基于辅因子的光驱动酶催化复合体系

Cofactor-based solar-driven enzymatic catalysis systems

氧化还原酶因其优越的区域、立体和对映体选择性,并具有反应条件温和、低能耗等优点,在医药、食品添加剂和燃料等合成中有重大应用.然而氧化还原酶催化反应需要依赖昂贵的辅因子来提供或接受电子.最近的研究表明可以利用有机(或无机)光敏剂诱导电子转移实现光驱动下的辅因子再生,并通过将光催化和生物催化相结合的方法构成一个基于辅因子的光驱动酶催化体系,实现清洁、高效的化学品合成.本文综述了近年来基于不同辅因子的光驱动酶催化复合体系的研究进展,并概述了光直接激发辅因子驱动酶催化的反应体系,在此基础上对未来的发展进行展望.

Enzymatic catalysis has received tremendous attention owing to its mild reaction conditions,remarkable stereoselectivity and specificity that chemical synthesis methods are technically challenging.Oxidoreductases as the largest group of enzymes in the Enzyme Commission nomenclature play a vital role in a myriad of chemical transformations(e.g.,asymmetric reduction,oxygenation,hydroxylation,epoxidation,Baeyer-Villiger oxidation)with wide applications in food additives,medicine and energy industries.However,these enzymes require costly cofactors,including nicotinamide adenine dinucleotide cofactor(NADH)or its phosphorylated form(NADPH),and the flavin cofactor(FAD)or flavin mononucleotide(FMN),to supply or accept electrons for fulfilling catalytic function.Therefore,how to efficiently regenerate cofactors in situ for sustainably driving enzymatic catalysis reactions is an urgent problem to be solved.To address this issue,scientists have developed a variety of cofactor regeneration methods,including enzymatic regeneration,chemical regeneration,electrochemical regeneration,and solar-driven regeneration.Among them,solar-driven cofactor regeneration is a high-efficient method by which photosensitive materials can capture the clean and sustainable solar energy for in situ regenerating cofactor with a fast rate.Moreover,coupling it with the enzymatic catalysis system to construct solar-driven enzymatic catalysis hybrid system can realize a continuously enzymatic catalysis reaction driven by light energy,making the enzyme catalysis more environmentally friendly and sustainable.The mechanism of the cofactorbased solar-driven enzymatic catalysis hybrid system is to simulate the natural photosynthesis.In natural photosynthesis,photosystems(photosystems Ⅱ and photosystems Ⅰ)capture sunlight and generate the photo-excited electrons.Simultaneously,H_(2)O is oxidized to O_(2) to quench the holes generated in photosystems.The high-energy photo-excited electrons are subsequently transferred to the ferredoxin-nicotinamide adenine dinucleotide phosphate reductase(FNR)via a transport chain.FNR then utilize the electrons to reduce NADP+into NADPH.NADPH,as reducing equivalents,subsequently are used for enzymatic CO_(2) reduction in the Calvin cycle.In the cofactor-based solar-driven enzymatic catalysis system,similar with natural photosynthetic process,photosensitizer could absorb light,and the electrons in the valence band transfer to the conduction band,generating photo-excited electrons,while the holes generated in the valence band are quenched by the electron donor.The photogenerated electrons are then directly transferred to the cofactor or electron mediator,catalyzing the reduction of cofactors.The reduced cofactors subsequently participate in the enzymatic catalysis process,and driving the reaction.Simultaneously,the cofactors are oxidized to the oxidation state.The oxidized cofactor can be reduced by the photosensitive material again,thus sustainably driving the reaction.In some systems,the cofactor itself can also be used as a photosensitizer that can be converted into the reduced state(or the excited state)in presence of light and electron donors,and then drive the enzymatic catalysis reaction.This article reviews the recent progress in the construction of cofactor-based solar-driven enzymatic catalysis systems from three aspects:(1)Nicotinamide cofactor regeneration-based solar-driven enzymatic catalysis systems,(2)flavin cofactor regeneration-based solar-driven enzymatic catalysis systems,and(3)an emerging type of solar-driven enzymatic catalysis system,in which the cofactor itself can be a photosensitizer,excited by light and driving the enzymatic reaction.Owing to the important role of electron donors in cofactor-based solar-driven enzymatic catalysis systems,we also introduce various electron donors and discuss which kind of electron donors is more appropriate for the cofactor-based solar-driven enzymatic catalysis systems.Finally,we illustrate the challenges and problems in the field of cofactor-based solar-driven enzymatic catalysis systems and discuss potential ways to address these problems.