The Biological Bulletin, Vol 184, Issue 2 216-222, Copyright © 1993 by Marine Biological Laboratory

PHYSIOLOGY

Two S-Iamide Peptides, AKSGFVRIamide and VSSFVRIamide, Isolated from an Annelid, Perinereis vancaurica

O. Matsushima, T. Takahashi, F. Morishita, M. Fujimoto, T. Ikeda, I. Kubota, T. Nose and W. Miki
Zoological Institute, Faculty of Science, Hiroshima University, Higashi-hiroshima 724, Japan

Two peptides, H-Ala-Lys-Ser-Gly-Phe-Val-Arg-Ile-NH2 (AKSGFVRIamide), and H-Val-Ser-Ser-Phe-Val-Arg-Ile-NH2 (VSSFVRIamide) were isolated from a polychaete annelid, Perinereis vancaurica. Both the peptides evoked rhythmic contractions in the esophagus of Perinereis with a threshold as low as 10-10-10-9 M, suggesting that the peptides may be involved in the regulation of gut motility of the animal. The sequences of these peptides are very similar to those of other S-Iamide family peptides which have been previously isolated from an echiuroid worm and some molluses. In particular, the sequence of VSSFVRIamide is identical to that of an echiuroid S-Iamide peptide. All of the molluscan and echiuroid S-Iamide peptides, as well as the annelid peptides, were found to produce contractions in the esophagus of Perinereis. On the other hand, the annelid S-Iamide peptides, as well as the molluscan and echiuroid peptides, were found to inhibit or potentiate contractions elicited by electrical stimulation in echiuroid and molluscan muscles. S-Iamide peptides may be a typical neuropeptide family distributed interphyletically in the Protostomia.