SYNTHESIS OF INHIBITORS OF PARASITIC CYSTEINE PROTEASES

该计划的具体目标是设计和合成改进的 cruzain（主要的半胱氨酸蛋白酶）的活性位点定向抑制剂 克氏锥虫 肽模拟物和非肽抑制剂将 设计时应借助以下方面的见解： （一） Fletterick和麦格拉思最近解决的X射线结构， 其在活性位点具有共价结合的Z-Phe-Ala-FMK抑制剂： (ii)了解二肽的结构要求 氟甲基酮（FMK），McKerrow及其同事已经证明 是纯化的cruzain的有效的、不可逆的抑制剂， 在体内对克氏锥虫有活性;和， (iii)结构信息来自DOCK生成的，非 肽类先导抑制剂结构，源自Cohen的工作， 戒指 此外，一类新的基于E-半胱氨酸蛋白酶抑制剂， 将开发64个主题。 具体地，包含以下的抑制剂： 将合成环氧丙酰酮（EPK）亚结构， 由我们的寄生虫学和生物化学合作者， 和恩格尔，在加州大学旧金山弗朗西斯科。 进一步修改和优化 如果有希望的活性， 观察到cruzain抑制剂。 这些工作的重点是确定电极导线的修改 抑制剂结构已经确定（见背景和意义 节），以增强其在体内的使用。 吸收等因素 从口服途径，消除可能有助于 毒副反应，并提高活性和特异性， 将评估针对靶蛋白酶cruzain的抑制剂， 在涉及我们的合成小组的迭代循环中， 蛋白质结构组（麦格拉思，Fletterick和 Craik），以及该计划的寄生虫学和生物化学组成部分 （McKerrow and Engel） 这些共同的努力将导致设计和 合成更加特异和有效的cruzain抑制剂。

The specific aim of this program is to design and synthesize improved active site directed inhibitors of cruzain, the major cysteine protease of Trypanosoma cruzi. Peptide mimetics and non-peptidic inhibitors will be designed with the aid of insights deriving from: (i) The X-ray structure recently solved by Fletterick and McGrath, which has a covalently bound Z-Phe-Ala-FMK inhibitor at the active site: (ii) Knowledge of the structural requirements of the dipeptide fluoromethyl ketones (FMK) that McKerrow and coworkers have demonstrated to be potent, irreversible inhibitors of purified cruzain, and also to be active in vivo against Trypanosoma cruzi; and, (iii) Structural information deriving from the DOCK-generated, non- peptidic lead inhibitor structures deriving from the work of Cohen and Ring. In addition, a new class of cysteine protease inhibitors based on the E- 64 motif will be developed. Specifically, inhibitors incorporating epoxypropionyl ketone (EPK) substructures will be synthesized and evaluated by our parasitology and biochemistry collaborators, McKerrow and Engel, at UC San Francisco. Further modifications and optimization of the initial EPK inhibitors will be performed if promising activity as cruzain inhibitors is observed. The focus of these efforts is to identify modifications of the lead inhibitor structures already identified (see Background and Significance Section) so as to enhance their use in vivo. Factors such as absorption from the oral route, eliminating functional groups that may contribute to toxic side reactions, and enhancing the activity and specificity of the inhibitors against the targeted protease, cruzain, will be evaluated in iterative cycles involving our synthesis group, the computer modeling group (Cohen), the protein structure groups (McGrath, Fletterick and Craik), and the parasitology and biochemistry components of this program (McKerrow and Engel). These combined efforts will lead to the design and synthesis of ever more specific and potent cruzain inhibitors.