Stereochemical control is an important long-standing research topic in synthetic chemistry. Enzymes, as green and highly selective natural chiral catalysts, face constrains in synthetic applications due to their evolution-defined molecular structure and catalytic mechanism. Photocatalysis represents an important strategy to initiate free radical reactions by capturing photon energy to activate the chemical bonds of substrate molecules. As an emerging synthetic tool for asymmetric synthesis, photobiocatalysis merges the advantages of photochemistry and enzyme. Unfortunately, photoenzymes are rather rare in nature. Thus far photoenzymes identified are DNA photolyases, light-dependent protochlorophyllide reductases and blue light-responsive algal photodecarboxylases. Utilization of advanced molecular biotechnologies such as protein engineering and directed evolution under the guidance of chemical mechanisms of photocatalysis enables us to explore unknown photocatalytic functions of natural coenzymes, synergize photocatalysts and enzymes, and rationally design artificial photoenzyme with defined functions. The past few years have witnessed remarkable advances in these aspects, significantly surpassing the spectrum of substrates and reactions of enzyme catalysis, compensating for the scarcity of natural photo-enzymes and expanding the chemical boundaries and synthetic space of biocatalysis. This review summarizes the latest research progress in chemically-driven photoenzymatic asymmetric reactions. Based on their merging modes, the review categorizes the integration of light and enzyme into four classes: coupling of exogenous photocatalysts and native enzymes, photobiocatalysis driven by excitation of electron donor-acceptor complex, direct photoredox catalysis by coenzymes, and energy transfer photobiocatalysis. The chemical mechanism of bond activation by photocatalysis and synergistic control of stereoselectivity by enzyme in these photobiocatalytic systems are discussed in detail. In the end of this review, we also delineate the present challenges of asymmetric photobiocatalysis including the monotonicity of native photoactive cofactors and low catalytic efficiency for abiological reactions. This review also proposes future directions from the perspectives of new natural enzyme mining, expansion of artificial photoenzymes, enzyme de novo design, and whole-cell catalysis, which are anticipated to foster green bio-manufacturing of high-value functional molecules through the fusion of chemistry and biology and push forward the sustainable development of synthetic chemistry.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |