Design and Evolution of Photoenzymes for Triplet Energy Transfer Catalysis

将新的催化模式编程到酶中的能力将对化学和生物技术产生深远影响，提供可持续的生物催化过程来满足社会需求。基因密码扩展技术为生物催化剂的设计和工程开辟了令人兴奋的新机遇，它允许将新的功能元件作为非正则氨基酸侧链选择性地引入蛋白质中。在TRIPase中，我将利用一种扩展的遗传密码来开发高效、选择性和可编程的光酶，这种酶通过三重态能量转移过程运行，这是有机合成中一种目前无法通过生物催化实现的多功能反应模式。这些光酶将包含利用光能和促进有价值的化学反应所需的功能元素，包括[2+2]环加成、电环化、重排和去去化。我的方法将使用工程翻译组件将有机光敏剂引入蛋白质活性部位。蛋白质腔为介导对映体选择性光化学提供了诱人和多样的手性环境，底物和关键催化元件可以精确地定位在一个口袋中。由于光敏剂是遗传编码的，因此可以通过定向进化来优化活性光酶，以提高催化效率和量子产率，或者赋予小分子光催化剂难以实现的新功能。对工程光酶的结构和生化分析将有助于揭示增强光催化作用的活性部位特征和机理策略，以指导未来的生物催化剂设计。总体而言，在TRIPase中开发的平台技术将为蛋白质中丰富的新激发态化学打开大门，从而将为开发具有类似于天然酶的效率和特异性的新一代可进化光催化剂奠定基础。

The ability to program new modes of catalysis into enzymes would have profound impacts across chemistry and biotechnology, delivering sustainable biocatalytic processes to address societal needs. Genetic code expansion technology opens up exciting new opportunities in biocatalyst design and engineering, by allowing site-selective introduction of new functional elements into proteins as non-canonical amino acid side chains. In TRIPase, I will exploit an expanded genetic code to develop efficient, selective and programmable photoenzymes that operate via triplet energy transfer processes, a versatile mode of reactivity in organic synthesis that is currently not accessible to biocatalysis. These photoenzymes will contain functional elements needed to harness light energy and promote valuable chemical reactions including [2+2]cycloadditions, electrocyclizations, rearrangements and deracemizations. My approach will employ engineered translation components to introduce organic photosensitizers into protein active sites. Protein cavities offer attractive and versatile chiral environments for mediating enantioselective photochemistry, where substrates and key catalytic elements can be accurately positioned within a single pocket. Since the photosensitizers are genetically encoded, active photoenzymes can be optimized via directed evolution to enhance catalytic efficiency and quantum yields, or to impart new functions that are challenging to achieve with small molecule photocatalysts. Structural and biochemical analysis of engineered photoenzymes will shed light on the active site features and mechanistic strategies responsible for enhanced photocatalysis to guide future biocatalyst design. Overall, the platform technology developed in TRIPase will open the door to a wealth of new excited-state chemistry in proteins and in doing so will underpin the development of a new generation of evolvable photocatalysts with efficiencies and specificities akin to natural enzymes.