Isolation and characterization of somatostatin from pigeon pancreas.

Most of the somatostatin-like activity from pigeon pancreas was found to correspond to small species with an apparent molecular weight of 1500--2500. This species was isolated under conditions minimizing intermolecular interactions and protease activities. The isolated product was characterized by two somatostatin radioimmunoassays, a bioassay, endgroup determination, and amino acid analysis. The structure of the isolated compound was determined to be H-Ala-Gly-cyclo-(Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys)-OH. Additionally, small amounts of des-Ala1-somatostatin, a possible degradation product of pancreatic somatostatin, and a large somatostatin-like species with an apparent molecular weight of 11,000--12,500 were detected. It is concluded that the main somatostatin-like polypeptide isolated from pigeon pancreas is identical to the mammalian hypothalamic tetradecapeptide somatostatin.