Synthetic Nonheme Iron O2 Activation and S-Oxygenation

项目摘要 本提案侧重于激活的基本结构、功能和机械要求 非血红素铁络合物和相关酶对O2的作用。氧气是由非血红素铁中心在 生物学作为一系列重要功能的一部分，包括有机底物的单氧化和双氧化，如 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，使与铁中心结合的硫位置氧化。 这个亚类包括硫醇双加氧酶(TDO)，如哺乳动物的半胱氨酸双加氧酶(CDO)，以及 过硫化物双加氧酶(PDO)，如哺乳动物乙基丙二酸脑病蛋白(ETHE1)。这个 TDO和PDO的作用机制知之甚少，尽管有几种常见的铁/氧 中间体已经被提出。亚砜合成酶EgtB和OvoA是与单核非血红素相关的 利用氧气进行S氧化和C-S键形成的铁酶，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利用铁和氧气。C-S键的形成 IPNS是通过选择性地将碳自由基加到与铁结合的硫上而发生的，这一过程类似于 非血红素铁α-KG卤代酶。一些基本的机械论问题仍然没有得到回答 这些酶。本方案描述了合成非血红素铁化合物的合成和研究。 被设计成模拟与TDO/PDO、亚砜合成酶、IPN、 和α-KG卤代酶。拟议的努力还包括对CDO酶的精选研究，这些研究与 补充模型化合物。该提案的一个重点是表征由Fe/O2衍生的活性物种 它们是被认为在非血红素铁介导的O2激活中起重要作用的关键中间体的类似物。 在结构明确的合成络合物中表征这些物种将提供先例和 支持酶系统中类似的、建议的中间体。建议的可行性，关键 将建立债券订立/违约步骤。用于捕获和/或表征Fe/O2的方法 将使用物种，包括低温和一套先进的分光镜(低温紫外光- 可见光，电子顺磁共振，共振拉曼，穆斯堡尔，X射线吸收)。计算研究 将被用来帮助解释和预测结构和光谱性质以及反应 小路。碳自由基与铁-杂原子键的选择性反应性也将被评估， 独特的一套新的、结构表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的基础知识的重大进步 并选择性地氧化衬底。这些知识也应该为未来的设计提供指导 过渡金属催化剂。这些酶的功能失调被认为与多种疾病有关， 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.