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

Glucagon and a 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 μg/g and 350 μg/g wet tissue, respectively.