Biocatalytic Promiscuity

Redox Out of the Box: Catalytic Versatility Across NAD(P)H-Dependent Oxidoreductases

The asymmetric reduction of double bonds using NAD(P)H-dependent oxidoreductases has proven to be an efficient tool for the synthesis of important chiral molecules in research and on industrial scale. These enzymes are commercially available in screening kits for the reduction of C=O (ketones), C=C (activated alkenes), or C=N bonds (imines). Recent reports, however, indicate that the ability to accommodate multiple reductase activities on distinct C=X bonds occurs in different enzyme classes, either natively or after mutagenesis. This challenges the common perception of highly selective oxidoreductases for one type of electrophilic substrate. Consideration of this underexplored potential in enzyme screenings and protein engineering campaigns may contribute to the identification of complementary biocatalytic processes for the synthesis of chiral compounds. This review will contribute to a global understanding of the promiscuous behavior of NAD(P)H-dependent oxidoreductases on C=X bond reduction and inspire future discoveries with respect to unconventional biocatalytic routes in asymmetric synthesis.

Experimental and computational investigation of the α-amylase catalyzed Friedel-Crafts reaction of isatin to access symmetrical and unsymmetrical 3,3',3''-trisindoles

Trisindoles are of tremendous interest due to their wide range of biological activities. In this context, a number of methods have been reported in the past to synthesize 3,3',3''-trisindoles. However, most of the methods are only able to produce symmetrical 3,3',3''-trisindoles. Herein, we develop a sustainable and efficient approach to synthesize symmetrical as well as unsymmetrical 3,3',3''-trisindoles in a very selective manner using the α-amylase enzyme as a catalyst. Furthermore, various differently substituted isatin and indoles were used to prove the generality of the protocol and symmetrical or unsymmetrical 3,3',3''-trisindoles were obtained in 43-97% isolated yields. Next, a probable mechanism is proposed and investigated using molecular dynamics (MD) investigation to gain more insight into the role of residues available in the active site of the α-amylase enzyme. These studies revealed that Glu230, Lys209, and Asp206 in the active site of α-amylase play an important role in this catalysis. Moreover, the DFT studies suggested the formation of bisindole and alkylideneindolenine intermediates during the transformation. We synthesized four different biologically important 3,3',3''-trisindoles on a gram scale, which proved the robustness and scalability of this protocol.

Qualitative metabolomics-based characterization of a phenolic UDP-xylosyltransferase with a broad substrate spectrum from Lentinus brumalis

Wood-decaying fungi are the major decomposers of plant litter. Heavy sequencing efforts on genomes of wood-decaying fungi have recently been made due to the interest in their lignocellulolytic enzymes; however, most parts of their proteomes remain uncharted. We hypothesized that wood-decaying fungi would possess promiscuous enzymes for detoxifying antifungal phytochemicals remaining in the dead plant bodies, which can be useful biocatalysts. We designed a computational mass spectrometry-based untargeted metabolomics pipeline for the phenotyping of biotransformation and applied it to 264 fungal cultures supplemented with antifungal plant phenolics. The analysis identified the occurrence of diverse reactivities by the tested fungal species. Among those, we focused on O-xylosylation of multiple phenolics by one of the species tested, Lentinus brumalis. By integrating the metabolic phenotyping results with publicly available genome sequences and transcriptome analysis, a UDP-glycosyltransferase designated UGT66A1 was identified and validated as an enzyme catalyzing O-xylosylation with broad substrate specificity. We anticipate that our analytical workflow will accelerate the further characterization of fungal enzymes as promising biocatalysts.

Enantioselective conjugate addition of malonates to α,β-unsaturated aldehydes catalysed by 4-oxalocrotonate tautomerase

The enantioselective conjugate addition of malonates to α,β-unsaturated aldehydes catalysed by 4-oxalocrotonate tautomerase is described. High conversions, high enantioselectivities, and good isolation yields were achieved for a range of substrates. We further completed a four-step synthesis of the antidepressant (+)-femoxetine by utilizing this reaction and an enzymatic reductive amination reaction.

Biocatalytic decarboxylative Michael addition for synthesis of 1,4-benzoxazinone derivatives

The Candida antarctica lipase B (Novozym 435) is found to catalyze a novel decarboxylative Michael addition in vinylogous carbamate systems for the synthesis of 1,4-benzoxazinone derivatives. The reaction goes through Michael addition, ester hydrolysis and decarboxylation. A possible mechanism is suggested, with simultaneous lipase-catalyzed Michael addition and ester hydrolysis. The present methodology offers formation of complex products through multi-step reactions in a one pot process under mild and facile reaction conditions with moderate to high yields (51–90%) and no side product formation. The reaction seems to be is a great example of enzymatic promiscuity.

Design of Artificial Enzymes Bearing Several Active Centers: New Trends, Opportunities and Problems

Harnessing enzymes which possess several catalytic activities is a topic where intense research has been carried out, mainly coupled with the development of cascade reactions. This review tries to cover the different possibilities to reach this goal: enzymes with promiscuous activities, fusion enzymes, enzymes + metal catalysts (including metal nanoparticles or site-directed attached organometallic catalyst), enzymes bearing non-canonical amino acids + metal catalysts, design of enzymes bearing a second biological but artificial active center (plurizymes) by coupling enzyme modelling and directed mutagenesis and plurizymes that have been site directed modified in both or in just one active center with an irreversible inhibitor attached to an organometallic catalyst. Some examples of cascade reactions catalyzed by the enzymes bearing several catalytic activities are also described. Finally, some foreseen problems of the use of these multi-activity enzymes are described (mainly related to the balance of the catalytic activities, necessary in many instances, or the different operational stabilities of the different catalytic activities). The design of new multi-activity enzymes (e.g., plurizymes or modified plurizymes) seems to be a topic with unarguable interest, as this may link biological and non-biological activities to establish new combo-catalysis routes.

Stereoselective Promiscuous Reactions Catalyzed by Lipases

The ability of lipases to display activity beyond their physiological reactions, so-called "catalytic promiscuity", has gained increasing interest in the last two decades as an important tool for expanding the application of these enzymes in organic synthesis. Some lipases have been shown to be effective in catalyzing a variety of C-C bond formation reactions and most of the investigations have been directed to the optimization of the products yield through a careful tuning of the experimental parameters. Despite the fact that new stereogenic carbons are formed in many of the tested reactions, the target products have been often obtained in racemic form and examples of an efficient asymmetric induction by the used lipases are quite limited. The aim of this review, mainly focused on those lipase-catalyzed promiscuous reactions in which optically active products have been obtained, is to offer a current state of art together with a perspective in this field of asymmetric synthesis.

Biocatalytic Asymmetric Cyclopropanations via Enzyme-Bound Iminium Ion Intermediates

Cyclopropane rings are an important structural motif frequently found in many natural products and pharmaceuticals. Commonly, biocatalytic methodologies for the asymmetric synthesis of cyclopropanes rely on repurposed or artificial heme enzymes. Here, we engineered an unusual cofactor‐independent cyclopropanation enzyme based on a promiscuous tautomerase for the enantioselective synthesis of various cyclopropanes via the nucleophilic addition of diethyl 2‐chloromalonate to α,β‐unsaturated aldehydes. The engineered enzyme promotes formation of the two new carbon‐carbon bonds with excellent stereocontrol over both stereocenters, affording the desired cyclopropanes with high diastereo‐ and enantiopurity (d.r. up to 25:1; e.r. up to 99:1). Our results highlight the usefulness of promiscuous enzymes for expanding the biocatalytic repertoire for non‐natural reactions.

Combined Theoretical and Experimental Study to Unravel the Differences in Promiscuous Amidase Activity of Two Nonhomologous Enzymes

Convergent evolution has resulted in nonhomologous enzymes that contain similar active sites that catalyze the same primary and secondary reactions. Comparing how these enzymes achieve their reaction promiscuity can yield valuable insights to develop functions from the optimization of latent activities. In this work, we have focused on the promiscuous amidase activity in the esterase from Bacillus subtilis (Bs2) and compared with the same activity in the promiscuous lipase B from Candida antarctica (CALB). The study, combining multiscale quantum mechanics/molecular mechanics (QM/MM) simulations, deep machine learning approaches, and experimental characterization of Bs2 kinetics, confirms the amidase activity of Bs2 and CALB. The computational results indicate that both enzymes offer a slightly different reaction environment reflected by electrostatic effects within the active site, thus resulting in a different reaction mechanism during the acylation step. A convolutional neural network (CNN) has been used to understand the conserved amino acids among the evolved protein family and suggest that Bs2 provides a more robust protein scaffold to perform future mutagenesis studies. Results derived from this work will help reveal the origin of enzyme promiscuity, which will find applications in enzyme (re)design, particularly in creating a highly active amidase.

Immobilization of Pseudomonas stutzeri lipase through Cross-linking Aggregates (CLEA) for reactions in Deep Eutectic Solvents

The use of deep eutectic solvents (DES) with buffer as cosolvent (up to 10 % v/v) leads to low-viscous media in which lipases can perform synthetic reactions, instead of hydrolysis. This paper explores the immobilization of Pseudomonas stutzeri lipase (TL) in cross-linking aggregates (CLEA) to deliver robust derivatives that are active in media like choline chloride - glycerol DES with buffer as cosolvent. While the free TL enzyme was markedly inactive in these media, TL-CLEA derivatives perform esterifications and can be reused several times. Overall, results are consistent with previous experiments reported for other lipases in these DES-water media and confirm that CLEA immobilization turns out a very useful and straightforward alternative for generating active (bio)catalysts for DES-aqueous media systems. Immobilized systems open the possibility of performing continuous processes in low-viscous DES-buffer media.

Intramolecular Stereoselective Stetter Reaction Catalyzed by Benzaldehyde Lyase

The reliable design and prediction of enzyme promiscuity to access transformations not observed in nature remains a long-standing challenge. Herein, we present the first example of an intramolecular stereoselective Stetter reaction catalyzed by benzaldehyde lyase, guided by the rational structure screening of various ThDP-dependent enzymes using molecular dynamics (MD) simulations. After optimization, high productivity (up to 99 %) and stereoselectivity (up to 99:1 e.r.) for this novel enzyme function was achieved.

Curating a comprehensive set of enzymatic reaction rules for efficient novel biosynthetic pathway design

Enzyme substrate promiscuity has significant implications for metabolic engineering. The ability to predict the space of possible enzymatic side reactions is crucial for elucidating underground metabolic networks in microorganisms, as well as harnessing novel biosynthetic capabilities of enzymes to produce desired chemicals. Reaction rule-based cheminformatics platforms have been implemented to computationally enumerate possible promiscuous reactions, relying on existing knowledge of enzymatic transformations to inform novel reactions. However, past versions of curated reaction rules have been limited by a lack of comprehensiveness in representing all possible transformations, as well as the need to prune rules to enhance computational efficiency in pathway expansion. To this end, we curated a set of 1224 most generalized reaction rules, automatically abstracted from atom-mapped MetaCyc reactions and verified to uniquely cover all common enzymatic transformations. We developed a framework to systematically identify and correct redundancies and errors in the curation process, resulting in a minimal, yet comprehensive, rule set. These reaction rules were capable of reproducing more than 85% of all reactions in the KEGG and BRENDA databases, for which a large fraction of reactions is not present in MetaCyc. Our rules exceed all previously published rule sets for which reproduction was possible in this coverage analysis, which allows for the exploration of a larger space of known enzymatic transformations. By leveraging the entire knowledge of possible metabolic reactions through generalized enzymatic reaction rules, we are able to better utilize underground metabolic pathways and accelerate novel biosynthetic pathway design to enable bioproduction towards a wider range of new molecules.

Generation of Oxidoreductases with Dual Alcohol Dehydrogenase and Amine Dehydrogenase Activity

The l-lysine-ϵ-dehydrogenase (LysEDH) from Geobacillus stearothermophilus naturally catalyzes the oxidative deamination of the ϵ-amino group of l-lysine. We previously engineered this enzyme to create amine dehydrogenase (AmDH) variants that possess a new hydrophobic cavity in their active site such that aromatic ketones can bind and be converted into α-chiral amines with excellent enantioselectivity. We also recently observed that LysEDH was capable of reducing aromatic aldehydes into primary alcohols. Herein, we harnessed the promiscuous alcohol dehydrogenase (ADH) activity of LysEDH to create new variants that exhibited enhanced catalytic activity for the reduction of substituted benzaldehydes and arylaliphatic aldehydes to primary alcohols. Notably, these novel engineered dehydrogenases also catalyzed the reductive amination of a variety of aldehydes and ketones with excellent enantioselectivity, thus exhibiting a dual AmDH/ADH activity. We envisioned that the catalytic bi-functionality of these enzymes could be applied for the direct conversion of alcohols into amines. As a proof-of-principle, we performed an unprecedented one-pot "hydrogen-borrowing" cascade to convert benzyl alcohol to benzylamine using a single enzyme. Conducting the same biocatalytic cascade in the presence of cofactor recycling enzymes (i.e., NADH-oxidase and formate dehydrogenase) increased the reaction yields. In summary, this work provides the first examples of enzymes showing "alcohol aminase" activity.

C=C-Ene-Reductases Reduce the C=N Bond of Oximes

Although enzymes have been found for many reactions, there are still transformations for which no enzyme is known. For instance, not a single defined enzyme has been described for the reduction of the C=N bond of an oxime, only whole organisms. Such an enzymatic reduction of an oxime may give access to (chiral) amines. By serendipity, we found that the oxime moiety adjacent to a ketone as well as an ester group can be reduced by ene-reductases (ERs) to an intermediate amino group. ERs are well-known enzymes for the reduction of activated alkenes, as of α,β-unsaturated ketones. For the specific substrate used here, the amine intermediate spontaneously reacts further to tetrasubstituted pyrazines. This reduction reaction represents an unexpected promiscuous activity of ERs expanding the toolkit of transformations using enzymes.

Chemistry, Sustainability and Naturality of Perfumery Biotech Ingredients

White biotechnology has emerged in biochemical manufacturing processes to deliver perfumery ingredients satisfying interests of the society for natural, eco-responsible, and sustainable materials. As a result, an intense R&D activity has taken place on these subjects, resulting in both scientific publications and patent applications reporting combinations of state-of-the-art approaches in biocatalysis, metabolic engineering, synthetic biology, biosynthesis elucidation, gene edition and cloning, and analytical chemistry. In this Minireview, a smelly selection of novel biotechnological processes and ingredients from a scientific articles and patents survey covering the last 6 years is presented and analysed in terms of chemistry, sustainability and naturality. Classification has been made between metabolic engineering on one side, allowing either biotechnological synthesis of essential oil surrogates or single molecule ingredients, and on the other side the optimisation of properties of natural complex substances by specific and selective enzymatic modifications of their chemical composition.

Protein promiscuity in drug discovery, drug-repurposing and antibiotic resistance

Proteins are supposed to bind to their substrates/ligands in a specific manner via their pre-formed binding sites, according to classical biochemistry. In recent years, several types of deviations from this norm have been observed and called promiscuous behavior. Enzymatic promiscuities allow several biochemical functions to be carried out by the same enzyme. The promiscuous activity can also be the origin of "new proteins" via gene duplication. In more recent years, proteins from prokaryotes, eukaryotes and viruses have been found to have intrinsic disorder and lack a preformed binding site. Intrinsic disorder is exploited in regulatory proteins such as those that are involved in transcription and signal transduction. Such proteins function by folding locally while binding to their ligands or interacting with other proteins. These phenomena have also been classified as examples of protein promiscuity and encompass diverse kinds of ligands that can bind to a protein. Given the significant extent of structural homology in many protein families, it is not surprising that ligands also have been found to display promiscuity. Promiscuous behavior of proteins offers both challenges and opportunities to the drug discovery programs such as drug repurposing. Pathogens when exposed to antibiotics exploit protein promiscuity in several ways to develop resistance to the drug. There is increasing evidence now to support that the disorder in proteins is a major tool used by pathogens for virulence and evade drug action by exploiting protein promiscuity. This review provides a holistic view of this multi-faceted phenomenon called protein promiscuity.

The first enzyme-promoted addition of nitromethane to imines (aza-Henry reaction)

Enzyme catalytic promiscuity is the ability of a single enzyme active site to catalyze several chemical transformations, among them those which are different from natural. We have attempted to use this feature of enzymes in the nucleophilic addition of nitromethane to aldimines (the aza-Henry reaction) whose chemically catalyzed version leads to synthetically useful β-nitroamines. We succeded in obtaining for the first time the desired products in the yields up to 81%. The most efficient proved lipase TL (from Pseudomonas stutzeri) and oxynitrilase from Arabidopsis thaliana. However, all the reactions investigated were non-stereoselective.

Broadening the Scope of Biocatalysis in Sustainable Organic Synthesis

This Review is aimed at synthetic organic chemists who may be familiar with organometallic catalysis but have no experience with biocatalysis, and seeks to provide an answer to the perennial question: if it is so attractive, why wasn't it extensively used in the past? The development of biocatalysis in industrial organic synthesis is traced from the middle of the last century. Advances in molecular biology in the last two decades, in particular genome sequencing, gene synthesis and directed evolution of proteins, have enabled remarkable improvements in scope and substantially reduced biocatalyst development times and cost contributions. Additionally, improvements in biocatalyst recovery and reuse have been facilitated by developments in enzyme immobilization technologies. Biocatalysis has become eminently competitive with chemocatalysis and the biocatalytic production of important pharmaceutical intermediates, such as enantiopure alcohols and amines, has become mainstream organic synthesis. The synthetic space of biocatalysis has significantly expanded and is currently being extended even further to include new-to-nature biocatalytic reactions.

Metabolic In Silico Network Expansions to Predict and Exploit Enzyme Promiscuity

There is a growing consensus that enzymes are capable of catalyzing not just one canonical reaction but entire families of related reactions. These capacities often go unnoticed in the enzyme's native context but can become apparent in engineered metabolism when the enzyme is exposed to novel substrates or high concentrations of pathway intermediates. This chapter describes how to use metabolic in silico network expansion (MINE) databases to predict novel biotransformations and their resulting metabolites. In particular, searching MINEs by structural similarity or with metabolomics data allows scientists to detect, exploit, or avoid these predicted transformations.

Mechanistic Insight into the Catalytic Promiscuity of Amine Dehydrogenases: Asymmetric Synthesis of Secondary and Primary Amines

Biocatalytic asymmetric amination of ketones, by using amine dehydrogenases (AmDHs) or transaminases, is an efficient method for the synthesis of α-chiral primary amines. A major challenge is to extend amination to the synthesis of secondary and tertiary amines. Herein, for the first time, it is shown that AmDHs are capable of accepting other amine donors, thus giving access to enantioenriched secondary amines with conversions up to 43 %. Surprisingly, in several cases, the promiscuous formation of enantiopure primary amines, along with the expected secondary amines, was observed. By conducting practical laboratory experiments and computational experiments, it is proposed that the promiscuous formation of primary amines along with secondary amines is due to an unprecedented nicotinamide (NAD)-dependent formal transamination catalysed by AmDHs. In nature, this type of mechanism is commonly performed by pyridoxal 5'-phosphate aminotransferase and not by dehydrogenases. Finally, a catalytic pathway that rationalises the promiscuous NAD-dependent formal transamination activity and explains the formation of the observed mixture of products is proposed. This work increases the understanding of the catalytic mechanism of NAD-dependent aminating enzymes, such as AmDHs, and will aid further research into the rational engineering of oxidoreductases for the synthesis of α-chiral secondary and tertiary amines.

Diastereoselective synthesis of bis(α-aminophosphonates) by lipase catalytic promiscuity

New bis(α-aminophosphonates) were directly prepared with high diastereoselectivity by lipase catalytic promiscuity in the presence of immobilized Candida antarctica lipase.

Concurrent Asymmetric Reactions Combining Photocatalysis and Enzyme Catalysis: Direct Enantioselective Synthesis of 2,2-Disubstituted Indol-3-ones from 2-Arylindoles

The combination of photoredox and enzymatic catalysis for the direct asymmetric one-pot synthesis of 2,2-disubstituted indol-3-ones from 2-arylindoles through concurrent oxidization and alkylation reactions is described. 2-Arylindoles can be photocatalytically oxidized to 2-arylindol-3-one with subsequent enantioselective alkylation with ketones catalyzed by wheat germ lipase (WGL). The chiral quaternary carbon center at C2 of the indoles was directly constructed. This mode of concurrent photobiocatalysis provides a mild and powerful strategy for one-pot enantioselective synthesis of complex compounds. The experiments proved that other lipases containing structurally analogous catalytic triad in the active site also can catalyze the reaction in the same way. This reaction is the first example of combining the non-natural catalytic activity of hydrolases with visible-light catalysis for enantioselective organic synthesis and it does not require any cofactors.

Catalytic Promiscuity of Galactose Oxidase: A Mild Synthesis of Nitriles from Alcohols, Air, and Ammonia

We report an unprecedented catalytically promiscuous activity of the copper-dependent enzyme galactose oxidase. The enzyme catalyses the one-pot conversion of alcohols into the related nitriles under mild reaction conditions in ammonium buffer, consuming ammonia as the source of nitrogen and dioxygen (from air at atmospheric pressure) as the only oxidant. Thus, this green method does not require either cyanide salts, toxic metals, or undesired oxidants in stoichiometric amounts. The substrate scope of the reaction includes benzyl and cinnamyl alcohols as well as 4- and 3-pyridylmethanol, giving access to valuable chemical compounds. The oxidation proceeds through oxidation from alcohol to aldehyde, in situ imine formation, and final direct oxidation to nitrile.

The limits to biocatalysis: pushing the envelope

In the period 1985 to 1995 applications of biocatalysis, driven by the need for more sustainable manufacture of chemicals and catalytic, (enantio)selective methods for the synthesis of pharmaceutical intermediates, largely involved the available hydrolases. This was followed, in the next two decades, by revolutionary developments in protein engineering and directed evolution for the optimisation of enzyme function and performance that totally changed the biocatalysis landscape. In the same period, metabolic engineering and synthetic biology revolutionised the use of whole cell biocatalysis in the synthesis of commodity chemicals by fermentation. In particular, developments in the enzymatic enantioselective synthesis of chiral alcohols and amines are highlighted. Progress in enzyme immobilisation facilitated applications under harsh industrial conditions, such as in organic solvents. The emergence of biocatalytic or chemoenzymatic cascade processes, often with co-immobilised enzymes, has enabled telescoping of multi-step processes. Discovering and inventing new biocatalytic processes, based on (meta)genomic sequencing, evolving enzyme promiscuity, chemomimetic biocatalysis, artificial metalloenzymes, and the introduction of non-canonical amino acids into proteins, are pushing back the limits of biocatalysis function. Finally, the integral role of biocatalysis in developing a biobased carbon-neutral economy is discussed.

Catalytic promiscuity enabled by photoredox catalysis in nicotinamide-dependent oxidoreductases

Strategies that provide enzymes with the ability to catalyse non-natural reactions are of considerable synthetic value. Photoredox catalysis has proved adept at expanding the synthetic repertoire of existing catalytic platforms, yet, in the realm of biocatalysis it has primarily been used for cofactor regeneration. Here we show that photoredox catalysts can be used to enable new catalytic function in nicotinamide-dependent enzymes. Under visible-light irradiation, xanthene-based photocatalysts enable a double-bond reductase to catalyse an enantioselective deacetoxylation. Mechanistic experiments support the intermediacy of an α-acyl radical, formed after the elimination of acetate. Isotopic labelling experiments support nicotinamide as the source of the hydrogen atom. Preliminary calculations and mechanistic experiments suggest that binding to the protein attenuates the reduction potential of the starting material, an important feature for localizing radical formation to the enzyme active site. The generality of this approach is highlighted with the radical dehalogenation of α-bromoamides catalysed by ketoreductases with Eosin Y as a photocatalyst.

Engineering substrate promiscuity in 2,4-dichlorophenol hydroxylase by in silico design

2,4-Dichlorophenol hydroxylase (2,4-DCP hydroxylase) is a key enzyme in the degradation of 2,4-dichlorophenoxyacetic acid in the hydroxylation step in many bacteria. Our previous study demonstrated that a 2,4-DCP hydroxylase (TfdB-JLU) exhibits broad substrate specificity for chlorophenols (CPs) and their homologues. In this study, TfdB-JLU has been engineered by rational design to further broaden its substrate scope towards CPs. We dissect the architectures of enzymes from oxidoreductase families to discover their underlying structural sources of substrate promiscuity. A homology model of TfdB-JLU has been built and docking experiments of this homology model with its natural substrate 2,4-DCP reveal that the phenyl rings of 2,4-DCP form strong interactions with residues His47, Ile48, Trp222, Pro316, and Phe424. These residues are found to be important for substrate binding in the active site. Then, the site-directed mutagenesis strategy has been applied for redesigning substrate promiscuity in TfdB-JLU. The TfdB-JLU-P316Q variant obtained shows a significant enhancement of activity (up to 3.4-fold) toward 10 CP congeners compared to wild-type TfdB-JLU. Interestingly, the active improvements of TfdB-JLU-P316Q toward CP congeners show significant difference, especially for active improvements of positional congeners such as 3-CP (1.1-fold) compared to 4-CP (3.0-fold), as well as 2,3-DCP (1.2-fold) compared to 2,5-DCP (3.4-fold). Structural analysis results indicate that the improvement in substrate promiscuity of the variant enzyme compared to the wild-type enzyme is possibly due to the increase of non-bonding interaction. The results suggest that exploiting enzyme-substrate promiscuity is promising, which would provide a starting point for designing and engineering novel biological catalysts for pollution removal.