Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz, Austria.
Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Straße 10, 35043 Marburg, Germany.
Chem Rev. 2023 May 10;123(9):5702-5754. doi: 10.1021/acs.chemrev.2c00581. Epub 2023 Jan 24.
Enzymatic carbon dioxide fixation is one of the most important metabolic reactions as it allows the capture of inorganic carbon from the atmosphere and its conversion into organic biomass. However, due to the often unfavorable thermodynamics and the difficulties associated with the utilization of CO, a gaseous substrate that is found in comparatively low concentrations in the atmosphere, such reactions remain challenging for biotechnological applications. Nature has tackled these problems by evolution of dedicated CO-fixing enzymes, i.e., carboxylases, and embedding them in complex metabolic pathways. Biotechnology employs such carboxylating and decarboxylating enzymes for the carboxylation of aromatic and aliphatic substrates either by embedding them into more complex reaction cascades or by shifting the reaction equilibrium via reaction engineering. This review aims to provide an overview of natural CO-fixing enzymes and their mechanistic similarities. We also discuss biocatalytic applications of carboxylases and decarboxylases for the synthesis of valuable products and provide a separate summary of strategies to improve the efficiency of such processes. We briefly summarize natural CO fixation pathways, provide a roadmap for the design and implementation of artificial carbon fixation pathways, and highlight examples of biocatalytic cascades involving carboxylases. Additionally, we suggest that biochemical utilization of reduced CO derivates, such as formate or methanol, represents a suitable alternative to direct use of CO and provide several examples. Our discussion closes with a techno-economic perspective on enzymatic CO fixation and its potential to reduce CO emissions.
酶促二氧化碳固定是最重要的代谢反应之一，因为它允许从大气中捕获无机碳，并将其转化为有机生物质。然而，由于热力学条件往往不利，以及 CO 气体底物的利用存在困难，CO 气体底物在大气中的浓度相对较低，因此这些反应在生物技术应用中仍然具有挑战性。自然界通过进化专门的 CO 固定酶，即羧化酶，并将其嵌入复杂的代谢途径来解决这些问题。生物技术采用这些羧化和脱羧酶对芳香族和脂肪族底物进行羧化，方法是将它们嵌入更复杂的反应级联中，或通过反应工程改变反应平衡。本综述旨在概述天然 CO 固定酶及其机制相似性。我们还讨论了羧化酶和脱羧酶在合成有价值产品方面的生物催化应用，并对提高这些过程效率的策略进行了单独总结。我们简要总结了天然 CO 固定途径，为设计和实施人工碳固定途径提供了路线图，并强调了涉及羧化酶的生物催化级联的例子。此外，我们认为，生物化学利用还原的 CO 衍生物，如甲酸盐或甲醇，是直接使用 CO 的合适替代方案，并提供了几个例子。我们的讨论以酶促 CO 固定的技术经济视角以及它减少 CO 排放的潜力结束。
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