Structural characterization of neuropeptide Y from the brain of the dogfish, Scyliorhinus canicula

A peptide of the pancreatic polypeptide (PP) family was isolated in pure form from the brain of an elasmobranch fish, Scyliorhinus canicula (European common dogfish). The primary structure of the peptide was established as: Tyr-Pro-Ser-Lys-Pro-Asp-Asn-Pro-Gly-Glu¹⁰-Gly-Ala-Pro-Ala-Glu-Asp-Leu-Ala-Lys-Tyr²⁰-Tyr-Ser-Ala-Leu-Arg-His- Tyr-Ile-Asn-Leu³⁰-Ile-Thr-Arg-Gln-Arg-Tyr-NH₂. This sequence contains only two amino acid substitutions compared with pig neuropeptide Y (NPY) (Gly for Asp¹¹ and Lys for Arg¹⁹), and two substitutions (Gly for Asp¹¹ and Leu for Met¹⁷) compared with frog NPY. The amino acid sequence of NPY from dogfish brain is appreciably different from the neuropeptide Y-related peptide previously isolated from dogfish pancreas (five amino acid substitutions). The data indicate that evolutionary pressure to conserve the complete primary structure of neuropeptide Y has been very strong. It is suggested that the NPY-related peptide present in the pancreas of elasmobranch and teleost fish represents the piscine equivalent of mammalian peptide tyrosine tyrosine (PYY).