Presence of Met-enkephalin-Arg6-Phe7 in molluscan neural tissues.

An extract of pedal ganglia of Mytilus edulis was fractioned by high-pressure liquid chromatography by use of a reverse-phase column. Peak fractions with the same retention time as Met-enkephalin-Arg6-Phe7 were subjected to binding assays in invertebrate neural tissue. The results showed that these fractions have the same binding activities as authentic Met-enkephalin-Arg6-Phe7. The heptapeptide from these fractions was purified by high-pressure liquid chromatography under isocratic conditions. Sequential amino acid analysis showed this peptide to have the same primary structure as Met-enkephalin-Arg6-Phe7. These results indicate that invertebrates such as Mytilus edulis possess enkephalinergic systems similar to those found in in higher organisms.