Power of Biocatalysis for Organic Synthesis Winkler, Christoph K; Schrittwieser, Joerg H; Kroutil, Wolfgang
ACS central science,
01/2021, Volume:
7, Issue:
1
Journal Article
Open access
Biocatalysis, using defined enzymes for organic transformations, has become a common tool in organic synthesis, which is also frequently applied in industry. The generally high activity and ...outstanding stereo-, regio-, and chemoselectivity observed in many biotransformations are the result of a precise control of the reaction in the active site of the biocatalyst. This control is achieved by exact positioning of the reagents relative to each other in a fine-tuned 3D environment, by specific activating interactions between reagents and the protein, and by subtle movements of the catalyst. Enzyme engineering enables one to adapt the catalyst to the desired reaction and process. A well-filled biocatalytic toolbox is ready to be used for various reactions. Providing nonnatural reagents and conditions and evolving biocatalysts enables one to play with the myriad of options for creating novel transformations and thereby opening new, short pathways to desired target molecules. Combining several biocatalysts in one pot to perform several reactions concurrently increases the efficiency of biocatalysis even further.
Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in ...the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.
Light has received increased attention for various chemical reactions but also in combination with biocatalytic reactions. Because currently only a few enzymatic reactions are known, which per se ...require light, most transformations involving light and a biocatalyst exploit light either for providing the cosubstrate or cofactor in an appropriate redox state for the biotransformation. In selected cases, a promiscuous activity of known enzymes in the presence of light could be induced. In other approaches, light-induced chemical reactions have been combined with a biocatalytic step, or light-induced biocatalytic reactions were combined with chemical reactions in a linear cascade. Finally, enzymes with a light switchable moiety have been investigated to turn off/on or tune the actual reaction. This Review gives an overview of the various approaches for using light in biocatalysis.
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 CO2, 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 CO2-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 CO2-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 CO2 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 CO2 derivates, such as formate or methanol, represents a suitable alternative to direct use of CO2 and provide several examples. Our discussion closes with a techno-economic perspective on enzymatic CO2 fixation and its potential to reduce CO2 emissions.
Cytochrome P450 enzymes catalyze a broad set of C–H activation reactions, the most prominent being hydroxylation. This review provides an overview of the regioselectivity (CH
3
-terminal, in-chain, ...and carboxylate-terminal) and the optical purity of the hydroxylation products obtained from fatty acids as far as described, focusing on systems close to preparative application.
Graphical Abstract
The concurrent operation of chemical and biocatalytic reactions in one pot is still a challenging task, and, in particular for chemical photocatalysts, examples besides simple cofactor recycling ...systems are rare. However, especially due to the complementary chemistry that the two fields of catalysis promote, their combination in one pot has the potential to unlock intriguing, unprecedented overall reactivities. Herein we demonstrate a concurrent biocatalytic reduction and photocatalytic oxidation process. Specifically, the enantioselective biocatalytic sulfoxide reduction using (S)‐selective methionine sulfoxide reductases was coupled to an unselective light‐dependent sulfoxidation. Protochlorophyllide was established as a new green photocatalyst for the sulfoxidation. Overall, a cyclic deracemization process to produce nonracemic sulfoxides was achieved and the target compounds were obtained with excellent conversions (up to 91 %) and superb optical purity (>99 % ee).
The power of biocatalysis and photocatalysis was combined in one pot for a concurrent reduction–oxidation sequence to gain access to enantiopure sulfoxides. In a cyclic deracemization process the enantioselective biocatalytic reduction is followed by a non‐stereoselective light‐dependent oxidation to yield the desired target compounds in >99 % ee. rac‐sulfoxides carrying various substituents on the aromatic ring were well accepted by the system.
Competitive sustainable production in industry demands new and better biocatalysts, optimized bioprocesses and cost-effective product recovery. Our review sheds light on the progress made for the ...individual steps towards these goals, starting with the discovery of new enzymes and their corresponding genes. The enzymes are subsequently engineered to improve their performance, combined in reaction cascades to expand the reaction scope and integrated in whole cells to provide an optimal environment for the bioconversion. Strain engineering using synthetic biology methods tunes the host for production, reaction design optimizes the reaction conditions and downstream processing ensures the efficient recovery of commercially viable products. Selected examples illustrate how modified enzymes can revolutionize future-oriented applications ranging from the bioproduction of bulk-, specialty- and fine chemicals, active pharmaceutical ingredients and carbohydrates, over the conversion of the greenhouse-gas CO2 into valuable products and biocontrol in agriculture, to recycling of synthetic polymers and recovery of precious metals.
Actin filaments polymerizing against membranes power endocytosis, vesicular traffic, and cell motility. In vitro reconstitution studies suggest that the structure and the dynamics of actin networks ...respond to mechanical forces. We demonstrate that lamellipodial actin of migrating cells responds to mechanical load when membrane tension is modulated. In a steady state, migrating cell filaments assume the canonical dendritic geometry, defined by Arp2/3-generated 70° branch points. Increased tension triggers a dense network with a broadened range of angles, whereas decreased tension causes a shift to a sparse configuration dominated by filaments growing perpendicularly to the plasma membrane. We show that these responses emerge from the geometry of branched actin: when load per filament decreases, elongation speed increases and perpendicular filaments gradually outcompete others because they polymerize the shortest distance to the membrane, where they are protected from capping. This network-intrinsic geometrical adaptation mechanism tunes protrusive force in response to mechanical load.
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•Lamellipodial actin density co-fluctuates with the size of the projected area•Lamellipodial actin density adapts to changes in membrane tension•Actin branch geometry prescribes adaptations in lamellipodial actin
How do mechanical perturbations influence the density and the geometry of actin networks at the leading edge of migrating cells?
The synergistic combination of biocatalysis and photocatalysis is emerging as powerful tool for the development of sustainable and atom‐efficient synthetic concepts facilitating an enormous portfolio ...of possible reactions which even goes beyond the capabilities found in nature. Here, a cyclic deracemization process is presented tailored for the synthesis of optically pure sulfoxides which are versatile structural motifs in asymmetric synthesis as well as in bioactive compounds. Enantioselective enzyme‐catalyzed reduction of rac‐sulfoxides was combined with a stereo‐unselective photocatalytic oxidation of the corresponding sulfide intermediate. The utilization of the readily accessible and rather inexpensive photocatalyst Eosin Y increases the usability of this synthetic method. To overcome the incompatibility between the photocatalyst Eosin Y and the biocatalytic step, the cyclic deracemization process was performed in a step‐wise fashion via alternated reduction in the darkness and oxidation under illumination. This modular system allowed precise adjustments of reaction parameters yielding the desired sulfoxide targets with up to >99 % ee. Evaluation of the substrate scope including a range of structurally diverse molecules demonstrated its broad applicability.
A cyclic deracemization process that utilizes alternately a biocatalytic enantioselective reduction employing (S)‐selective methionine sulfoxide reductase from Pseudomonas alcaliphila (paMsr) supplemented with DTT as external reducing equivalent, and a stereo‐unselective photocatalytic oxidation reaction using the readily accessible Eosin Y as photocatalyst to achieve chiral sulfoxides is presented. Evaluation of the substrate scope demonstrates a general applicability of this modular system.
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