Structure/Function of Mn and Fe Superoxide Dismutases

Mn 和 Fe 超氧化物歧化酶的结构/功能

• 批准号: 6640333
• 负责人: Thomas Christian Brunold
• 金额: $ 14.55万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-05 至 2007-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6640333
• 关键词: active sites; atomic absorption spectrometry; biomimetics; catalyst; chemical substitution; circular dichroism; electron spin resonance spectroscopy; electronic spectra; enzyme activity; enzyme structure; iron; manganese; mathematical model; metalloenzyme; molecular dynamics; oxidative stress; protein structure function; superoxide dismutase

DESCRIPTION (provided by applicant): Superoxide dismutases (SODs) are metalloenzymes containing Mn, Fe, Cu/Zn, or Ni active sites that defend biological systems against oxidative damage mediated by the superoxide radical anion (O2), a product of aerobic metabolism. SODs have also been shown to protect against inflammation and are involved in a range of anti-cancer and anti-aging mechanisms. This proposal focuses on the structurally similar Mn- and Fe-dependent SODs, which accomplish their function through disproportionation of O2 to 02 and H202.The long-term objectives of the research outlined in this proposal are- to identify key geometric and electronic structure contributions to the reactivities of Mn- and Fe-dependent SODs and- to obtain molecular-level insight into the reaction mechanisms of these enzymes.With these goals in mind, the following specific aims have been formulated:- Generate electronic structure descriptions of the oxidized and reduced Mn- and Fe-SOD active sites.- Explore the factors responsible for SOD metal specificity.- Assess the role of second-sphere amino acids in tuning active site properties.- Define the nature of the substrate-metal interaction for Mn- and Fe-SODs and evaluate key steps in the corresponding catalytic cycles on experimental and theoretical levels.Our approach involves using a combination of spectroscopic tools (absorption, CD, MCD, EPR, and rR) and computational methods (DFT and NBO) to study the native Mn- and Fe-SOD proteins, the catalytically inactive metal-substituted Mn- and Fe-SOD species, and several mutant proteins. These studies will systematically explore geometric and electronic factors contributing to SOD activity.As SOD enzymes demonstrate therapeutic efficacy in animal models of disease states involving superoxide, low molecular weight SOD enzyme mimics (synzymes) have been proposed for the treatment of a variety of diseases. Synzymes could have distinct advantages over natural SOD enzymes as pharmaceutical agents, such as cellular permeability, lack of immunogenicity, longer lifetimes, potential for oral delivery, and lower production costs. Thus, understanding the principles by which the Mn- and Fe-SOD enzymes achieve their remarkably high catalytic rates, in particular the influence of second coordination shell amino acids on active site electronics, could aid significantly in the rational design of SOD mimics for pharmaceutical applications.

描述（由申请人提供）：超氧化物歧化酶 (SOD) 是含有 Mn、Fe、Cu/Zn 或 Ni 活性位点的金属酶，可保护生物系统免受超氧自由基阴离子 (O2)（有氧代谢产物）介导的氧化损伤。 SOD 还被证明可以预防炎症，并参与一系列抗癌和抗衰老机制。该提案重点关注结构相似的 Mn 和 Fe 依赖性 SOD，它们通过 O2 歧化为 O2 和 H2O2 来实现其功能。该提案中概述的研究的长期目标是确定关键的几何和电子结构贡献Mn 和 Fe 依赖性 SOD 的反应性，以及 - 获得对这些酶的反应机制的分子水平洞察。考虑到这些目标，制定了以下具体目标： - 生成电子结构描述氧化和还原的 Mn- 和 Fe-SOD 活性位点。- 探索导致 SOD 金属特异性的因素。- 评估第二球氨基酸在调节活性位点特性中的作用。- 定义底物-金属相互作用的性质Mn-和 Fe-SOD，并在实验和理论水平上评估相应催化循环中的关键步骤。我们的方法涉及结合使用光谱工具（吸收、CD、MCD、EPR 和 rR）和计算方法（DFT 和NBO）来研究天然 Mn- 和 Fe-SOD 蛋白、催化惰性金属取代的 Mn- 和 Fe-SOD 物种以及几种突变蛋白。这些研究将系统地探索影响 SOD 活性的几何和电子因素。 由于 SOD 酶在涉及超氧化物的疾病状态动物模型中显示出治疗功效，因此低分子量 SOD 酶模拟物（合成酶）已被提议用于治疗多种疾病。与天然 SOD 酶相比，合成酶作为药剂具有明显的优势，例如细胞渗透性、缺乏免疫原性、更长的寿命、口服给药的潜力以及更低的生产成本。因此，了解 Mn-和 Fe-SOD 酶实现极高催化速率的原理，特别是第二配位壳氨基酸对活性位点电子的影响，可以极大地帮助合理设计用于药物应用的 SOD 模拟物。