Contribution of Ligand Sets to Oxygen Activation in Iron-dependent Biocatalysts

项目摘要 该项目的中心主题是C-H/C-C键官能化的分子氧活化，这是 有氧生活分子氧是一种强氧化剂，但与基态单重态分子的反应是动力学的 由于自旋禁止的性质，这是不利的。利用氧气的氧化能力， 由于产生活性氧化物质，金属酶经常被需氧生物体用来活化氧 操纵生物分子。血红素和非血红素铁酶是两种最普遍和有效的天然催化剂。 具有代表性的系统已被很好地表征与接近完整的机械描绘。然而，催化 铁依赖性加氧酶的途径与不太常见的配体集缺乏描述，研究强调， 单个系统通常不考虑血红素和非血红素配位之间的内在差异。整体 在该领域中缺乏系统地比较这两个系统关于氧活化和反应性的图片。这 该项目希望通过研究配体集如何对反应结果做出贡献以及为什么 特定的系统利用一种配位而不是另一种配位来进行特定的反应。直接比较的明显挑战 是系统之间的巨大差异：配体供体的选择，活性位点环境，底物结合模式， 和整个蛋白质支架。为了简化协调环境以进行无偏比较， 选择多功能加氧酶，每个加氧酶具有仅通过氮供体连接的铁中心。一个是His连接的血红素- 一种负责吡咯硝基蛋白产生的依赖性酶，促进色氨酸衍生物的显著重排。 另一种是非血红素铁依赖酶，对视觉循环至关重要，它催化氧化烯烃裂解， 使用4-His连接的亚铁进行异构化。对两者的催化机理和结构-功能关系进行了探讨 对酶的了解很少，很少发现配体组介导氧化反应。在五年 基金期间，我们将比较研究血红素和非血红素系统，以解码非典型配体如何设置 促进不寻常的生物转化以及如何通过卟啉环的存在或不存在来调节氧活化。 最终，拟议的研究将利用对铁氧化学的理解，激发设计 仿生复合物和工程生物催化剂，并推进真菌感染的生物医学治疗的潜力 和视力受损

Project Summary The central theme of this project is dioxygen activation for C-H/C-C bond functionalization, which is fundamental for aerobic life. Molecular oxygen is a powerful oxidant, but the reaction with ground-state singlet molecules is kinetically unfavorable due to the spin-forbidden nature. To harness the oxidizing power of oxygen and circumvent the unregulated production of reactive oxidative species, metalloenzymes are frequently employed by aerobic organisms to activate oxygen and manipulate biomolecules. Heme and non-heme iron enzymes are two of the most ubiquitous and potent natural catalysts. Representative systems have been well characterized with near-complete mechanistic delineation. However, catalytic pathways of iron-dependent oxygenases with less common ligand sets lack description, and studies emphasizing an individual system do not often consider the intrinsic differences between heme and non-heme coordination. A holistic picture to systematically compare these two systems regarding oxygen activation and reactivity is deficient in the field. This project desires to fill the knowledge gap by investigating how the ligand sets contribute to reaction outcomes and why a particular system exploits one coordination over the other for a specific reaction. An apparent challenge of direct comparison is the massive variability between systems: the selection of ligand donors, active site environment, substrate-binding mode, and overall protein scaffold. To simplify the coordination environment for an unbiased comparison, two unique multifunctional oxygenases are chosen, each with an iron center ligated only by nitrogen-donors. One is a His-ligated heme- dependent enzyme responsible for pyrrolnitrin production, promoting remarkable rearrangement of a tryptophan derivative. The other is a non-heme iron-dependent enzyme crucial for the visual cycle, which catalyzes oxidative alkene cleavage and isomerization using a 4-His ligated ferrous iron. The catalytic mechanisms and structure-function correlations of both enzymes are poorly understood and the ligand sets are rarely found to mediate oxygenation reactions. Over the five-year funding period, we will comparatively investigate the heme and non-heme systems to decode how the atypical ligand sets promote the unusual biotransformations and how oxygen activation is tuned by the presence or absence of a porphyrin ring. Ultimately, the proposed research will leverage the understanding of iron-oxygen chemistry, inspire the design of biomimetic complexes and engineered biocatalysts, and advance the potential for biomedical treatments for fungal infection and impaired vision.