in 2007, followed by postdoctoral studies at York University (UK) and Greifswald University (Germany). In 2010, she transitionedto industry applying and developing biocatalytic technologies at Novacta in the UK, prior to joining Chemical Process Development at GSK, with responsibility for the development and implementation of new biocatalytic technologyi nboth pre-and post-commercialization routes. Since Dec. 2016, Radka is leading the Bioreactions group in GDC at the Novartis Institute for Biomedical Research in Basel, Switzerland. Jeffrey Moore obtained his PhD in Chemical Engineeringf rom the California Institute of Technology in 1996 as Frances Arnold's first Directed Evolution graduate student. His foundational work led to an evolved p-nitrobenzyl esterase and the Lonza Centenary Prize (1997). In 1996, he joined the Biocatalysis Group of Merck & Co.in Rahway NJ, spending two decades inventing new enzymes and new enzymatic processes. In 2018, he transitionedtothe Merck Protein EngineeringG roup responsible for evolving enzymes for the discovery,d evelopmenta nd commercials cale manufacture of medicines. He has been awarded aUS Presidential Green Chemistry Award (2010), the BioCat2012 Award (2012) and the Thomas Edison Inventorship Award (2014). Kai Baldenius studied chemistry in Hamburg and Southampton. He received his PhD for research in asymmetric organometallic catalysis, supervised by H. tom Dieck and H. B. Kagan. After his postdoc on natural product synthesis with K. C. Nicolaou at the Scripps Research Institute he joined BASF in 1993. Kai served BASF in various functions (R&D, production, marketing, sales) before he took the lead of BASF'sbiocatalysis research for almost ad efcade. He left BASF to become afree-lancing consultanti n2019 and in 2020 he has founded Baldenius Biotech Consulting. Uwe T. Bornscheuer studied chemistry and received his PhD in 1993 at Hannover University followed by apostdoc at Nagoya University (Japan). In 1998, he completed his Habilitation at Stuttgart University about the use of lipases and esterasesi n organic synthesis. He has been Professor at the Institute of Biochemistry at Greifswald University since 1999. Beside other awards, he received in 2008 the BioCat2008 Award. He was just recognized as "Chemistry Europe Fellow". His current research interest focuses on the discovery and engineering of enzymes from various classes for applications in organic synthesis, lipid modification, degradation of plastics or complex marine polysaccharides.

N ature has evolved highly efficient systems in the form of cascade reactions, which assemble the metabolic networks that support life (growth and survival). The basic principle of cascade reactions is also frequently used in biocatalysis, using enzymes in isolation, as well as in combination with chemocatalysts (see Fig. 1 and Box 1 for definition of terms) [1][2][3][4][5][6][7] . As there is no need for purification and isolation of intermediates, operating time, production costs and waste are reduced, and concomitantly, overall yields are improved. In addition, the problem of unstable or difficult to handle intermediates can be overcome, and reactivity as well as selectivity can be enhanced by avoiding unfavourable reaction equilibria through the cooperative effects of multiple catalysts 8 . Starting in the 1980s, the early examples of the combination of chemo-and biocatalysts were reported by the van Bekkum group, who pioneered the development of a process to make the sugar substitute d-mannitol from readily available d-glucose through the combination of a heterogeneous metal-catalysed hydrogenation and an enzyme-catalysed isomerization 9 . The first broadly applied technology for the combination of enzyme and metalcatalysts, which was the research subject of many academic groups as well as industry, emerged in the 1990s from the Williams group 10,11 and aimed to achieve higher yields than classical kinetic resolution of racemates, thus overcoming the limitation of a maximum yield of 50% in the latter case. A prominent example of work that developed this theme is the combination of lipase-catalysed kinetic resolution via acylation of secondary alcohols with Pd-or Rh-catalysed racemization via reversible transfer hydrogenation to achieve a dynamic kinetic resolution (DKR) [12][13][14] . This example was facilitated in part because lipases are active and stable in organic solvents. Later, for instance, Turner's group combined a monoamine oxidase-catalysed imine formation with a chemical reduction 15 to achieve the 100% theoretical yield through a deracemization process. In addition to the combination of metalcatalysis with enzymes, organocatalysis, electrochemistry and light-induced reaction couples have since then been studied extensively, going far beyond the scope of a DKR.The challenges to combining chemo-and biocatalysis in cascades (see Box 1 for definitions and Table 1) can be daunting, not least the requirement for the chemical step to occur in the presence of water, the preferred solvent for enzymes 3 . This Review therefore highlights recent examples of the combination of chemo-and biocatalysts in aqueous multistep syntheses, and looks at how to overcome limitations by, for example, design of appropriate reaction conditions, protein engineering and advanced reactor concepts. Furthermore, trends such as the integration of transition metalcatalysis into microorganisms and the introduction of novel chemistry into engineered enzymes are discussed, and a critical assessment of the impact of this research ...

Carboxylic acid reductase enzymes (CARs) meet the demand in synthetic chemistry for a green and regiospecific route to aldehydes from their respective carboxylic acids. However, relatively few of these enzymes have been characterized. A sequence alignment with members of the ANL (Acyl‐CoA synthetase/ NRPS adenylation domain/Luciferase) superfamily of enzymes shed light on CAR functional dynamics. Four unstudied enzymes were selected by using a phylogenetic analysis of known and hypothetical CARs, and for the first time, a thorough biochemical characterization was performed. Kinetic analysis of these enzymes with various substrates shows that they have a broad but similar substrate specificity. Electron‐rich acids are favored, which suggests that the first step in the proposed reaction mechanism, attack by the carboxylate on the α‐phosphate of adenosine triphosphate (ATP), is the step that determines the substrate specificity and reaction kinetics. The effects of pH and temperature provide a clear operational window for the use of these CARs, whereas an investigation of product inhibition by NADP+, adenosine monophosphate, and pyrophosphate indicates that the binding of substrates at the adenylation domain is ordered with ATP binding first. This study consolidates CARs as important and exciting enzymes in the toolbox for sustainable chemistry and provides specifications for their use as a biocatalyst.

Triple mutant K66Q/S149G/N262C (TM_pheDH) of Rhodococcus phenylalanine dehydrogenase (pheDH) was engineered by directed evolution as the first enzyme for the highly enantioselective reductive amination of phenylacetone 1 and 4-phenyl-2-butanone 3, giving (R)amphetamine 2 and (R)-1-methyl-3-phenylpropylamine 4 in >98% ee, respectively. The new amine dehydrogenase TM_pheDH with special substrate specificity is a valuable addition to the amine dehydrogenase family with very limited number, for asymmetric reductive amination of ketone, an important reaction in sustainable pharmaceutical manufacturing. Molecular docking provided insight into the role of key mutations of pheDH, being useful for engineering new amine dehydrogenases with higher activity and unique substrate scope.

Two‐in‐one biocatalysts were engineered by the covalent fusion of NADPH‐dependent Baeyer–Villiger monooxygenases to a phosphite dehydrogenase for coenzyme regeneration (see scheme). Not only the purified fusion proteins, but also whole cells and crude cell extracts containing the enzyme conjugates, could be used to catalyze biotransformations with high efficiency. NADP+=nicotinamide adenine dinucleotide phosphate.

Non‐heme iron halogenases are synthetically valuable biocatalysts that are capable of halogenating unactivated sp3‐hybridized carbon centers with high stereo‐ and regioselectivity. The reported substrate scope of these enzymes, however, is limited primarily to the natural substrates and their analogues. We engineered the halogenase WelO5* for chlorination of a martinelline‐derived fragment. Using structure‐guided evolution, a halogenase variant with a more than 290‐fold higher total turnover number and a 400‐fold higher apparent kcat compared to the wildtype enzyme was generated. Moreover, we identified key positions in the active site that allow direction of the halogen to different positions in the target substrate. This is the first example of enzyme engineering to expand the substrate scope of a non‐heme iron halogenase beyond the native indole‐alkaloid‐type substrates. The highly evolvable nature of WelO5* underscores the usefulness of this enzyme family for late‐stage halogenation.

Biocatalysis is an effective tool to access chiral molecules that are otherwise hard to synthesize or purify. Time-efficient processes are needed to develop enzymes that adequately perform the desired chemistry. We evaluated machine-directed evolution as an enzyme engineering strategy using a moderately stereoselective imine reductase as the model system. We compared machine-directed evolution approaches to deep mutational scanning (DMS) and error-prone PCR. Within one cycle, it was found that machine-directed evolution yielded a library of high-activity mutants with a dramatically shifted activity distribution compared to that of traditional directed evolution. Structure-guided analysis revealed that linear additivity might provide a simple explanation for the effectiveness of machine-directed evolution. The most active and selective enzyme mutant, which was identified through DMS and error-prone PCR, was used for the gram-scale synthesis of the H4 receptor antagonist ZPL389 with full conversion, > 99% ee (R), and a 72% yield.

A unique lipase (SpL) from Sphingomonas sp. HXN-200 was discovered as the first intracellular enzyme for the aminolysis of ester or acid to produce amide. Reactions of a series of esters and amines with SpL gave the corresponding amides 3a–g in high yield with high activity. SpL also showed high enantioselectivity and high activity for enantioselective ester aminolysis, producing amides (R)-3h–j in high ee from the corresponding racemic ester or amine. Moreover, SpL was found to be highly active for the aminolysis of carboxylic acid, which was generally considered infeasible with the known aminolysis enzymes. The aminolysis of several carboxylic acids afforded the corresponding amides 3a, 3d, 3k, 3l, and 3n in good yield. The intracellular SpL was expressed in Escherichia coli cells to give an efficient whole-cell biocatalyst for amide synthesis. Remarkably, high catalytic activity was observed in the presence of water at 2–4% (v/v) for free enzyme and 16% (v/v) for whole cells, respectively. Accordingly, E. coli (SpL) wet cells were used as easily available and practical catalysts for the aminolysis of ester or acid, producing a group of useful and valuable amides in high concentration (up to 103 mM) and high yield. The newly discovered intracellular SpL with unique properties is a promising catalyst for green and efficient synthesis of amides.