Reactivity of Manganese and Iron Metalloenzyme Models

锰和铁金属酶模型的反应性

• 批准号: 10442664
• 负责人: David P Goldberg
• 金额: $ 29.12万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10442664
• 关键词: Active Sites; Address; Anabolism; Binding; Biological Process; Biomimetics; Carbon; Catalysis; Cell Nucleus; Charge; Chloride Peroxidase; Complement; Complex; Contracts; Coupled; Cytochrome P450; Diagnostic; Dioxygen; Dioxygenases; Disease; Dissociation; Drug Metabolic Detoxication; Electron Transport; Energy Transfer; Enzyme Reactivation; Enzymes; Event; Exhibits; Family; Free Energy; Funding; Goals; Halogens; Health; Heme; Hemeproteins; Human; Hydrocarbons; Hydrogen Bonding; Hydrogen Peroxide; Hydroxyl Radical; Indoles; Iron; Kinetics; Ligands; Manganese; Measures; Mediating; Metabolism; Metals; Methodology; Methods; Modeling; Modification; Nature; Outcome; Oxidants; Oxidation-Reduction; Oxides; Oxygen; Pathway interactions; Pattern; Play; Porphyrins; Process; Property; Proteins; Protons; Reaction; Research; Role; Series; Structure; Structure-Activity Relationship; System; Techniques; Therapeutic; Thermodynamics; Time; Tryptophan; Tryptophanase; Work; adduct; analog; catalyst; cofactor; cold temperature; computer studies; corrole; design; electronic structure; enzyme mechanism; feasibility testing; indoleamine; knowledge base; metalloenzyme; novel; oxidation; programs; small molecule; stop flow technique

Project Summary Heme proteins participate in many essential biological processes that are important to human health and disease, and they are targets of both diagnostic and therapeutic treatments. An important subset of these proteins are enzymes that activate dioxygen (O2) or its reduced analogs (e.g. H2O2). These enzymes utilize the same iron cofactor to mediate a wide range of reactions, including mono- and dioxygenation of organic substrates, C-H activation, desaturation, and C-C bond cleavage. How nature tunes the metal center and active site of these enzymes to mediate such a wide range of functionality is a question of fundamental significance that continues to motivate significant research. This proposal focuses on the synthesis and reactivity of small- molecule model complexes of key intermediates, and their related bond-making/bond-breaking events, proposed in the mechanisms of the thiolate-ligated heme enzymes Cytochrome P450 (CYP), chloroperoxidase (CPO), and aromatic peroxygenase (APO), and the non-thiolate-ligated heme dioxygenases tryptophan-2,3-dioxygenase (TDO) and indoleamine-2,3-dioxygenase (IDO). The thiolate-ligated heme enzymes are capable of oxidizing hydrocarbon C-H bonds, and the proposed mechanism involves H-atom transfer (HAT) (proton-coupled electron- transfer, PCET) from R-H to an intermediate called Compound-I (Fe=O), followed by hydroxyl transfer (“rebound”) from protonated Compound-II (Fe-OH) to give the ROH product. However, the rebound step can be diverted to other pathways, leading to distinctly different reaction outcomes. Many questions remain regarding the fundamental structural, electronic, thermodynamic and kinetic factors that control both HAT and rebound steps. In contrast, TDO/IDO are proposed to rely on an Fe(O2) adduct and Compound-II as active oxidants, although much remains to be learned about this mechanism. Efforts in this proposal will address these questions through the synthesis and study of biomimetic M=O, M-OH, and M-O2 species that will be prepared with tailored porphyrinoid ligands designed to stabilize these species and allow for their direct study. These ligands include ring-contracted corroles (Crl) and corrolazines (Cz), which have a modified porphyrin nucleus which presents a trianionic (3-) charge to the metal, similar to a thiolate-ligated heme active site. Our previous efforts showed that the Crl and Cz platforms provide access to novel species not seen with conventional porphyrins, including a Cpd-I analog with the same spin ground state as found in CYP and CPO, and the first example of a protonated Cpd-II model. Systematic modifications can be made to these small-molecule models through established synthetic methodologies, providing atomic-level control over their geometric/electronic structures, and providing a means to establish structure-function relationships that can be challenging or impossible to obtain when studying the enzymes alone. The long-term goals of the proposed work are: 1) to address fundamental questions related to heme enzyme reactivity and mechanism, and 2) to build the knowledge base regarding synthetic porphyrinoid complexes for applications in small-molecule activation and catalysis.

项目摘要 血红素蛋白参与许多对人类健康至关重要的基本生物学过程 疾病，它们是诊断和治疗性治疗的靶标。这些重要的子集 蛋白质是激活二恶英（O2）或其减少类似物（例如H2O2）的酶。这些酶利用 相同的铁辅因子介导了广泛的反应，包括有机的单氧和二氧化 底物，C-H激活，去饱和和C-C键裂解。大自然如何调节金属中心和活跃 这些酶的位点介导如此广泛的功能是一个基本意义的问题 这继续进行大量的重要研究。该提案的重点是小型的合成和反应性 提议 在硫醇酯绑扎的血红素酶细胞色素P450（CYP），氯氧化酶（CPO）和 芳族过氧酶（APO）和非硫酸盐绑扎的血红素二加氧酶教tonpophan-2,3-二加氧酶 （TDO）和吲哚胺-2,3-二氧酶（IDO）。硫醇含石的血红素酶能够氧化 碳氢化合物C-H键，所提出的机制涉及H原子转移（HAT）（质子耦合电子 - 转移，PCET）从R-H到称为Compound-I（Fe = O）的中间体，然后进行羟基转移 （“反弹”）从质子化的化合物II（Fe-OH）提供ROH产品。但是，反弹步骤可能是 转移到其他途径，导致明显不同的反应结果。关于 控制帽子和反弹的基本结构，电子，热力学和动力学因素 步骤。相比之下，提议TDO/IDO依靠Fe（O2）加合物和化合物-II作为活性氧化剂， 虽然关于这种机制还有很多待了解。该提案的努力将解决这些问题 通过仿生M = O，M-OH和M-O2物种的合成和研究，将通过量身定制 卟啉类配体旨在稳定这些物种并允许其直接研究。这些配体包括 环合矿石（CRL）和Corrolazines（CZ），它们具有改良的卟啉核，呈现为A 金属的三角离子（3-）电荷类似于硫醇酸盐的血红素活性位点。我们以前的努力表明 CRL和CZ平台提供了对传统卟啉未见的新型物种的访问，包括 CPD-I类似物具有与CYP和CPO相同的自旋基态的类似物，而质子化的第一个例子 CPD-II模型。可以通过已建立的这些小分子模型进行系统的修改 合成方法，提供原子级对其几何/电子结构的控制，并提供 建立结构功能关系的手段，当 单独研究酶。拟议工作的长期目标是：1）解决基本 与血红素酶的反应性和机制有关的问题，以及2）建立知识库 有关在小分子激活和催化中应用的相关合成卟啉复合物。