A NOVEL FMRFamide-RELATED PEPTIDE INHELIX:pQDPFLRFamide

Abstract

A novel FMRFamide-like peptide, purified from the ganglia of Helix aspersa, has the amino acid sequence: pyroglutamyl-aspartyl-prolyl-phenylalanyl-leucyl-arginyl-phenylalanine amide (pQDPFLRFamide). Synthetic pQDPFLRFamide was prepared; it is chromatographically and biologically indistinguishable from the natural peptide, confirming the sequence. pQDPFLRFamide is about a hundred times more potent than FMRFamide on the isolated Helix heart, but slightly less potent than FMRFamide on the Busycon radula protractor muscle. Since pQDPRFLRFamide occurs in Helix blood at levels sufficient to excite the isolated Helix heart, it may act as a cardioregulatory hormone.