Isolation and characterization of reptilian insulin, glucagon, and pancreatic polypeptide: complete amino acid sequence of alligator (Alligator mississippiensis) insulin and pancreatic polypeptide.

The insulin, glucagon, pancreatic polypeptide, and somatostatin contents of acid-alcohol extracts of alligator pancreas have been estimated by heterologous radioimmunoassay, and the insulin, glucagon, and pancreatic polypeptide have been isolated. The amino acid sequences of the insulin and pancreatic polypeptide were determined. The sequence of the insulin A chain is identical to that of chicken insulin A chain, while the B chain exhibits three conservative substitutions when compared to that of the chicken. Pancreatic polypeptide from the alligator is similar in sequence to that of chicken PP, but contains seven substitutions, most of which are conservative and preserve characteristics essential for conformation. The amino acid composition of alligator glucagon is identical to that of duck glucagon.