Spectroscopic Studies of Thiolate Donors in Mo Enzymes

Mo 酶中硫醇盐供体的光谱研究

• 批准号: 6517934
• 负责人: KATRINA L PEARISO
• 金额: $ 3.83万
• 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/6517934
• 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.

描述（由申请人提供）：黄嘌呤氧化酶（XO）和亚硫酸氧化酶 （因此）是在人类中发现的单核钼酶 分别为Lesch-Nyhan综合征和亚硫酸氧化酶缺乏症。两个 这些疾病是引起明显神经系统的遗传疾病 缺陷并最终死亡。 XO也与氧化损伤有关 随着缺血性休克的发生。来自EXAF的共识结构和 晶体学研究允许新的，更详细的假设 关于这些酶的机制提出。可测试 假设将被专门解决：（i）O-mo-cys（s）-c二面角 在亚硫酸盐氧化酶（SO）中，在调节还原方面起关键作用 活性位点的电势并促进氧原子转移（OAT）。 （ii）除了耦合SO高效的活动站点外 Sigma介导的电子转移途径ENE-1,2-二硫酸盐扮演A 在选择和激活原子的赤道氧基团中的关键作用 转移。在ENE-1,2-二硫代内有效地充电重新分布 促进顺序等电势一电子转移。 （iii）转换 催化必不可少的[movios（sh）]+单位至[moivo（sh）]+ 羟基化是通过XO酶家族中的正式氢化物转移发生的 并且是将活动站点耦合到有效的必要先决条件 涉及涉及的电子转移的甲级换途径 吡喃翅目。提出的实验涉及生化的组合 操纵和合成化学以制备光谱学样品 学习。