Prosecretin

Prosecretin is the precursor form of secretin, a peptide hormone produced by enteroendocrine S cells in the mucosa of the duodenum and upper small intestine in humans and other vertebrates. It represents a larger prohormone that contains a signal peptide and the secretin sequence.

Biosynthesis and maturation: The SCT gene encodes the secretin precursor. Translation yields a preproprotein that includes a signal peptide directing entry into the secretory pathway. The signal peptide is removed to form prosecretin, which is stored in secretory granules. Within these granules, prosecretin is proteolytically processed by prohormone convertases at dibasic residues to generate mature secretin, which is released into the bloodstream in response to acidic chyme entering the duodenum.

Function: Secretin acts on target tissues including pancreatic ductal cells via the secretin receptor to stimulate secretion of bicarbonate-rich pancreatic juice, helping neutralize gastric acid. It also influences bile secretion and can modulate gastric motility and enzyme release indirectly. The principal effects are to regulate intestinal pH and optimize digestive processes in the small intestine.

Notes: Nomenclature varies; prosecretin is sometimes used interchangeably with preprosecretin or SCT-derived prohormone. In most physiological contexts, the mature peptide secretin is the active hormone, while prosecretin refers to the precursor form.