Artificial metalloenzymes as evolvable catalysts for selective chemical synthesis

催化剂是参与化学反应以加速反应的分子，但在此过程中不会被消耗。它们对日常生活至关重要，使科学家能够制造我们生存所需的产品--药物、塑料、服装。一个众所周知的催化例子是Haber-Borsch工艺，它为化肥提供氨，最终帮助养活半个世界。这种人造固氮过程需要高温和高压，使用世界能源供应的1%-2%。相比之下，植物在环境温度和压力下使用金属酶进行固氮。酶和金属酶是自然界的催化剂：随着时间的推移，蛋白质已经演变成高度选择性和高效的催化剂，可以从丰富的自然资源(如糖、水和空气)中制造各种产品。长期以来，化学家们一直试图模仿酶，以追求理想的催化剂，以实现可持续的化学未来，满足社会需求。人工金属酶(ARMS)结合了酶和有机金属催化剂，通过在金属酶中引入前所未有的化学反应能力，在扩大其合成用途的同时，保留了酶的优点，为获得理想的催化剂提供了一个令人兴奋的机会。金属催化剂允许发生广泛的反应，包括激活惰性C-H键(也称为C-H官能化)。两个C-H键转化为C-C键是化学家可用的最有效的转化之一，只有两个氢原子作为废物产生。这些反应在减少废物方面具有巨大的潜力，而且通过避免在C-C键形成之前激活C-H键来减少产物形成所需的化学步骤，从而降低了合成的能量和时间成本。C-H官能化反应很难选择性地进行，因为起始分子中存在许多C-H键，并且分子的固有选择性并不总是产物形成所需的选择性。通过仔细建模和将新的金属中心设计成蛋白质支架，我将创建ARM，它使用蛋白质支架来影响活性部位环境，并导致高度选择性的控制。使用ARM的一个优点是，它们是由DNA编码的，允许使用定向进化-一种基于自然选择的方法-快速优化选择性和活性。使用这种方法，我将为C-H官能化反应创造高度选择性和活性的手臂。手臂的遗传特性还允许它们被转移到细菌细胞中，在细胞内进行非自然的化学反应。我的目标是将这些人造金属酶引入到新的生物合成途径中，以提供获得非天然“天然”产品和其他复杂分子的途径。该项目开发的武器将有可能将非自然活动引入生物体内，并可应用于化学合成以外的领域，包括能源、生物材料和健康应用。

Catalysts are molecules that participate in a chemical reaction to speed it up but are not consumed in the process. They are vital to everyday life enabling scientists to make the products we need to survive - drugs, plastics, clothing. A well know catalytic example is the Haber-Borsch process which provides ammonia for fertiliser that ultimately helps feed the half the world. This man-made nitrogen fixation process requires high temperatures and pressures using 1-2% of the world's energy supply. In contrast, plants perform nitrogen fixation at ambient temperatures and pressures using metalloenzymes. Enzymes and metalloenzymes are nature's catalysts: proteins that have evolved over time to be highly selective and efficient catalysts for making a wide range of products from abundant natural resources, such as sugars, water, and air. Chemists have long sought to mimic enzymes in pursuit of the ideal catalyst for a sustainable chemical future providing for society's needs. Artificial metalloenzymes (ArMs), that combine enzymes and organometallic catalysts, present an exciting opportunity to obtain the ideal catalyst by introducing unprecedented chemical reactivity into metalloenzymes, preserving the benefits of enzymes whilst widening their synthetic utility. Metal catalysts allow a wide range of reactions to occur, including the activation of inert C-H bonds (also known as C-H functionalisation). The transformation of two C-H bonds into a C-C bond represents one of the most efficient transformations available to chemists with only two hydrogen atoms generated as waste. These reactions have enormous potential in reducing waste and also in reducing the number of chemical steps required for product formation by avoiding the need to activate the C-H bond before C-C bond creation, thus lowering the energy and time costs of synthesis.C-H functionalisation reactions are difficult to carry out selectively as many C-H bonds are present in the starting molecules and the innate selectivity of the molecule is not always the desired selectivity for product formation. By carefully modelling and designing new metal centres into protein scaffolds, I will create ArMs, which use the protein scaffold to influence the active site environment and lead to high control of selectivity. One advantage of using ArMs is that they are encoded by DNA allowing the selectivity and activity to be rapidly optimised using directed evolution - a method based on natural selection. Using this approach, I will create highly selective and active ArMs for C-H functionalisation reactions. The genetic nature of the ArMs also allows them to be transferred into bacterial cells to carry out unnatural chemical reactions within a cell. I aim to introduce these artificial metalloenzymes into novel biosynthetic pathways to provide access to unnatural 'natural' products and other complex molecules. The ArMs developed in this project will have the potential to introduce unnatural activities into living organisms, and can be applied in areas beyond chemical synthesis including energy, biomaterials and health applications.