Isolation and identification of enkephalins in pedal ganglia of Mytilus edulis (Mollusca).

An acid extract of pedal ganglia of the mollusc Mytilus edulis was fractionated by high-pressure liquid chromatography with a reverse-phase column. Peak fractions with retention times of those of [Met]- and [Leu]enkephalin were subjected to binding assays in both invertebrate and vertebrate tissues. The results showed that these fractions have the same binding activities as authentic enkephalins. Peptides from these fractions were purified by high-pressure liquid chromatography under isocratic conditions. Sequential amino acid analyses showed that these peptides have the same primary structures as [Met]- and [Leu]enkephalin. These results with M. edulis suggest that invertebrates possess an enkephalinergic system similar to that of higher organisms.