STRUCTURE BASED DRUG DISCOVERY AND MECHANISTIC STUDIES OF PHOSPHORIBOSYLTRANSFER

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。许多寄生虫缺乏嘌呤核苷酸生物合成的新途径，而依赖回收酶，如磷酸核糖基转移酶来获得细胞代谢所需的核苷酸，因此，回收途径为抗增殖药物的发现提供了靶点。此外，我们还对次黄嘌呤/鸟嘌呤磷酸核糖转移酶的作用机理进行了研究。次黄嘌呤/鸟嘌呤磷酸核糖转移酶利用两个二价金属离子，跨越焦磷酸盐离开基团，定位两个底物，并与一个不变的天冬氨酸残基相互作用，催化一个可逆的、有序的、顺序的、亲核的置换反应。锥虫和人酶三元络合物的封闭活性部位形式使我们能够使用天然底物或产物和类似物的组合来分析在正向和反向反应的过渡态之前捕获的结构。以克鲁氏毛滴虫HPRT的闭合活性部位三元底物复合体为靶标，进一步鉴定了几种直接从计算分析中获得的低微摩尔抑制剂。还有更多的化合物有待鉴定。靶标与抑制剂的复合体的结构将允许将预测的结合模式与实际的结合模式进行比较，而寄生虫和人类酶与抑制剂复合体的比较可能有助于提高寄生虫酶的选择性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Many parasites lack de novo pathways for purine nucleotide biosynthesis and rely on salvage enzymes, such as the phosphoribosyltransferases, to acquire those needed for cellular metabolism, thus, the salvage pathways provide targets for anti-proliferative drug discovery. In addition, we are interested in studying the mechanism of hypoxanthine/guanine phosphoribosyltransferases, which catalyze a reversible, ordered, sequential, nucleophilic displacement reaction utilizing two divalent metal ions, which straddle the pyrophosphate leaving group, position the two substrates, and interact with an invariant aspartic acid residue. Closed active site forms of ternary complexes of the Trypanosomza cruzi and human enzymes are available that allow us to analyze structures captured right before the transition states of both the forward and reverse reactions, using a combination of natural substrates or products, and analogs. The closed active site ternary substrates complex of the HPRT from T. cruzi was targeted with DOCK, and several low micromolar inhibitors were further identified that were obtained directly from computational analyses. Many more compounds await characterization. Structures of complexes of the target with inhibitors will allow comparison of predicted to actual binding modes, and comparisons of parasite and human enzymes in complex with inhibitors might lend insight toward improving selectivity for the parasite enzymes.