Neuropeptide Y-related peptides from the pancreas of a teleostean (eel), holostean (bowfin) and elasmobranch (skate) fish

Homologous peptides belonging to the pancreatic polypeptide (PP) family were isolated from the pancreas of a teleostean fish, the American eel (Anguilla rostrata), an holostean fish, the bowfin (Amia calva) and an elasmobranch fish, the skate (Raja rhina), and their primary structures were determined. The peptides show stronger homology to neuropeptide Y, particularly in their COOH-terminal regions, than to peptide YY or pancreatic polypeptide and contain an α-amidated COOH-terminal tyrosine residue. The skate peptide Tyr-Pro-Pro-Lys-Pro-Glu-Asn-Pro-Gly-Asp¹⁰-Asp-Ala-Ala-Pro-Glu -Glu-Leu-Ala-Lys-Tyr²⁰-Tyr-Ser-Ala-Leu-Arg-His-Tyr-Ile-Asn-Le u³⁰-Ile-Thr-Arg- Gln-Arg-Tyr-NH₂ represents the first member of the PP family to be isolated from a cartilaginous fish. The primary structure of the pancreatic PP family peptide has been more strongly conserved among the phylogenetically more ancient holostean and elasmobranch fishes than among the teleosts. A comparison of the primary structures of all PP family peptides supports the hypothesis that evolution has acted to conserve features of tertiary structure in the molecules (e.g., the polyproline- and α-helices) rather than individual amino acid residues.