Spectroscopic Studies of Molybdoenzymes and Models

描述（由申请方提供）：组合模型和酶研究 在这个项目中提出的是针对开发一个详细的电子 结构描述吡喃蝶呤钼活性位点，以及它们如何 独特的电子结构与它们的活性机制有关。 计算研究将提供这些活性的价键描述 位点，并帮助我们理解酶-底物相互作用和 过渡状态的性质。该项目的具体目标是： 深入了解黄嘌呤氧化酶（XO）的性质"非常快速" 中间体，并评估该中间体是产品的提议 2）确定末端硫基质子化对Mo-S 键的共价性，以及这可能如何促进电子转移的再生， XO活性位点，3）将硒化物并入XO位点中并执行 对酶的化学修饰形式的光谱研究，4）使用 光谱校准的键合计算来探测反应 XO介导醛和杂环羟基化的配位体 底物，5）确定氧化亚硫酸盐的独特几何结构是否 氧化酶（SO）活性位点指导特定的氧代配体转移到 在还原性半反应中的底物，有效地降低能量， 过渡态，6）确定配位半胱氨酸的作用， 烯-1，2-二硫醇供体在SO的氧化半反应，7）了解 人SO中的A208D突变如何影响SOox中的Mo-S-Cys键合，和/或 SOred，8）确定烯-1，2-二硫醇盐螯合物在电子 DMSO还原酶（DMSOR）的转移（还原）半反应，以及9）了解 配位的丝氨酸在催化中的作用，并探讨其性质。 DMSOR过渡态。酶XO，醛氧化酶（AO）和SO被发现 在人类中，它们对人类健康的重要性体现在 事实上，患有钼辅因子缺乏症的个体显示， 严重的神经系统症状和儿童早期死亡。XO的酶 家族最近已经涉及前药活化，药物代谢， 在特定条件下，NO合酶活性，AO最近被 显示出将泛昔洛韦代谢为有效的抗病毒药物泛昔洛韦， 已经发现对诸如单纯疱疹的病毒感染有效， 水痘带状疱疹、EB病毒和B型肝炎。患有以下疾病的人 孤立的亚硫酸盐氧化酶缺乏症，它来自特定的突变， SO基因表现出多种毁灭性影响，包括神经学影响， 异常、眼透镜脱位、智力迟钝，甚至 大脑发育迟缓

DESCRIPTION (provided by applicant): The combined model and enzyme studies proposed in this project are directed toward developing a detailed electronic structure description pyranopterin molybdenum active sites, and how their unique electronic structures relate to their mechanism of activity. Computational studies will provide a valence bond description of these active sites, and aid in our understanding of enzyme-substrate interactions and the nature of the transition state. The specific aims of the project are toe 1) provide insight into the nature of the xanthine oxidase (XO) 'Very Rapid' intermediate, and assess the proposal that this intermediate is an product bound species, 2) determine the effect of terminal sulfido protonation on Mo-S bond covalency, and how this might facilitate electron transfer regeneration of the XO active site, 3) incorporate selenide into the XO site and perform spectroscopic studies on the chemically modified form of the enzyme, 4) use spectroscopically calibrated bonding calculations to probe the reaction coordinate for XO mediated hydroxylation of aldehyde and heterocyclic substrates, 5) determine whether the unique geometry of the oxidized sulfite oxidase (SO) active site directs a specific oxo ligand for transfer to substrate in the reductive half reaction, effectively lowering the energy of the transition state, 6) ascertain the role of the coordinated cysteine and ene-1,2-dithiolate donors in the oxidative half reaction of SO, 7) understand how the A208D mutation in human SO affects Mo-S-Cys bonding in SOox and/or SOred, 8) determine the role of the ene-l,2-dithiolate chelates in the electron transfer (reductive) half reaction of DMSO reductase (DMSOR), and 9) understand the role of the coordinated serine in catalysis, and probe the nature of the DMSOR transition state. The enzymes XO, aldehyde oxidase (AO), and SO are found in humans, and their importance with respect to human health is exemplified by the fact that individuals suffering from molybdenum cofactor deficiency display severe neurological symptoms and early childhood death. Enzymes of the XO family have recently been implicated in pro-drug activation, drug metabolism, and under specific conditions NO synthase activity, and AO has recently been shown to metabolize famciclovir to the potent antiviral penciclovir, which has been found to be effective against such viral infections as herpes simplex, varicella zoster, Epstein-Barr, and hepatitis B. Individuals who suffer from isolated sulfite oxidase deficiency, which derives from specific mutations in the SO gene, display a variety of deliterious effects including neurological abnormalities, dislocation of the ocular lens, mental retardation, and even attenuated brain growth.