Structure's Influence on Reactivity in Metalloenzymes

结构对金属酶反应活性的影响

• 批准号: 8185628
• 负责人: Julia A Kovacs
• 金额: $ 24.43万
• 依托单位: UNIVERSITY OF WASHINGTON
• 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 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8185628
• 关键词: Acidity; Alzheimer' s Disease; Binding Sites; Biological; Biomimetics; Chemistry; Collaborations; Complex; DNA; Dioxygen; Distal; Electronics; Electrons; Enzymes; Evolution; Fatty Acids; Frequencies; Funding; Hydrogen Bonding; Ions; Kinetics; Label; Ligands; Malignant Neoplasms; Measures; Metals; Modeling; Monitor; Nature; Neurotransmitters; Nitric Oxide; Oxidation-Reduction; Oxygen; Parkinson Disease; Process; Property; Relative (related person); Reporting; Research; Series; Steroids; Stretching; Structure; Transition Elements; analog; design; dimer; electron density; follow-up; metalloenzyme; oxidation; prevent; programs; pyridine

DESCRIPTION (provided by applicant): Our research program focuses on understanding how thiolate ligands promote N-O and O-O (O2- and O2) bond activation. Nitric oxide (NO) is frequently used to probe O2 binding sites, and form stable analogues of key metastable Fe-O2 intermediates. The ?NO stretching frequency provides a measure of N-O, and thus O-O bond activating properties. A growing number of metalloenzymes use Mn and Fe interchangeably without altering function, and a majority of these promote O-O bond activation and cleavage, and involve M-dioxygen, -superoxo, -peroxo, and -oxo (M= Mn, Fe) species as key intermediates. These enzymes function to remove toxic O2- radicals implicated in cancer, Alzheimer's, Parkinson's disease, and synthesize key biomolecules such as DNA, neurotransmitters, fatty acids, and steroids. The spectroscopic and reactivity properties of thiolate-ligated Fe- and Mn-peroxo, superoxo, and oxo species remain largely unexplored, and the O2 and O2- chemistry of Mn and Fe is complementary with respect to the spectroscopic visibility and stability of reactive intermediates. For the proposed project period we will design and synthesize new, readily derivatized thiolate ligands, and their corresponding Mn and Fe complexes. By systematically altering substituents we will fine-tune the electronic and steric properties of the molecule, and adjust the redox potential, metal ion Lewis acidity, and relative pKa of the distal versus proximal peroxo oxygens. Using a systematic approach we will attempt to determine which properties are key to promoting reactivity and function. By probing redox potentials and ?NO of structurally analogous Mn/Fe pairs we will examine the tunable nature of the M- SR bond, and establish whether cysteinates can facilitate the interchangeability of Mn and Fe while maintaining function. We will fully characterize our new pyridine/thiolate-ligated Fe-peroxo intermediates formed via O2- reduction, and continue to explore the O2- reactivity of additional pyridine- substituted derivatives. Ultimately we will be looking for correlations between Hammett parameters and reactivity, and determining which properties are key to promoting Fe-O versus O-O bond cleavage. We will continue to look for M3+ (M= Mn, Fe) promoted O2- oxidation activity by monitoring for O2 evolution. Ultimately we will be looking for a catalytic SOD mimic. We will fully characterize our new Mn-dioxygen and Mn-OOR (R= tBu, Cm) intermediates using XAS, MCD, resonance Raman, parallel- mode EPR, and DFT, and examine the kinetics and mechanism of the Mn-dioxygen species formation. We wil attempt to stabilize these intermediates, as well as our new Mn=O, by incorporating steric bulk into the ligand. We will continue to explore the reactivity of our new Mn-dioxygen, Mn-oxo, and Mn- OOR intermediates with oxidizable substrates. PUBLIC HEALTH RELEVANCE: Our research program focuses on understanding how thiolate ligands promote O-O bond activation in Mn- and Fe-containing enzymes that function to remove toxic O2- radicals (implicated in cancer, Alzheimer's, Parkinson's disease), and synthesize key biomolecules (e.g., DNA, and neurotransmitters). The proposed project will determine the metal ion properties that are key to promoting function, and establish whether the tunable nature of M-SR bonds can facilitate the interchangeable use of Mn and Fe without altering function. The spectroscopic and reactivity properties of thiolate-ligated Fe- and Mn-peroxo, superoxo, and oxo species remain largely unexplored, and the O2 and O2- chemistry of Mn and Fe is complementary with respect to the spectroscopic visibility and stability of reactive intermediates.

描述（由申请人提供）：我们的研究项目侧重于了解硫醇盐配体如何促进 N-O 和 O-O（O2- 和 O2）键活化。一氧化氮 (NO) 经常用于探测 O2 结合位点，并形成关键亚稳态 Fe-O2 中间体的稳定类似物。 ΔNO伸缩频率提供了N-O的量度，从而提供了O-O键活化性能的量度。越来越多的金属酶在不改变功能的情况下互换使用 Mn 和 Fe，其中大多数促进 O-O 键活化和裂解，并涉及 M-双氧、-superoxo、-peroxo 和 -oxo (M= Mn, Fe) 物种关键中间体。这些酶的作用是去除与癌症、阿尔茨海默病、帕金森病有关的有毒 O2- 自由基，并合成关键生物分子，如 DNA、神经递质、脂肪酸和类固醇。硫醇盐连接的 Fe- 和 Mn- 过氧、超氧和含氧物种的光谱和反应性质在很大程度上仍未被探索，并且 Mn 和 Fe 的 O2 和 O2- 化学在反应中间体的光谱可见性和稳定性方面是互补的。在拟议的项目期间，我们将设计和合成新的、易于衍生的硫醇盐配体及其相应的锰和铁配合物。通过系统地改变取代基，我们将微调分子的电子和空间性质，并调整氧化还原电位、金属离子路易斯酸度以及远端与近端过氧氧的相对pKa。我们将使用系统方法尝试确定哪些特性对于促进反应性和功能至关重要。通过探测结构类似的 Mn/Fe 对的氧化还原电位和 ?NO，我们将检查 M-SR 键的可调性质，并确定半胱氨酸是否可以促进 Mn 和 Fe 的互换性，同时保持功能。我们将充分表征通过 O2- 还原形成的新型吡啶/硫醇盐连接的 Fe-过氧中间体，并继续探索其他吡啶取代衍生物的 O2- 反应性。最终，我们将寻找哈米特参数和反应性之间的相关性，并确定哪些特性是促进 Fe-O 与 O-O 键断裂的关键。我们将继续通过监测 O2 释放来寻找 M3+（M= Mn、Fe）促进 O2- 氧化活性。最终我们将寻找催化 SOD 模拟物。我们将使用 XAS、MCD、共振拉曼、并联模式 EPR 和 DFT 全面表征我们的新型 Mn-dioxygen 和 Mn-OOR (R= tBu, Cm) 中间体，并检查 Mn-dioxygen 物质形成的动力学和机制。我们将尝试通过将空间体积合并到配体中来稳定这些中间体以及我们的新 Mn=O。我们将继续探索新的 Mn-dioxygen、Mn-oxo 和 Mn-OOR 中间体与可氧化底物的反应活性。 公共健康相关性：我们的研究项目侧重于了解硫醇盐配体如何促进含锰和含铁酶中的 O-O 键活化，这些酶的功能是去除有毒的 O2-自由基（与癌症、阿尔茨海默病、帕金森病有关）并合成关键生物分子（例如，O2-自由基）。 、DNA 和神经递质）。拟议的项目将确定对促进功能至关重要的金属离子特性，并确定 M-SR 键的可调性质是否可以促进 Mn 和 Fe 的互换使用而不改变功能。硫醇盐连接的 Fe- 和 Mn- 过氧、超氧和含氧物种的光谱和反应性质在很大程度上仍未被探索，并且 Mn 和 Fe 的 O2 和 O2- 化学在反应中间体的光谱可见性和稳定性方面是互补的。