Solid-Phase Library Synthesis, Screening, and Selection of Tight-Binding Reduced Peptide Bond Inhibitors of a Recombinant Leishmania mexicana Cysteine Protease B

摘要

A one-bead-two-compound inhibitor library was synthesized by the split-mix method for the identification of inhibitors of a recombinant cysteine protease from Leishmania mexicana, CPB2.8ΔCTE. The inhibitor library was composed of octapeptides with a centrally located reduced bond introduced by reductive amination of the resin-bound amines with Fmoc amino aldehydes. The library was screened on solid phase, and less than 1% of the library contained active compounds. The inhibitors displayed great specificity in the subsites flanking the enzyme catalytic triad with Cha and Ile/Leu preferred in P_2, Phe in P_1, Cha and Ile/Leu in P_1', and Ile/Leu in P_2'. Some of the inhibitors were resynthesized, and the kinetics of inhibition were determined in solution-phase assays. Most of the inhibitors had micromolar K_i values, and a few inhibited the enzyme at nanomolar concentrations. One inhibitor, DKHF(CH_2NH)LLVK (K_i = 1 μM), was tested for antiparasite efficacy and shown to affect parasite survival with an IC_(50) of approximately 50 μM.