PROTONATION OF O AND S IN METALLOPROTEINS AND MODELS

金属蛋白质和模型中 O 和 S 的质子化

• 批准号: 3568415
• 负责人: JACK R NORTON
• 金额: $ 8.72万
• 依托单位: COLORADO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-04-01 至 1996-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3568415
• 关键词: chemical kinetics; chemical models; deuterium oxide; ligands; metalloproteins; oxides; protein structure; protonation; sulfides; water

This investigation will determine rate constants for proton transfer to and from bridging and terminal oxo and sulfide ligands in metalloproteins and model systems. By comparing the rate of reactivity of enzymes in H20 vs D20 we hope to establish fraction factors (preference for deuterium over hydrogen) and proton inventories (the number of protons involved in the rate-determining step). These studies should tell us which metalloproteins show slow proton transfer to or from oxygen or sulfur. Because of experimental limitations in protein systems (they cannot withstand large amount of acid or base, or high temperatures), systems which model different metalloprotein active sites will also examined. An understanding of these protonation reactions in model systems will shed light on the important but poorly understood reaction mechanisms of many metalloenzymes. Metalloproteins which contain oxo or sulfide bridges range from hemerythrin through ribonucleotide reductases and methane monooxygenase to the ferredoxin and high potential redox proteins. We will examine the reduction of iron center in the R2 unit of ribonucleotide reductase, and the catalytic activity of purple acid phosphatase and manganese catalase (which take part in many biological processes such as photosynthesis). The significance of protonations in such mechanisms is emphasized by the recent discovery that the intrinsic barrier (i.e. barrier at thermoneutrality) to protonation at bridging oxo ligands is much larger than at an ordinary oxygen. This study will determine if this result is general for all types of systems including biological ones, and compare the rates of protonation of oxo bridges with those of sulfide bridges and of terminal oxo and sulfide ligands.

这项研究将确定质子转移到 以及来自金属蛋白中的桥连和末端氧代和硫化物配体 和模型系统。 通过比较酶在H2O中的反应速率， 与D20相比，我们希望建立分数因子（首选氘 氢）和质子库存（参与氢的质子数）。 速率确定步骤）。 这些研究应该告诉我们 金属蛋白质显示出缓慢的质子转移到氧或硫或从氧或硫转移质子。 由于蛋白质系统的实验限制（他们不能 耐受大量酸或碱，或高温），系统 也将研究其模拟不同的金属蛋白活性位点。 对模型系统中这些质子化反应的理解将 揭示了重要但知之甚少的反应机制， 许多金属酶。 含有氧桥或硫桥的金属蛋白范围包括 血红蛋白通过核糖核苷酸还原酶和甲烷单加氧酶 铁氧还蛋白和高电位氧化还原蛋白。 我们会研究 - 核糖核苷酸还原酶的R2单元中的铁中心的还原，和 紫色酸性磷酸酶和锰过氧化氢酶的催化活性 （参与许多生物过程，如光合作用）。 质子化在这种机制中的重要性是强调的， 最近发现，固有势垒（即， 热中性）对桥氧代配体处的质子化的影响大得多 比普通氧气要多。 这项研究将确定这一结果是否是 一般适用于所有类型的系统，包括生物系统，并比较 氧桥的质子化速率与硫桥的质子化速率， 末端氧和硫化物配体。