Mechanisms of Enzymatic Copper-Oxygen Chemistry

利用植物干物质原料制造燃料和化学品的能力是大多数可再生能源战略的关键。细菌和真菌释放各种各样的酶，分解纤维植物物质，如木质素，纤维素和几丁质。一类新的铜酶，称为LPMO，在纤维植物物质的氧化分解过程中利用氧气和过氧化氢的分解能力。确定这些酶用于分解植物物质的分子途径是生物无机化学中的一个持续挑战。该研究项目的目标是揭示有关LPMO酶操作的关键新信息。更深入地了解这些酶的功能可以指导合成催化剂的创造，将植物干物质原料转化为生物燃料。该研究项目的跨学科性质使研究生和博士后学生有机会获得各种实验室技能的专业知识。有了这个奖项，生命过程化学项目将资助加州理工学院的Harry Gray教授和Jay Winkler教授研究溶解性多糖单加氧酶（LPMO）如何利用活性氧来分解纤维素聚合物。一个持续的争论围绕着负责催化的氧物种：分子氧或过氧化氢。已经提出了LPMO催化的各种机制，并且大多数涉及高度氧化的铜中心作为关键的反应中间体。为了解决这些尚未解决的机制问题，光化学方法用于（1）在不存在活性氧化合物的情况下氧化LPMO的静止状态，（2）用光谱表征中间体，以及（3）检查其对纤维素底物的反应性。钌标记的细菌溶解性多糖单加氧酶？光敏剂用于产生高度氧化的铜活性位点。氧化酶的特点是由UV？]可见和X？]射线光谱法该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

The ability to use plant dry matter feedstocks for making fuels and chemicals is a critical piece of most renewable energy strategies. Bacteria and fungi release a wide variety of enzymes that decompose fibrous plant matter, such as lignin, cellulose, and chitin. A new class of copper enzymes, known as LPMOs, uses the decomposing capabilities of oxygen and hydrogen peroxide during the oxidative breakdown of fibrous plant matter. Determining the molecular pathways these enzymes use to break down plant matter is a continuing challenge in bioinorganic chemistry. The goal of this research project is to uncover critical new information about the operation of LPMO enzymes. A deeper understanding of how these enzymes function could guide the creation of synthetic catalysts for the conversion of plant dry matter feedstocks into biofuels. The interdisciplinary nature of this research program gives graduate and postdoctoral students the opportunity to gain expertise in a wide variety of laboratory skills.With this award, the Chemistry of Life Processes Program is funding Professor Harry Gray and Professor Jay Winkler of California Institute of Technology to study how lytic polysaccharide monooxygenases (LPMOs) employ reactive oxygen species to break down cellulosic polymers. An ongoing controversy revolves around the oxygen species responsible for catalysis: dioxygen or hydrogen peroxide. Various mechanisms for LPMO catalysis have been proposed, and most implicate a highly oxidized copper center as the critical reactive intermediate. To address these unresolved mechanistic questions, photochemical methods are used to (1) oxidize the resting state of LPMO in the absence of reactive oxygen compounds, (2) characterize the intermediate spectroscopically, and (3) examine its reactivity toward cellulosic substrates. A bacterial lytic polysaccharide monooxygenase enzyme labeled with a ruthenium?]photosensitizer is used to generate the highly oxidized copper active site. The oxidized enzyme is characterized by UV?]visible and X?]ray spectroscopic methods. The reactivity of the oxidized copper center is being evaluated to determine whether it is a likely intermediate in enzymatic catalysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.