Spectroscopic Studies of Molybdoenzymes and Models

描述(申请人提供)：模型和酶研究相结合 在这个项目中提出的是针对开发一个详细的电子 结构描述吡喃喋呤钼的活性中心及其如何 独特的电子结构与它们的活性机制有关。 计算研究将提供对这些活性的价键的描述 并有助于我们理解酶-底物相互作用和 过渡状态的性质。该项目的具体目标是TOE 1) 提供对黄嘌呤氧化酶(XO)的性质的洞察“非常迅速” 中间体，并评估该中间体是产品的提议 结合态，2)决定了硫末质子化对钼-S的影响 键的共价性，以及这可能如何促进电子转移再生 XO活性部位，3)将硒化物加入XO部位并执行 酶的化学修饰形式的光谱研究，4)用途 光谱校准的成键计算以探测该反应 XO催化的醛和杂环的羟基化配位 底物，5)决定氧化亚硫酸盐的独特几何形状 氧化酶(SO)活性位点引导特定的氧合配体转移到 底物中的还原半反应，有效地降低了能量 过渡态，6)确定配位半胱氨酸和 了解烯-1，2-二硫代硫酸酯供体在SO氧化半反应中的作用 人类SO中A208D突变如何影响SOOX和/或中的Mo-S-Cys键 审查，8)确定烯-L，2-二硫代络合物在电子中的作用 DMSO还原酶(DMSOR)的转移(还原)半反应，以及9)了解 配位丝氨酸在催化中的作用，并探讨了 DMSOR过渡态。发现了XO、醛氧化酶等酶 在人类身上，它们对人类健康的重要性体现在 钼辅因子缺乏症个体表现为 严重的神经系统症状和儿童早期死亡。XO的酶 家族最近被牵连到前药物激活，药物代谢， 在特定条件下没有合成酶活性，而AO最近 显示能将泛昔洛韦代谢成有效的抗病毒喷昔洛韦，喷昔洛韦具有 已被发现对单纯疱疹病毒等病毒感染有效， 水痘带状疱疹、爱泼斯坦-巴尔和乙肝 分离的亚硫酸盐氧化酶缺乏症，源于特定的突变 SO基因表现出包括神经系统在内的多种有害影响 异常，晶状体脱位，智力低下，甚至 削弱了大脑的发育。

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.