ISOLATION, STRUCTURAL CHARACTERIZATION AND BIOLOGICAL FUNCTION OF A LYSINE-CONOPRESSIN IN THE CENTRAL-NERVOUS-SYSTEM OF THE PHARYNGOBDELLIDLEECH ERPOBDELLA-OCTOCULATA

Several neuropeptides are suspected to act on the control of hydric ba lance in leeches. One of these peptides, a peptide immunoreactive to a n antibody against oxytocin, was previously characterized from the cen tral nervous system of the leech Erpobdella octoculata [Salzet, M., Wa ttez, C., Verger-Bocquet, M., Beauvillain, J.-C. & Malecha, J. (1993) Brain Res. 601, 173-184]. This paper reports the isolation from the ce ntral nervous system of E. octoculata of another peptide of the oxytoc in/vasopressin family; a lysine-vasopressin-like molecule. Its purific ation was performed by reverse-phase high-performance liquid chromatog raphy combined with both dot immunobinding assay and enzyme-linked imm unosorbent assay for lysine-vasopressin. The amino acid sequence was e stablished by Edman degradation and confirmed by electrospray-mass-spe ctrometry measurement. The nonapeptide obtained corresponded to the ly sine-conopressin previously isolated from the venom of the mollusc Con us geographus [Cruz, L. L., de Santos, V., Zafaralla, G. C., Ramilo, C . A., Zeikus, R., Gray, W. R. & Olivera, B. M. (1987) J. Biol. Chem. 2 62, 15821-15824]. In leeches, synthetic lysine-conopressin exerts a di uretic effect which can be compared to that of the arginine-vasopressi n-like peptide isolated in the Insect Locusta migratoria [Proux, J., M iller, C. A., Li, J. P., Carney, R. L., Girardie, A., Delaage, M. & Sc hooley, D. A. (1987) Biochem. Biophys. Res. Commun. 149,180-186].