Impaired alpha-carboxyamidation of gastrin in vitamin C-deficient guinea pigs.

The biosynthetic activation of many hormonal peptides requires enzymatic alpha-carboxyamidation via glycine-extended intermediate forms. By specific radioimmunochemical measurement on extracts of guinea pig antra, we found that vitamin C deficiency induced a 30-fold increase in glycine-extended (i.e. inactive) gastrins. The results indicate that ascorbic acid is necessary for alpha-carboxyamidation in vivo, and thus, that the biosynthetic activation of hormonal peptides can be modified by simple dietary means.