Spectroscopic Studies of Thiolate Donors in Mo Enzymes

Mo 酶中硫醇盐供体的光谱研究

• 批准号: 6340114
• 负责人: KATRINA L PEARISO
• 金额: $ 3.33万
• 依托单位: UNIVERSITY OF NEW MEXICO
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6340114
• 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）和亚硫酸盐氧化酶 (SO) 是在人类中发现的单核钼酶，它们与 分别与 Lesch-Nyhan 综合征和亚硫酸盐氧化酶缺乏症有关。两者都 这些疾病是导致严重神经系统疾病的遗传性疾病 缺陷并最终死亡。 XO 也与氧化损伤有关 正如缺血性休克后发生的那样。来自 EXAFS 的共识结构和 晶体学研究允许提出新的、更详细的假设 提出有关这些酶的机制。以下可测试 将具体讨论假设： (i) O-Mo-Cys(S)-C 二面角 亚硫酸盐氧化酶 (SO) 在调节还原反应中起着关键作用 活性位点的潜力和促进氧原子转移（OAT）的能力。 (ii) 除了有效耦合SO信息的活性位点 西格玛介导的电子转移途径 ene-1,2-dithiolate 发挥着 在选择和激活原子赤道氧代基团中发挥关键作用 转移。烯-1,2-二硫醇内的电荷重新分布有效 促进顺序等势单电子转移。 (iii) 转换 [MoIVO(SH)]+ 的催化必需的 [MoVIOS(SH)]+ 单元 羟基化通过 XO 酶家族中的形式氢化物转移发生 是活性位点耦合成高效的必要先决条件 涉及 O 轨道的电子转移的超交换途径 吡喃蝶呤。拟议的实验涉及生物化学的结合 操作和合成化学来制备光谱样品 学习。