EPR and Mossbauer Characterization of Mn and Fe Proteins, Models, Intermediates

Mn 和 Fe 蛋白质、模型、中间体的 EPR 和穆斯堡尔表征

• 批准号: 8462633
• 负责人: MICHAEL P HENDRICH
• 金额: $ 27.51万
• 依托单位: CARNEGIE-MELLON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-05-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8462633
• 关键词: Active Sites; Aerobic; Affect; Alzheimer' s Disease; Anabolism; Aromatic Compounds; Binding; Biochemical; Biological; Biomimetics; Carbon; Catalysis; Cataract; Catechols; Cerebral Malaria; Chemicals; Chemistry; Complex; Computer software; Data; Dioxygen; Dioxygenases; Electronics; Enzymes; Freezing; Goals; HIV Infections; Heme; Human; Huntington Disease; Hydrogen Bonding; Indoles; Ischemic Brain Injury; Kinetics; Kynurenine; Lead; Life; Ligands; Measures; Metals; Methodology; Modeling; N' -formylkynurenine; Nature; Neurotransmitters; Organism; Oxidation-Reduction; Oxygen; Pathway interactions; Physiological; Property; Proteins; Reaction; Recovery; Research; Route; Series; Serotonin; Site; Spectrum Analysis; Superoxides; System; Techniques; Tryptophan; Tryptophanase; cofactor; electronic structure; extracellular; heme a; insight; metalloenzyme; novel; oxidation

DESCRIPTION (provided by applicant): Life for all aerobic organisms, including humans, depends on the activation of O2 by metals to provide selective and rapid oxidation of biological molecules. Metalloenzymes have evolved a variety of chemical pathways to efficiently utilize the oxidizing power of abundant O2. Mn and non-heme Fe dioxygenases catalyze the cleavage of the aromatic ring of the substrate with incorporation of both oxygen atoms from O2. This reaction is a key step in the ability of Nature to reclaim large quantities of carbon sequestered in aromatic compounds. Tryptophan 2,3-dioxygenase (TDO) catalyzes the insertion of dioxygen and oxidative cleavage of the indole ring of L-tryptophan (L-Trp), converting it to N-formylkynurenine (NFK). The kynurenine pathway constitutes the major route of de novo biosynthesis of NAD, one of the essential redox cofactors in all living systems. The alteration of intermediate metabolites of this pathway can lead to numerous physiological and pathological conditions, including: cataract formation, cerebral malaria, Alzheimer's disease, HIV infection, Huntington's disease and ischemic brain injury. TDO is responsible for oxidizing over 99% of the free L-Trp in intracellular and extracellular pools. In addition, the levels of tryptophan regulated by TDO can affect the synthesis of serotonin, a known neurotransmitter. These two classes of enzymes represent two such fundamental differences in how Nature has evolved strategies for efficient substrate oxidation. The active metal site of the Mn and non-heme Fe dioxygenases has available metal coordination sites for both the substrate and O2. In contrast, the heme containing TDO has only one available metal coordination site, which binds O2, and the substrate L-Trp binds to the protein in a pocket close, but away from the Fe. Biomimetic model complexes will be studied to both enhance our ability to interpret complicated electronic properties of biomolecules and to aid our understanding of the structural and chemical aspect of metalloenzymes that are important in catalysis. Our goal in this proposal is to provide insight into how these enzymes perform their function by studying the atomic level changes that occur in the metal active site as the enzymes turn over their natural substrate. It is anticipated that such studies will provide a better understanding of how Nature constructs enzymatic active sites to perform selective and efficient oxidation of substrates. This research is made possible by our advances in EPR methodology. We have created software for the interpretation of EPR spectra which allows an unprecedented ability to quantitatively characterize virtually all paramagnetic metal sites in proteins and enzymes.

描述（由申请人提供）：所有需氧生物（包括人类）的生命取决于金属对O2的活化，以提供生物分子的选择性和快速氧化。金属酶已经进化出多种化学途径来有效地利用丰富的O2的氧化能力。 Mn和非血红素Fe双加氧酶催化底物的芳环的裂解，并结合来自O2的两个氧原子。这个反应是大自然能够回收大量芳香化合物中的碳的关键一步。 色氨酸2，3-双加氧酶（TDO）催化双氧的插入和L-色氨酸（L-Trp）吲哚环的氧化裂解，将其转化为N-甲酰犬尿氨酸（NFK）。犬尿氨酸途径构成NAD（所有生命系统中的必需氧化还原辅因子之一）从头生物合成的主要途径。该途径的中间代谢物的改变可导致许多生理和病理状况，包括：白内障形成、脑型疟疾、阿尔茨海默病、HIV感染、亨廷顿病和缺血性脑损伤。TDO负责氧化细胞内和细胞外库中超过99%的游离L-Trp。此外，由TDO调节的色氨酸水平可以影响血清素（一种已知的神经递质）的合成。 这两类酶代表了自然界如何进化出有效底物氧化策略的两个根本差异。Mn和非血红素Fe双加氧酶的活性金属位点具有用于底物和O2的可用金属配位位点。相反，含血红素的TDO只有一个可用的金属配位位点，其结合O2，并且底物L-Trp在接近但远离Fe的口袋中结合到蛋白质。 将研究仿生模型复合物，以提高我们解释生物分子复杂电子性质的能力，并帮助我们理解在催化中重要的金属酶的结构和化学方面。 我们在这项提案中的目标是通过研究当酶翻转其天然底物时金属活性位点中发生的原子水平变化来深入了解这些酶如何执行其功能。预计这样的研究将提供一个更好的理解自然如何构建酶活性位点进行选择性和有效的氧化底物。 我们在EPR方法上的进步使这项研究成为可能。我们已经创建了用于解释EPR谱的软件，该软件允许前所未有的能力来定量表征蛋白质和酶中几乎所有的顺磁性金属位点。