ISOLATION AND STRUCTURAL CHARACTERIZATION OF ENKEPHALINS IN THE BRAINOF THE RHYNCHOBDELLID LEECH THEROMYZON TESSULATUM

This paper reports the purification of four peptides related to enkeph alins from the brain of the leech Theromyzon tessulatum. After reverse -phase HPLC purification, the sequence of the enkephalins (YGGFM, YGGF L, FM, FL) was established by a combination of automated Edman degrada tion, electrospray mass spectrometry measurement, and co-elution exper iments in reverse-phase HPLC with synthetic peptides. ELISA titrations performed on each purified peptide indicated that the major amount wa s borne by the leucine-enkephalin. The ratio of leucine-enkephalin and methionine-enkephalin of 2:1 is in line with previous immunocytochemi cal data obtained on T. tessulatum brains. The presence of enkephalins in T. tessulatum, an animal belonging to the oldest group of coelomat e metazoans (the Annelida) establishes the very ancient phylogenetic o rigin of opioids and their conservation in the course of evolution.