Synthetic Nonheme Iron O2 Activation and S-Oxygenation

项目概要 该提案重点关注激活的基本结构、功能和机械要求 O2 通过非血红素铁复合物和相关酶。双氧由非血红素铁中心加工 生物学作为一系列关键功能的一部分，包括有机底物的单氧和双氧， 以及C-S和C-卤化物键的形成。有机底物的氧化是由非血红素介导的 铁加氧酶，以及这些酶的一个重要亚类，氧化与铁中心结合的硫位点。 该亚类包括硫醇双加氧酶 (TDO)，例如哺乳动物半胱氨酸双加氧酶 (CDO)，以及 过硫化物双加氧酶（PDO），例如哺乳动物乙基丙二酸脑病蛋白（ETHE1）。的 尽管几种常见的铁/氧 已提出了中间体。亚砜合酶 EgtB 和 OvoA 是相关的单核、非血红素 利用 O2 进行 S-氧化和 C-S 键形成的 Fe 酶，异青霉素 N 也是如此 合成酶（IPNS），在青霉素的生物合成途径中使用 Fe 和 O2。 C-S键的形成 IPNS 通过选择性碳自由基加成到与 Fe 结合的硫上而发生，这一过程类似于 非血红素 Fe α-KG 卤化酶。许多基本的机制问题仍未得到解答 这些酶。该提案描述了合成非血红素铁化合物的合成和研究 旨在模拟与 TDO/PDO、亚砜合酶、IPNS 相关的结构和功能的某些方面 和 α-KG 卤化酶。拟议的工作还包括对 CDO 酶的选择性研究，该研究与 补充模型化合物。该提案的重点是表征反应性 Fe/O2 衍生物质 它们是关键中间体的类似物，被认为在非血红素铁介导的 O2 激活中很重要。 在结构明确的合成复合物中表征这些物种将提供先例和 支持酶系统中类似的拟议中间体。提议的可行性，关键 将建立键合/断键步骤。设计用于捕获和/或表征 Fe/O2 的方法 将使用多种物种，包括低温和一套先进的光谱学（低温紫外- vis、电子顺磁共振、共振拉曼、穆斯堡尔、X 射线吸收）。计算研究 将用于帮助解释和预测结构和光谱特性以及反应 途径。碳自由基与铁杂原子键的选择性反应性也将被评估，采取 具有一组独特的新型、具有结构特征的氢氧化铁络合物的优势。这些研究应该 导致我们关于非血红素铁酶如何激活 O2 的基础知识取得重大进展 并选择性氧化底物。这些知识还应该为未来的设计提供指导 过渡金属催化剂。这些酶的功能失调与多种疾病有关， 包括神经退行性疾病（阿尔茨海默氏症、帕金森氏症）、关节炎、癌症和遗传性疾病。

Project Summary This proposal focuses on the fundamental structural, functional, and mechanistic requirements for the activation of O2 by nonheme iron complexes and related enzymes. Dioxygen is processed by nonheme iron centers in biology as part of a range of critical functions, including the mono- and di-oxygenation of organic substrates, as well as the formation of C-S and C-halide bonds. The oxygenation of organic substrates is mediated by nonheme iron oxygenases, and an important subclass of these enzymes oxygenate sulfur sites bound to the iron center. This subclass includes the thiol dioxygenases (TDOs), such as mammalian cysteine dioxygenase (CDO), and the persulfide dioxygenases (PDOs), such as mammalian ethylmalonic encephalopathy protein (ETHE1). The mechanisms of action of the TDOs and PDOs are poorly understood, although several common iron/oxygen intermediates have been proposed. The sulfoxide synthases EgtB and OvoA are related mononuclear, nonheme Fe enzymes that utilize O2 to carry out both S-oxygenation and C-S bond formation, as does isopenicillin N synthase (IPNS), which employs Fe and O2 in the biosynthetic pathway of penicillin. The C-S bond formation in IPNS occurs via selective carbon radical addition to a sulfur bound to Fe, a process similar to what occurs in nonheme Fe α-KG halogenases. A number of fundamental mechanistic questions remain unanswered regarding these enzymes. This proposal describes the synthesis and study of synthetic nonheme iron compounds designed to model certain aspects of structure and function related to the TDO/PDOs, sulfoxide synthases, IPNS, and the α-KG halogenases. Proposed efforts also include select studies on the enzyme CDO, which parallel and complement the model compounds. A focus of the proposal is to characterize reactive, Fe/O2-derived species that are analogs of key intermediates thought to be important in nonheme iron-mediated O2 activation. Characterization of these species in structurally well-defined synthetic complexes will provide precedent and support for the analogous, proposed intermediates in the enzymatic systems. The feasibility of proposed, key bond-making/bond-breaking steps will be established. Methods designed to trap and/or characterize Fe/O2 species will be used, including low temperatures and a suite of advanced spectroscopies (low-temperature UV- vis, electron paramagnetic resonance, resonance Raman, Mössbauer, X-ray absorption). Computational studies will be employed to help interpret and predict structural and spectroscopic properties as well as reaction pathways. The selective reactivity of carbon radicals with iron-heteroatom bonds will also be assessed, taking advantage of a unique set of new, structurally characterized ferric hydroxide complexes. These studies should lead to significant advances in our fundamental knowledge regarding how nonheme Fe enzymes activate O2 and selectively oxidize substrates. This knowledge should also provide guidance for the design of future transition metal catalysts. The misfunctioning of these enzymes have been implicated in a variety of diseases, including neurodegenerative disorders (Alzheimer's, Parkinson's), arthritis, cancer, and genetic disorders.