CHARACTERIZATION OF ANTIBACTERIAL COOH-TERMINAL PROENKEPHALIN-A-DERIVED PEPTIDES (PEAP) IN INFECTIOUS FLUIDS - IMPORTANCE OF ENKELYTIN, THEANTIBACTERIAL PEAP(209-237) SECRETED BY STIMULATED CHROMAFFIN CELLS

Proenkephalin-A (PEA) and its derived peptides (PEAP) have been descri bed in neural, neuroendocrine tissues and immune cells. The processing of PEA has been extensively studied in the adrenal medulla chromaffin cell showing that maturation starts with the removal of the carboxyl- terminal PEAP(209-239). In 1995, our laboratory has shown that antibac terial activity is present within the intragranular chromaffin granule matrix and in the extracellular medium following exocytosis, More rec ently, we have identified an intragranular peptide, named enkelytin, c orresponding to the bisphosphorylated PEAP(209-237), that inhibits the growth of Micro coccus luteus (Goumon, Y., Strub, J. M., Moniatte, M. , Nullans, G., Poteur, L., Hubert, P., Van Dorsselaer, A., Aunis, D., and Metz-Boutigue, M. H. (1996) Eur. J. Biochem. 235, 516-525). As a c ontinuation of this previous study, in order to characterize the biolo gical function of antibacterial PEAP, we have here examined whether th is COOH-terminal fragment is released from stimulated chromaffin cells and whether it could be detected in wound fluids and in polymorphonuc lear secretions following cell stimulation. The antibacterial spectrum shows that enkelytin is active against several Grampositive bacteria including Staphylococcus aureus, but it is unable to inhibit the Gram- negative bacteria growth. In order to relate the antibacterial activit y of enkelytin with structural features, various synthetic enkelytin-d erived peptides were tested. We also propose a computer model of synth etic PEAP(209-237) deduced from H-1 NMR analysis, in order to relate t he antibacterial activity of enkelytin with the three-dimensional stru cture. Finally, we report the high phylogenetic conservation of the CO OH-terminal PEAP, which implies some important biological function and we discuss the putative importance of enkelytin in the defensive proc esses.