Spectroscopic Studies of Thiolate Donors in Mo Enzymes

描述(申请人提供)：黄嘌呤氧化酶(XO)和亚硫酸盐氧化酶 (所以)在人类体内发现的单核钼酶是与 分别为Lesch-Nyhan综合征和亚硫酸盐氧化酶缺乏症。两个都是 这些疾病是遗传性疾病，会引起重大的神经系统疾病。 缺陷和最终的死亡。XO也与氧化损伤有关 就像发生在缺血性休克之后。源自EXAFS的共识结构和 结晶学研究已经允许新的和更详细的假设 关于这些酶的机制的问题被提出。以下是可测试的 具体假设如下：(I)O-Mo-Cys(S)-C二面角 在调节还原过程中，亚硫酸盐氧化酶(SO)起着关键作用 活性中心的潜力和促进氧原子转移(OAT)。 (二)除耦合活跃站点外，如此信息高效 Sigma介导的电子传递途径--1，2-二硫代烯 原子选择和活化赤道氧基的关键作用 调职。1，2-二硫代烯-1，2-二硫酸酯中有效的电荷再分配 促进顺序等电势单电子转移。(Iii)改装 催化必需的[MoVIOS(SH)]单元到[MoIVO(SH)] 羟基化是通过XO酶家族中的甲酸氢化物转移发生的 并且是将活动站点耦合到高效的 涉及O-轨道的电子转移的超交换途径 吡喃喋呤。拟议中的实验涉及一种生物化学组合 为光谱准备样品的操作和合成化学 学习。

DESCRIPTION (provided by applicant): Xanthine oxidase (XO) and sulfite oxidase (SO) are mononuclear molybdenum enzymes found in humans that have been linked to Lesch-Nyhan syndrome and sulfite oxidase deficiency, respectively. Both of these diseases are genetic disorders that cause significant neurological defects and ultimately death. XO has also been implicated in oxidative injury as occurs following ischemic shock. Consensus structures derived from EXAFS and crystallographic studies have allowed for new and more detailed hypotheses to be put forth concerning the mechanism of these enzymes. The following testable hypotheses will be specifically addressed: (i) The O-Mo-Cys(S)-C dihedral angle in sulfite oxidase (SO) plays a critical role in modulating the reduction potential of the active site and in facilitating oxygen atom transfer (OAT). (ii) In addition to coupling the active site of SO info efficient sigma-mediated pathways for electron transfer the ene-1,2-dithiolate plays a pivotal role in selecting and activating the equatorial oxo group for atom transfer. Charge redistribution within the ene-1,2-dithiolate effectively facilitates sequential isopotential one-electron transfers. (iii) Conversion of the catalytically essential [MoVIOS(SH)]+ unit to [MoIVO(SH)]+ upon hydroxylation occurs via formal hydride transfer in the XO family of enzymes and is a necessary prerequisite for coupling the active site into efficient superexchange pathways for electron transfer involving the o-orbitals of the pyranopterin. The proposed experiments involve a combination of biochemical manipulation and synthetic chemistry to prepare samples for spectroscopic study.