Reversible inhibition of cathepsin L-like proteases by 4-mer pseudopeptides

A library of 121 pseudopeptides was designed to develop reversible inhibito rs of trypanosomal enzymes (cruzain from Trypanosoma cruzi and congopain fr om Trypanosoma congolense). The peptides share the framework: Cha-X1-X2-Pro (Cha = cyclohexyl-alanine, X1 and X2 were phenylalanyl analogs), based on a previous report [Lecaille, F., Authie, E., Moreau, T., Serveau, C., Gauth ier, F. and Lalmanach, G. (2001) Eur. J. Biochem. 268, 2733-2741]. Five pep tides containing a nitro-substituted aromatic residue (Tyr/Phe) and one a 4 -chlorophenylalanine at the X1 position, and 3-(2-naphthyl)-alanine, homocy clohexylalanine or 3-nitro-tyrosine (3-NO2-Tyr) at the X2 position, were se lected. They inhibited congopain more effectively than cruzain, except Cha4 -NO2-Phe-3-NO2-Tyr-Pro which bound the two parasitic enzymes similarly. Amo ng this series, Cha-3-NO2-Tyr-HoCha-Pro and Cha-4-NO2-Phe-3-NO2-Tyr-Pro are the most selective for congopain relative to host cathepsins. No hydrolysi s occurred upon prolonged incubation time with purified enzymes. In additio n introduction of non-proteogenic residues in the peptidyl backbone greatly enhanced resistance to proteolysis by mammalian sera. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All r ights reserved.