Spectroscopic Studies of Thiolate Donors in Mo Enzymes

Mo 酶中硫醇盐供体的光谱研究

• 批准号: 6635385
• 负责人: KATRINA L PEARISO
• 金额: $ 4.64万
• 依托单位: UNIVERSITY OF NEW MEXICO
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6635385
• 关键词: Raman spectrometry; active sites; biochemistry; chemical bond; chemical models; chemical structure function; chemical synthesis; circular magnetic dichroism; electron density; electron spin resonance spectroscopy; electron transport; enzyme activity; enzyme mechanism; heme; hydroxylation; molybdenum; organic acid; oxidation reduction reaction; protein purification; proteolysis; sulfite reductase; sulfur compounds; xanthine oxidase

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.

性状（由申请人提供）：黄嘌呤氧化酶（XO）和亚硫酸盐氧化酶 (SO)是在人体内发现的单核钼酶， Lesch-Nyhan综合征和亚硫酸盐氧化酶缺乏症。两 这些疾病是遗传性疾病， 缺陷，最终死亡。XO也与氧化损伤有关 如在缺血性休克之后发生的。来自EXAFS的一致性结构， 晶体学研究允许新的和更详细的假设， 关于这些酶的作用机制，以下测试 假设将具体解决：（i）O-Mo-Cys（S）-C二面角 亚硫酸盐氧化酶（SO）在调节还原过程中起着关键作用 活性位点的潜力和促进氧原子转移（OAT）。 (ii)除了偶联SO信息有效的活性位点之外， σ介导的电子转移途径，烯-1，2-二硫醇盐起作用， 在选择和激活赤道氧代原子中的关键作用 转移有效地在烯-1，2-二硫醇盐内进行电荷再分配 促进连续的等电位单电子转移。(iii)转化 催化必需的[MoVIOS（SH）]+单元转化为[MoIVO（SH）]+， 在XO酶家族中，羟基化通过形式氢化物转移发生 并且是将活性位点偶联成有效的 超交换途径的电子转移涉及的O-轨道的 吡喃蝶呤拟议中的实验涉及生物化学的组合 操作和合成化学以制备光谱样品 study.