ACTIVE SITES OF FREE RADICAL METALLOENZYMES

自由基金属酶的活性位点

• 批准号: 2468897
• 负责人: JAMES W WHITTAKER
• 金额: $ 15.86万
• 依托单位: OREGON GRADUATE INSTITUTE SCIENCE & TECH
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-02-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2468897
• 关键词: Raman spectrometry; X ray crystallography; active sites; atomic absorption spectrometry; chemical kinetics; chemical structure function; circular dichroism; copper; electron spin resonance spectroscopy; enzyme complex; enzyme mechanism; enzyme model; free radicals; galactose oxidase; metal complex; metalloenzyme; protonation

DESCRIPTION: Free radical reactivity resulting from the ease of making and breaking one electron bonds leads to essential roles for radicals in biological catalysis, providing easy paths for fundamental processes like C-C bond formation and cleavage, atom transfer and redox chemistry. Biology has evolved specialized structures to take advantage of this unique reactivity, but the instability of most biological radicals makes them difficult to study in detail. The Whittaker's research is focused on studies of an unusually stable free radical in the active site of galactose oxidase, a protein radical directly participating in active site redox chemistry as a free radical-coupled copper complex. Galactose oxidase has provided a unique opportunity to study the involvement of free radicals in enzyme catalysis, serving as a paradigm for radical catalysis in other systems where the catalytic free radical is less accessible. The research plan is based on a multidisciplinary approach combining biochemistry, synthesis, spectroscopy, and computational methods that give insight into the biological control of radical reactivity. Mechanistic studies including isotope kinetics will explore the role of protons in radical catalysis. Biochemical characterization of galactose oxidase and two functional variants, glyoxol oxidase and glycerol oxidase, will provide a framework for comparing the structure and function of the radicals in these proteins. The comparative anatomy of glyoxal oxidase will be developed through crystallographic and mechanistic studies on wild type and mutant protein. Spectroscopic studies (absorption, circular dichroism (CD), magnetic circular dichroism (MCD), Stark, and electron paramagnetic resonance (EPR) will extend structural information on the essential radicals to the electronic level that relates directly to the origins of chemical reactivity. Low temperature MCD experiments on the active site cupric ion and inorganic models will extend insight into the role of the metal in catalysis. These multiple experimental approaches will be complemented by theoretical modeling of the spectra and ab initio calculations of the electronic structure of the catalytic radical complex.

描述：由于易于制造而产生的自由基反应性 单电子键的断裂导致了自由基的重要作用 在生物催化中，为基本过程提供了简单的途径， 如C-C键的形成和断裂、原子转移和氧化还原化学。 生物进化出专门的结构来利用这一点 独特的反应性，但大多数生物自由基的不稳定性， 很难详细研究。 惠特克夫妇的研究主要集中在 在活性部位的异常稳定的自由基的研究 半乳糖氧化酶是一种蛋白质自由基， 位点氧化还原化学作为自由基耦合的铜络合物。 半乳糖 氧化酶提供了一个独特的机会，研究参与 酶催化中的自由基，作为自由基 在催化自由基较少的其他体系中的催化作用 容易接近 这项研究计划以多学科方法为基础 结合生物化学、合成、光谱学和计算 深入了解生物控制自由基的方法 反应性 包括同位素动力学在内的机制研究将探索 质子在自由基催化中的作用 生物化学表征 半乳糖氧化酶和两种功能变体，乙二醛氧化酶和 甘油氧化酶，将提供一个框架，比较结构 以及这些蛋白质中自由基的功能。 的比较解剖 乙二醛氧化酶将通过晶体学和 野生型和突变蛋白的机制研究。 光谱 研究（吸收，圆二色性（CD），磁性圆二色性（CD）） 二向色性（MCD）、斯塔克（Stark）和电子顺磁共振（EPR）将 将基本自由基的结构信息扩展到 电子水平直接关系到化学的起源 反应性 活性中心铜离子的低温MCD实验 离子和无机模型将扩展对金属作用的认识， 在催化方面。 这些实验方法将 辅以光谱的理论建模和从头算 催化自由基的电子结构计算 复杂.