Isolation and structures of coho salmon (Oncorhynchus kisutch) glucagon and glucagon-like peptide

Glucagon and glucagon-like peptide (GLP) containing 31 amino acids have been isolated from the principal islet of coho salmon (Oncorhynchus kisutch) by gel filtration of acid alcohol extracts followed by HPLC, and the complete amino acid sequence of both peptides has been determined. Salmon glucagon is a simple 29 residue peptide differing at 3 positions when compared to catfish glucagon and at 8 positions when compared to porcine glucagon. Salmon GLP differs at 6 positions when compared with the N-terminal 31 amino acids of the 34 amino acid catfish GLP. Both coho salmon glucagon and GLP cross-react weakly in our mammalian glucagon radioimmunoassay and therefore this technique could not be used to determine tissue content. Glucagon and GLP isolated amounted to 156 micrograms/g and 350 micrograms/g wet tissue, respectively.