INOSINE MONOPHOSPHATE DEHYDROGENASE

肌苷5 '-单磷酸脱氢酶（IMPDH）是最重要的酶之一。 有吸引力的药物设计目标。 IMPDH催化 IMP转换为XMP，同时减少NAD。这种反应是一种 不寻常的氢化物转移反应; IMP和 Cys残基。 氢化物转移到NAD，留下共价E-XMP* 中间体 E-XMP* 水解产生XMP。 IMPDH反应 控制鸟嘌呤核苷酸的生物合成。 IMPDH抑制剂具有 IMPDH抑制剂的抗增殖活性和临床应用 在病毒、免疫抑制和癌症治疗中得到了很好的应用。 的 微生物和哺乳动物IMPDH之间显著差异表明 这种酶也是抗感染化疗的靶点。 这 提案概述了对该机制的多学科调查 IMPDH催化和抑制剂作用。 这些基本信息 对于进一步开发基于IMPDH的化疗是重要的。 E-XMP* 的形成和水解是特别感兴趣的，因为 免疫抑制药物派考酚酸与E-XMP* 结合。 霉酚酸也是唯一已知的物种选择性抑制剂 关于IMPDH 将确定这种物种选择性的起源。 抗生素oxanosine抑制IMPDH的机制， 将被划定。 IMPDH酶-IMP复合物的结构 莱姆病的病原体伯氏疏螺旋体 完善. 初步结果表明，这种结构将更加 比目前可用的脱辅基酶的晶体结构更有序 和来自胎儿三毛滴虫的IMPDH的E*XMP复合物。 的结构 与抑制剂复合的IMPDH也将得到解决。 这些 实验将利用稳态动力学，预稳态动力学， 定点诱变和X射线晶体学。

Inosine 5'-monophosphate dehydrogenase (IMPDH) is among the most attractive targets for drug design. IMPDH catalyzes the conversion of IMP to XMP with the concomitant reduction of NAD. This reaction is an unusual hydride transfer reaction; an adduct is formed between IMP and a Cys residue. Hydride is transferred to NAD, leaving a covalent E-XMP* intermediate. E-XMP* is hydrolyzed to produce XMP. The IMPDH reaction controls guanine nucleotide biosynthesis. IMPDH inhibitors have antiproliferative activity and the clinical utility of IMPDH inhibitors is well established in viral, immunosuppressive and cancer therapy. The significant differences between microbial and mammalian IMPDH's indicate that this enzyme is also a target for anti-infective chemotherapy. This proposal outlines a multidisciplinary investigation into the mechanism of IMPDH catalysis and inhibitor action. This fundamental information is important for the further development of IMPDH-based chemotherapy. The formation and hydrolysis of E-XMP* is of particular interest because the immunosuppressive drug pycophenolic acid binds to E-XMP*. Mycophenolic acid is also the only known species selective inhibitor of IMPDH. The origin of this species selectivity will be determined. The mechanism of IMPDH inhibition by oxanosine, an antibiotic agent, will be delineated. The structure of the enzyme-IMP complex of IMPDH from Borrelia burgdorferi, the causative agent of Lyme disease, will be refined. Preliminary results suggest that this structure will be more ordered than the currently available crystal structures of the apoenzyme and E*XMP complexes of IMPDH from Tritrichomonas foetus. The structures of IMPDH complexed with inhibitors will also be solved. These experiments will utilize steady state kinetic, pre-steady state kinetic, site-directed mutagenesis and x-ray crystallography.