美国加州大学Yang, Yang研究团队报道了，通过脂肪酸光脱羧酶的再利用和定向进化的立体发散光生物催化自由基环化。相关研究成果发表在2024年4月17日出版的《自然化学》。

尽管天然存在的光酶具有有趣的光物理和光化学活性，但它们尚未被重新用于新的自然活动。

该文中，研究人员设计了脂肪酸光羧化酶，通过利用强氧化激发态黄醌辅因子催化非天然光氧化氧自由基C–C键的形成。通过基因组挖掘、合理工程和定向转化，研究人员开发了一组自由基光环化酶，以促进具有优异的化学、对映和非对映选择性的脱羧自由基环化。该高通量实验工作流程使脂肪酸光羧化酶的定向进化。

研究设计了一组正交的自由基光环化酶，以获得立体化学二元体的所有四种可能的立体异构体，在不对称自由基生物催化中提供完全非对映和对映的生物转化。分子动力学模拟表明，进化出的自由基光环化酶可以很容易地获得近攻击构象，从而实现化学选择性自由基环化。

立体选择性自由基光环化酶的开发在天然光酶家族中，提供了非天然的C–C键形成活性，可用于控制自由基介导的反应的立体化学。

附：英文原文

Title: Stereodivergent photobiocatalytic radical cyclization through the repurposing and directed evolution of fatty acid photodecarboxylases

Author: Ju, Shuyun, Li, Dian, Mai, Binh Khanh, Liu, Xin, Vallota-Eastman, Alec, Wu, Jianping, Valentine, David L., Liu, Peng, Yang, Yang

Issue&Volume: 2024-04-17

Abstract: Despite their intriguing photophysical and photochemical activities, naturally occurring photoenzymes have not yet been repurposed for new-to-nature activities. Here we engineered fatty acid photodecarboxylases to catalyse unnatural photoredox radical C–C bond formation by leveraging the strongly oxidizing excited-state flavoquinone cofactor. Through genome mining, rational engineering and directed evolution, we developed a panel of radical photocyclases to facilitate decarboxylative radical cyclization with excellent chemo-, enantio- and diastereoselectivities. Our high-throughput experimental workflow allowed for the directed evolution of fatty acid photodecarboxylases. An orthogonal set of radical photocyclases was engineered to access all four possible stereoisomers of the stereochemical dyad, affording fully diastereo- and enantiodivergent biotransformations in asymmetric radical biocatalysis. Molecular dynamics simulations show that our evolved radical photocyclases allow near-attack conformations to be easily accessed, enabling chemoselective radical cyclization. The development of stereoselective radical photocyclases provides unnatural C–C-bond-forming activities in natural photoenzyme families, which can be used to tame the stereochemistry of free-radical-mediated reactions.

DOI: 10.1038/s41557-024-01494-0

Source: https://www.nature.com/articles/s41557-024-01494-0