DYNORPHIN-DERIVED PEPTIDES REVEAL THE PRESENCE OF A CRITICAL CYSTEINE FOR THE ACTIVITY OF BRAIN ENDO-OLIGOPEPTIDASE-A

Brain endo-oligopeptidase A, a neuropeptide-metabolizing endopeptidase, has been considered a cysteine-endopeptidase because it is activated by thiols and inhibited by p-hydroxymercuribenzoate or 5,5'-dithiobis-(2- nitrobenzoic acid). The understanding of the unique specificity of endo- oligopeptidase A was useful for the synthesis of affinity labeling compounds containing as a thiol reactive group the Cys-(3-nitro-2-pyridinesulfenyl) group into dynorphin-derived peptides which are among the best substrates and competitive inhibitor of endopeptidase 22.19. Of the ten compounds tested, only peptides containing 8 to 13 amino acid residues caused irreversible inhibition. The fact that the most effective inhibitors had the reactive group either at the P'1 or at P'3 position [nomenclature of Schechter and Berger] would seem to argue that the reactive cysteine is in the vicinity of the active site, or actually involved in the catalytic step. © 1993 Academic Press, Inc.