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

项目摘要。单核血红素铁（mnhFe）酶执行一系列化学多样性 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， 关键代谢物和DNA修复。因此，mnhFe酶的错误调节和功能障碍已经被证实。 与许多疾病有关，包括神经变性、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，其激活双氧，形成高度还原的Fe（II）。 反应性FeIII-O2物质。一旦形成，这种FeIII-O2-中间体可以促进大量不同的 反应导致化学反应性的巨大差异。尽管活性位点和非活性位点 (and有时是底物）结构，每种酶都促进高度特异性的反应，并产生高度 具体产品。这些相似的活性位点结构导致如此高的反应特异性的因素是 没有完全理解。本文提出的工作的首要目标是了解FeIII-O2- 两种mnhFe酶半胱氨酸双加氧酶（CDO）和异青霉素-N-合酶（IPNS）中间体可 选择性地促进两个结构相似的底物上的巨大不同的反应：硫氧化（CDO）与 C-H原子提取（IPNS）。 CDO和IPNS都修饰含硫醇的底物，一旦它与铁中心配位。我们假设 这两种酶的不同反应性是由标称S（3 p）型的取向促进的， 轨道的配位底物，这将打开或关闭一个化学上有利的S基氧化 反应为了探索这一假设，我们将准备一个结构相关的金属肽库， 促进CDO或IPNS样化学反应。这些肽之间的主要区别将是 S（3 p）型轨道相对于FeIII-O2-的超氧配体的攻击矢量的取向 中间体因为这些肽的几何和电子结构几乎完全相同， 反应性的差异将归因于S（3 p）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，从而提供了一个 优秀的本科研究人员培训平台。除了仿生金属肽设计和 合成，这些系统将进行机械，光谱（电子吸收，EPR，（M）CD， X射线吸收，振动和穆斯堡尔光谱），和高层次的计算研究。使用 金属酶模拟物在我们的研究中特别值得注意;很少有研究已经进行， 通过基于金属肽的金属酶模拟物揭示了对特定生物化学过程的洞察。 因此，完成这个项目不仅将揭示mnhFe生物化学的有趣方面， 扩大了对基于金属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.