Metallopeptide Based Mimics of Mononuclear Nonheme Iron Enzymes: Understanding Enzymatic Reactivity Using Designed Metallopeptides

项目摘要。单核非血红素铁(MnhFe)酶执行一系列不同的化学成分 对人类健康的许多不同方面至关重要的反应，包括：抗生素的生物合成、生产 关键代谢物和DNA修复。因此，mnhFe酶的失调和功能障碍一直是 与许多疾病有关，包括神经退行性变、癌症、糖尿病和心血管疾病 疾病。一大类mnhFe酶含有还原的Fe(II)离子，它能激活氧气，形成高度的 活性FeIII-O2-物种。一旦形成，这种FeIII-O2-中间体可以促进大量不同的 化学反应导致化学反应的巨大多样性。尽管Active-Site中有惊人的相似之处 (有时是底物)结构，每个酶促进一个高度特异的反应，并产生一个高度 特定的产品。从这些相似的活性部位结构中导致如此高的反应特异性的因素是 没有完全理解。这里提出的工作的首要目标是理解FeIII-O2是如何- 两种MnhFe酶的中间体，半胱氨酸双加氧酶(CDO)和异青霉素N-合成酶(IPNS)，可以 在结构相似的底物上选择性地促进两个截然不同的反应：硫氧化(CDO)与 C-H原子抽象(IPNS)。 一旦硫醇底物与铁中心配位，CDO和IPNS都会对其进行修饰。我们假设 这两种酶的不同反应活性是由名义S(3p)型的取向促进的 轨道的配位底物，这将开启或关闭热力学有利的S为基础的氧合 反应。为了探索这一假设，我们将准备一个结构相关的金属多肽文库，它将 推广CDO或IPNS类化学物质。这些多肽之间的主要区别将是 S(3p)型轨道相对于FeIII-O2-超氧配体进攻矢量的取向 中级的。因为这些多肽的几何结构和电子结构都将几乎相同， 反应性的差异将归因于S(3p)轨道取向。 这项研究利用了生物无机化学中遇到的大量工具，从而提供了一种 为本科生科研人员提供了极佳的培训平台。除了仿生金属多肽设计和 这些体系将受到机械性的、光谱的(电子吸收、EPR、(M)CD、 X射线吸收、振动和穆斯堡尔光谱学)和高级计算研究。对.的使用 金属酶模拟物在我们的研究中尤其值得注意；很少有研究在以下方面进行 对特定生化过程的洞察通过基于金属多肽的金属酶模拟来揭示。 因此，这个项目的完成不仅将揭示MnhFe生物化学的有趣方面，而且还将 拓展基于金属多肽的金属酶模拟物的研究范围。

Project Abstract. Mononuclear nonheme iron (mnhFe) enzymes perform an array of chemically diverse reactions that are vital to many different aspects of human health including: antibiotic biosynthesis, production of key metabolites, and DNA repair. Thus, the misregulation and dysfunction of mnhFe enzymes have been implicated in a number of disorders including neurodegeneration, cancers, diabetes, and cardiovascular diseases. A large class of mnhFe enzymes contains a reduced Fe(II) ion that activates dioxygen, forming a highly reactive FeIII-O2– species. Once formed, this FeIII-O2– intermediate can promote a large number of different reactions leading to an enormous diversity in chemical reactivity. Despite the surprising similarities in active-site (and sometimes substrate) structures, each enzyme promotes a highly specific reaction and yields a highly specific product. The factors leading to such high reaction specificity from these similar active-site structures are not fully understood. The overarching goal of the work proposed herein is to understand how the FeIII-O2– intermediate in two mnhFe enzymes, cysteine dioxygenase (CDO) and isopenicillin-N-synthase (IPNS), can selectively promote two vastly different reactions on structurally similar substrates: sulfur oxygenation (CDO) vs C-H atom abstraction (IPNS). Both CDO and IPNS modify a thiol-containing substrate once it is coordinated to the iron-center. We hypothesize that the differential reactivity in these two enzymes is promoted by the orientation of the nominal S(3p)-type orbital of the coordinated substrate, which will turn on or off a thermodynamically favored S-based oxygenation reaction. To explore this hypothesis, we will prepare a library of structurally related metallopeptides that will promote either CDO- or IPNS-like chemistries. The major difference between these peptides will be the orientation of the S(3p)-type orbital relative to the vector of attack of the superoxo ligand of the FeIII-O2– intermediate. Because the geometric and electronic structures of these peptides will all be nearly identical, all differences in reactivity will be attributable to the S(3p) orbital orientation. This research makes use of a large number of tools encountered in bioinorganic chemistry, thus providing an excellent training platform for undergraduate researchers. In addition to biomimietic metallopeptide design and synthesis, these systems will be subjected to mechanistic, spectroscopic (electronic absorption, EPR, (M)CD, X-ray absorption, vibrational and Mössbauer spectroscopies), and high-level computational studies. The use of metalloenzyme mimics in our investigations is especially noteworthy; few studies have been performed where insight into specific biochemical processes are revealed through metallopeptide based metalloenzyme mimics. Therefore, completion of this project will not only reveal interesting aspects of mnhFe biochemistry, but will also expand the limits of investigations concerning metallopeptide based metalloenzyme mimics.