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(由申请者提供)：我们的研究项目侧重于了解硫酸盐配体如何促进N-O和O-O(O2-和O2)键的激活。一氧化氮(NO)经常被用来探测O2结合部位，并形成关键的亚稳态Fe-O2中间体的稳定类似物。NO伸缩频率提供了N-O以及O-O键活化性质的量度。越来越多的金属酶在不改变功能的情况下交替使用锰和铁，其中大多数金属酶促进O-O键的活化和断裂，并涉及M-氧、-超氧、-过氧基和-氧(M=Mn，Fe)物种作为关键中间体。这些酶的功能是清除与癌症、阿尔茨海默氏症、帕金森氏症有关的有毒O2-自由基，并合成关键的生物分子，如DNA、神经递质、脂肪酸和类固醇。硫酸酯连接的Fe-和Mn-过氧基、超氧基和氧基物种的光谱和反应性能在很大程度上仍未被探索，而且在反应中间体的光谱可见性和稳定性方面，锰和铁的O2和O2-化学是互补的。在拟议的项目期间，我们将设计和合成新的、易于衍生的硫酸盐配体，以及它们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Lewis酸度和远端与近端过氧基团的相对pKa。使用系统的方法，我们将尝试确定哪些属性是促进反应性和功能的关键。通过探测结构相似的Mn/Fe对的氧化还原势和？NO，我们将考察M-SR键的可调性，并确定半胱氨酸是否能在保持功能的同时促进Mn和Fe的互换。我们将充分表征我们的新的通过O2-还原形成的吡啶/硫酸酯连接的Fe-Peroxo中间体，并继续探索其他吡啶取代的衍生物的O2-反应活性。最终，我们将寻找Hammett参数和反应性之间的相关性，并确定哪些性质是促进Fe-O键与O-O键断裂的关键。我们将继续通过监测O2的释放来寻找M3+(M=Mn，Fe)促进O2-氧化活性。最终，我们将寻找一种催化的超氧化物歧化酶模拟物。我们将用XAS、MCD、共振拉曼、平行模EPR和密度泛函等手段对我们的新的Mn-O2和Mn-OOR(R=TBU，Cm)中间体进行全面的表征，并研究Mn-O2物种形成的动力学和机理。我们将尝试通过在配体中加入空间位阻来稳定这些中间体，以及我们的新的Mn=O。我们将继续探索我们的新的二氧化锰、氧化锰和氧化锰中间体与可氧化底物的反应性。 与公共健康相关：我们的研究计划侧重于了解硫酸盐配体如何促进含锰和含铁的酶中O-O键的激活，这些酶的功能是清除有毒的O2-自由基(与癌症、阿尔茨海默氏症和帕金森病有关)，并合成关键的生物分子(例如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属性，并确定M-SR键的可调性是否可以在不改变功能的情况下促进锰和铁的互换使用。硫酸酯连接的Fe-和Mn-过氧基、超氧基和氧基物种的光谱和反应性能在很大程度上仍未被探索，而且在反应中间体的光谱可见性和稳定性方面，锰和铁的O2和O2-化学是互补的。