms of gastrin and cholecystokinin. Immunoaffinity chromatography studies of antral mucosal and gastrinoma extracts identified a molecular form of glycine-extended processing intermediates that was characterized by an amino terminus identical to that of gastrin heptadecapeptide. Large differences in the relative contents of precursors and products of gastrin synthesis were found in gastrinoma tissue as compared to gastrointestinal mucosal extracts. These studies suggest the potential importance of glycine-extended peptides as intermediates in the posttranslational processing of gastrin and cholecystokinin in humans and indicate that gastrin processing mechanisms may be altered in Zollinger-Ellison tumors.