Inhibitory Pentapeptides isolated from the gut of the earthworm, Eisenia foetida

The isolated anterior gut (crop-gizzard) of the oligochaete annelid, Eisenia foetida, was used as a bioassay system to identify the bioactive peptides that regulate rhythmic spontaneous contractions of the gut. Three pentapeptides were purified from the extract of the gut (crop, gizzard and intestine) of the earthworm. These peptides showed inhibitory actions on gut motility and were termed Eisenia inhibitory pentapeptides (EIPPs). EIPPs had the most remarkable effect on the crop among the various parts of the gut with a threshold concentration as low as 10(-10)-10(-9) M. From the pharmacological results, the inhibitory actions of EIPPs on the gut motility seem to be different from those of FMRFamide. The amino acid sequences of EIPPs were very similar to certain molluscan and echiuroid peptides previously identified. This is the first isolation of annelid peptides inhibiting gut motility except for FMRFamide.