The GGNG peptides: novel myoactive peptides isolated from the gut and the whole body of the earthworms.

Three novel bioactive peptides, which were structurally related to each other, were purified and chemically identified from two species of the earthworms, Eisenia foetida and Pheretima vittata. One peptide was isolated from the gut tissue of E. foetida, and the other two were purified from the whole body of E. foetida and P. vittata, respectively. These peptides consisted of 17 or 18 amino acid residues and were named GGNG peptides after their unique, common structure of the C-termini. These GGNG peptides augmented both tension and frequency of spontaneous contractions of isolated gut preparations of E. foetida, and also elicited contractions of other annelidan tissues such as the polychaete esophagus and the leech vagina. However, they showed no activity on molluscan or arthropodan tissues, suggesting that GGNG peptides may be peculiar to annelids. No peptides homologous to GGNG peptides have been known so far in any living organisms.