Immunochemical and chromatographic analyses of a neuropeptide from the monogenean parasite, Diclidophora merlangI: Evolutionary aspects of the neuropeptide Y superfamily

Abstract

1. A neuropeptide exhibiting pancreatic polypeptide-immunoreactivity (PP-IR) has been isolated and characterised from the parasitic platyhelminth, Diclidophora merlangi. 2. Extracts of whole parasite contained 44.9 ng/g of PP-IR which, following gel permeation chromatography, was resolved as a single molecular species, co-eluting with mammalian PP and neuropeptide Y (NPY). This peptide was subsequently isolated from 45 g of parasite tissue. 3. The purified peptide was found to be C-terminally amidated. However, the parasite peptide did not cross-react with a non-C-terminal PP antiserum under radioimmunoassay conditions indicating that it is not authentic mammalian PP. 4. Using an RIA system employing an antiserum raised to the C-terminal undecapeptide of NPY, together with a battery of additional C-terminal-specific NPY antisera, no IR was exhibited by the parasite peptide. The flatworm parasite, D. merlangi therefore contains a neuropeptide with immunochemical characteristics more analogous to mammalian PP than NPY. 5. Immunochemical examinations of the NPY superfamily peptides from a range of vertebrate species indicated the evolution of C-terminally NPY-like peptides from more C-terminally PP-like peptides.