GLYCINE-EXTENDED POSTTRANSLATIONAL PROCESSING INTERMEDIATES OF GASTRIN AND CHOLECYSTOKININ IN THE GUT

Cholecystokinin (CCK) and gastrin are two polypeptide hormones of the gut that share complete structural homology in their carboxyl-terminal pentapeptide. Both peptides are biologically activated from their gly cine-extended precursor forms by a carboxyl-terminal alpha-amidation r eaction. In the present studies we used region specific antisera to ch aracterize the carboxyl-terminally amidated and glycine-extended forms of gastrin and CCK in mammalian intestine. Multiple amidated molecula r forms of gastrin and CCK and their corresponding glycine-extended fo rms were detected throughout the most of the small bowel. Although, we detected substantial amounts of glycine-extended CCK in the proximal rat duodenum, we detected none of the corresponding amidated molecular forms. In contrast, the proximal duodenum of dog and hog contained bo th glycine-extended and amidated CCK. These findings suggest that ther e may be peptide, tissue and species specific differences in expressio n and activity of the peptide alpha-amidating enzyme.