A MYOMODULIN-CARP-RELATED PEPTIDE ISOLATED FROM A POLYCHAETE ANNELID,PERINEREIS-VANCAURICA

Myomodulin-CARP-family peptides have been isolated only from molluscs. In the present study, a heptapeptide, aLa-Met-Gly-Met-Leu-Arg-Met-NH2 , termed Pev-myomodulin, was isolated from a polychaete annelid, Perin ereis vancaurica using the esophagus of the animal as the bioassay sys tem. The sequence of the annelid peptide is highly homologous with tho se of the myomodulin-CARP-family peptides found in molluscs. The annel id peptide is regarded as a member of the myomodulin-CARP family, thou gh all the molluscan peptides have a Leu-NH2 at their C-termini. The a nnelid peptide showed a potnet contractile action on the esophagus of the annelid. The peptide may be an excitatory neuromediator involved i n the regulation of the esophagus. Among various myomodulin-CARP-famil y peptides and their analogues, the annelid peptide showed the most po tent contractile action on the esophagus. Replacement of the C-termina l Met-NH, of the annelid peptide with a Leu-NH2 decreased its contract ile potency, while replacement of the C-terminal Leu-NH2 of myomodulin and CARP with a Met-NH, increased their potency. The C-terminal Met-N H, of the annelid peptide seems to be important, but not essential, fo r exhibiting its contractile activity on the esophagus. On the anterio r byssus retractor muscle of the bivalve mollusc Mytilus edulis, the a nnelid peptide showed catch-relaxing and contraction-modulating effect s qualitatively similar to those of the authentic peptide CARP, though the annelid peptide was less potent than CARP.