Isolation of alligator gar (Lepisosteus spatula) glucagon, oxyntomodulin, and glucagon-like peptide: amino acid sequences of oxyntomodulin and glucagon-like peptide.

Oxyntomodulin, glucagon, and a glucagon-like peptide (GLP) have been isolated from the endocrine pancreas of the alligator gar (Lepisosteus spatula), a ganoid fish. The three peptides were isolated by gel filtration and HPLC and were identified by size, composition, and glucagon-like immunoreactivity. The amino acid sequences of the oxyntomodulin and GLP were determined. The oxyntomodulin contains 36 amino acid residues and its sequence is H S Q G T F T N D Y S K Y L D T R R A Q D F V Q W L M S T K R S G G I T. The composition of the glucagon is identical to the N-terminal 29 residues of the gar oxyntomodulin. The single form of GLP found contains 34 amino acid residues in the following sequence: H A D G T Y T S D V S S Y L Q D Q A A K K F V T W L K Q G Q D R R E. These findings suggest that all three peptides are derived from a common precursor.