Gastrin is a hormonal regulator of various digestive processes and feeding behaviours. It induces gastric secretion, stimulates pancreatic secretion, increases blood circulation and water secretion in the stomach and intestine, and stimulates smooth muscle contraction. Originally found in the gut, it has since been shown to be present in various parts of the nervous system. Like many other active peptides gastrin is synthesized as a larger protein precursor that is enzymatically converted to its mature form. It is found in several molecular forms due to tissue-specific post-translational processing. The biological activity of gastrin is associated with the last five C-terminal residues. One or two positions downstream, there is a conserved sulphated tyrosine residue [, ]. Cionin, a neuropeptide from the protochordate Ciona intestinalis, belongs to this family.
