Inhibition of the Trypanosoma cruzi cysteine protease cruzain has been proposed as a therapeutic approach for the treatment of Chagas’ disease. Among the best-studied cruzain inhibitors to date is the vinylsulfone K777 (1), which has proven effective in animal models of Chagas’ disease. Recent structure–activity studies aimed at addressing potential liabilities of 1 have now produced analogues such as N-[(2S)-1-[[(E,3S)-1-(benzenesulfonyl)-5-phenylpent-1-en-3-yl]amino]-3-(4-methylphenyl)-1-oxopropan-2-yl]pyridine-4-carboxamide (4), which is trypanocidal at ten-fold lower concentrations than for 1. We now find that the trypanocidal activity of 4 derives primarily from the inhibition of T. cruzi 14-α-demethylase (TcCYP51), a cytochrome P450 enzyme involved in the biosynthesis of ergosterol in the parasite. Compound 4 also inhibits mammalian CYP isoforms but is trypanocidal at concentrations below those required to significantly inhibit mammalian CYPs in vitro. A chemical-proteomics approach employing an activity-based probe derived from 1 was used to identify mammalian cathepsin B as a potentially important off-target of 1 and 4. Computational docking studies and the evaluation of truncated analogues of 4 reveal structural determinants for TcCYP51 binding, information that will be useful in further optimization of this new class of inhibitors.
抑制克氏锥虫半胱氨酸蛋白酶克鲁赛因已被提议作为治疗查加斯病的治疗方法。到目前为止,最好研究的克鲁赛因抑制剂之一是乙烯磺酮K777(1号),在查加斯病动物模型中已被证明有效。最近的结构活性研究旨在解决1号潜在的缺陷,现已生产出类似物,如N-[(2S)-1-[[(E,3S)-1-(苯磺酰)-5-苯基戊-1-烯-3-基]氨基]-3-(4-甲基苯基)-1-氧代丙-2-基]吡啶-4-羧酰胺(4号),其对克氏锥虫的杀灭作用浓度比1号低十倍。我们现在发现,4号的克氏锥虫活性主要源自对T. cruzi 14-α-去甲基酶(TcCYP51)的抑制,这是寄生虫中麦角固醇生物合成中涉及的一种细胞色素P450酶。化合物4号也抑制哺乳动物CYP同工酶,但在体外的杀灭作用浓度低于明显抑制哺乳动物CYP所需的浓度。利用从1号衍生的活性基因探针的化学蛋白质组学方法,识别出哺乳动物半胱氨酸蛋白酶B作为1号和4号的潜在重要非靶点。计算对接研究和对4号的截断类似物的评估揭示了TcCYP51结合的结构决定因素,这些信息将有助于进一步优化这类新的抑制剂。