Identification and characterization of variant forms of the gastrin-releasing peptide (GRP)

Porcine intestinal gastrin-releasing peptide (GRP) has been demonstrated to be structurally identical to the previously characterized gastric GRP. Ion-exchange and high-performance liquid chromatography of porcine intestinal extracts have identified two variant GRP forms. Studies on one of these variant forms suggest that a beta-aspartyl shift has occurred in the Asn-His structure of GRP; such a modification in an Asn-His structure occurring in a natural peptide or protein has not been previously reported. This variant GRP, although retaining bioactivity, appears to have reduced potency in elevating canine plasma gastrin levels.