Studies on peptides. 64. Synthesis of the tritetracontapeptide corresponding to the entire amino acid sequence of porcine gastric inhibitory polypeptide (GIP).

Abstract

The tritetracontapeptide corresponding to the entire amino acid sequence of porcine gastric inhibitory polypeptide (GIP) was synthesized starting with the C-terminal octadecapeptide, the synthesis of which was previously reported. The hydrogen fluoride procedure was employed to remove all protecting groups employed at the final stage of the synthesis. Trichloroethyloxycarbonylhydrazine was used to prepare alternatively the nonacosapeptide, a cyanogen bromide fragment of GIP, H-(GIP 15-43)-OH. Synthetic GIP suppressed gastric acid secretion stimulated by histamine as well as tetragastrin in Heidenhein pouch dogs. H-(GIP 15-43)-OH exhibited approximately one quarter of the activity of the whole molecule. Association of the insulin release activity in GIP was synthetically confirmed.