Special Issue "Asymmetric and Selective Biocatalysis"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (31 October 2016)

Special Issue Editors

Guest Editor
Prof. Dr. Jose M. Palomo

Departament of Biocatalysis, Institute of Catalysis (ICP-CSIC), Marie Curie 2, Cantoblanco, Campus UAM, 28049 Madrid, Spain
Website | E-Mail
Interests: biotransformations; catalysis; carbohydrate chemistry; medicinal chemistry
Guest Editor
Prof. Dr. Cesar Mateo

Group of Chemical Processes Catalyzed by Enzymes, Departament of Biocatalysis, Institute of Catalysis (ICP-CSIC), Marie Curie 2, Cantoblanco, Campus UAM, 28049 Madrid, Spain
Website | E-Mail
Interests: enzyme processes; biocatalysis; CO2 transformation; red-ox processes; enzyme immobilization

Special Issue Information

Dear Colleagues,

The preparation of pure chiral building blocks with the desired configuration is extremely important in different areas, especially in the production of pharmaceuticals. In this way, biocatalysts (cells, enzymes, catalytic antibodies, or ribozymes) represent the best alternative to the chemical processes because of the high regio- and enantio-selectivity towards different substrates at very mild conditions.

This Special Issue will be focused on innovative and novel research in “Asymmetric and Selective Biotransformations”.

Prof. Dr. Jose M. Palomo
Prof. Dr. Cesar Mateo
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • kinetic resolutions of racemic mixtures
  • asymmetric synthesis
  • oxidations
  • reductions
  • C-C bonding formation
  • regioselectivity
  • enantioselectivity

Published Papers (9 papers)

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Research

Jump to: Review

Open AccessFeature PaperCommunication Stereoselective Chemoenzymatic Synthesis of Optically Active Aryl-Substituted Oxygen-Containing Heterocycles
Catalysts 2017, 7(2), 37; doi:10.3390/catal7020037
Received: 22 December 2016 / Revised: 16 January 2017 / Accepted: 17 January 2017 / Published: 25 January 2017
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Abstract
A two-step stereoselective chemoenzymatic synthesis of optically active α-aryl-substituted oxygen heterocycles was developed, exploiting a whole-cell mediated asymmetric reduction of α-, β-, and γ-chloroalkyl arylketones followed by a stereospecific cyclization of the corresponding chlorohydrins into the target heterocycles. Among the various whole cells
[...] Read more.
A two-step stereoselective chemoenzymatic synthesis of optically active α-aryl-substituted oxygen heterocycles was developed, exploiting a whole-cell mediated asymmetric reduction of α-, β-, and γ-chloroalkyl arylketones followed by a stereospecific cyclization of the corresponding chlorohydrins into the target heterocycles. Among the various whole cells screened (baker’s yeast, Kluyveromyces marxianus CBS 6556, Saccharomyces cerevisiae CBS 7336, Lactobacillus reuteri DSM 20016), baker’s yeast was the one providing the best yields and the highest enantiomeric ratios (up to 95:5 er) in the bioreduction of the above ketones. The obtained optically active chlorohydrins could be almost quantitatively cyclized in a basic medium into the corresponding α-aryl-substituted cyclic ethers without any erosion of their enantiomeric integrity. In this respect, valuable, chiral non-racemic functionalized oxygen containing heterocycles (e.g., (S)-styrene oxide, (S)-2-phenyloxetane, (S)-2-phenyltetrahydrofuran), amenable to be further elaborated on, can be smoothly and successfully generated from their prochiral precursors. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessArticle N-acetylglucosamine 2-Epimerase from Pedobacter heparinus: First Experimental Evidence of a Deprotonation/Reprotonation Mechanism
Catalysts 2016, 6(12), 212; doi:10.3390/catal6120212
Received: 26 November 2016 / Revised: 11 December 2016 / Accepted: 12 December 2016 / Published: 17 December 2016
Cited by 3 | PDF Full-text (2675 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The control of cellular N-acetylmannosamine (ManNAc) levels has been postulated to be an effective way to modulate the decoration of cell surfaces with sialic acid. N-acetylglucosamine 2-epimerase catalyzes the interconversion of N-acetylglucosamine (GlcNAc) and ManNAc. Herein, we describe the cloning,
[...] Read more.
The control of cellular N-acetylmannosamine (ManNAc) levels has been postulated to be an effective way to modulate the decoration of cell surfaces with sialic acid. N-acetylglucosamine 2-epimerase catalyzes the interconversion of N-acetylglucosamine (GlcNAc) and ManNAc. Herein, we describe the cloning, expression, purification and biochemical characterization of an unstudied N-acetylglucosamine 2-epimerase from Pedobacter heparinus (PhGn2E). To further characterize the enzyme, several N-acylated glucosamine derivatives were chemically synthesized, and subsequently used to test the substrate specificity of PhGn2E. Furthermore, NMR studies of deuterium/hydrogen exchange at the anomeric hydroxy group and C-2 positions of the substrate in the reaction mixture confirmed for the first time the postulated epimerization reaction via ring-opening/enolate formation. Site-directed mutagenesis of key residues in the active site showed that Arg63 and Glu314 are directly involved in proton abstraction and re-incorporation onto the substrate. As all mechanistically relevant active site residues also occur in all mammalian isoforms, PhGn2E can serve as a model N-acetylglucosamine 2-epimerase for further elucidation of the active site mechanism in these enzymes. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessArticle Photoassisted Oxidation of Sulfides Catalyzed by Artificial Metalloenzymes Using Water as an Oxygen Source
Catalysts 2016, 6(12), 202; doi:10.3390/catal6120202
Received: 19 October 2016 / Revised: 24 November 2016 / Accepted: 6 December 2016 / Published: 12 December 2016
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Abstract
The Mn(TpCPP)-Xln10A artificial metalloenzyme, obtained by non-covalent insertion of Mn(III)-meso-tetrakis(p-carboxyphenyl)porphyrin [Mn(TpCPP), 1-Mn] into xylanase 10A from Streptomyces lividans (Xln10A) as a host protein, was found able to catalyze the selective photo-induced oxidation of organic substrates in the presence of [Ru
[...] Read more.
The Mn(TpCPP)-Xln10A artificial metalloenzyme, obtained by non-covalent insertion of Mn(III)-meso-tetrakis(p-carboxyphenyl)porphyrin [Mn(TpCPP), 1-Mn] into xylanase 10A from Streptomyces lividans (Xln10A) as a host protein, was found able to catalyze the selective photo-induced oxidation of organic substrates in the presence of [RuII(bpy)3]2+ as a photosensitizer and [CoIII(NH3)5Cl]2+ as a sacrificial electron acceptor, using water as oxygen atom source. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessArticle Mechanistic and Structural Insight to an Evolved Benzoylformate Decarboxylase with Enhanced Pyruvate Decarboxylase Activity
Catalysts 2016, 6(12), 190; doi:10.3390/catal6120190
Received: 1 November 2016 / Revised: 25 November 2016 / Accepted: 28 November 2016 / Published: 30 November 2016
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Abstract
Benzoylformate decarboxylase (BFDC) and pyruvate decarboxylase (PDC) are thiamin diphosphate-dependent enzymes that share some structural and mechanistic similarities. Both enzymes catalyze the nonoxidative decarboxylation of 2-keto acids, yet differ considerably in their substrate specificity. In particular, the BFDC from P. putida exhibits very
[...] Read more.
Benzoylformate decarboxylase (BFDC) and pyruvate decarboxylase (PDC) are thiamin diphosphate-dependent enzymes that share some structural and mechanistic similarities. Both enzymes catalyze the nonoxidative decarboxylation of 2-keto acids, yet differ considerably in their substrate specificity. In particular, the BFDC from P. putida exhibits very limited activity with pyruvate, whereas the PDCs from S. cerevisiae or from Z. mobilis show virtually no activity with benzoylformate (phenylglyoxylate). Previously, saturation mutagenesis was used to generate the BFDC T377L/A460Y variant, which exhibited a greater than 10,000-fold increase in pyruvate/benzoylformate substrate utilization ratio compared to that of wtBFDC. Much of this change could be attributed to an improvement in the Km value for pyruvate and, concomitantly, a decrease in the kcat value for benzoylformate. However, the steady-state data did not provide any details about changes in individual catalytic steps. To gain insight into the changes in conversion rates of pyruvate and benzoylformate to acetaldehyde and benzaldehyde, respectively, by the BFDC T377L/A460Y variant, reaction intermediates of both substrates were analyzed by NMR and microscopic rate constants for the elementary catalytic steps were calculated. Herein we also report the high resolution X-ray structure of the BFDC T377L/A460Y variant, which provides context for the observed changes in substrate specificity. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessFeature PaperArticle New Tailor-Made Alkyl-Aldehyde Bifunctional Supports for Lipase Immobilization
Catalysts 2016, 6(12), 191; doi:10.3390/catal6120191
Received: 28 October 2016 / Revised: 24 November 2016 / Accepted: 27 November 2016 / Published: 30 November 2016
Cited by 3 | PDF Full-text (1643 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Immobilized and stabilized lipases are important biocatalytic tools. In this paper, different tailor-made bifunctional supports were prepared for the immobilization of a new metagenomic lipase (LipC12). The new supports contained hydrophobic groups (different alkyl groups) to promote interfacial adsorption of the lipase and
[...] Read more.
Immobilized and stabilized lipases are important biocatalytic tools. In this paper, different tailor-made bifunctional supports were prepared for the immobilization of a new metagenomic lipase (LipC12). The new supports contained hydrophobic groups (different alkyl groups) to promote interfacial adsorption of the lipase and aldehyde groups to react covalently with the amino groups of side chains of the adsorbed lipase. The best catalyst was 3.5-fold more active and 5000-fold more stable than the soluble enzyme. It was successfully used in the regioselective deacetylation of peracetylated d-glucal. The PEGylated immobilized lipase showed high regioselectivity, producing high yields of the C-3 monodeacetylated product at pH 5.0 and 4 °C. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessArticle Efficient Production of Enantiopure d-Lysine from l-Lysine by a Two-Enzyme Cascade System
Catalysts 2016, 6(11), 168; doi:10.3390/catal6110168
Received: 24 September 2016 / Revised: 23 October 2016 / Accepted: 25 October 2016 / Published: 30 October 2016
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Abstract
The microbial production of d-lysine has been of great interest as a medicinal raw material. Here, a two-step process for d-lysine production from l-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase was developed. The
[...] Read more.
The microbial production of d-lysine has been of great interest as a medicinal raw material. Here, a two-step process for d-lysine production from l-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase was developed. The whole-cell activities of engineered Escherichia coli expressing racemases from the strains Proteus mirabilis (LYR) and Lactobacillus paracasei (AAR) were first investigated comparatively. When the strain BL21-LYR with higher racemization activity was employed, l-lysine was rapidly racemized to give dl-lysine, and the d-lysine yield was approximately 48% after 0.5 h. Next, l-lysine was selectively catabolized to generate cadaverine by lysine decarboxylase. The comparative analysis of the decarboxylation activities of resting whole cells, permeabilized cells, and crude enzyme revealed that the crude enzyme was the best biocatalyst for enantiopure d-lysine production. The reaction temperature, pH, metal ion additive, and pyridoxal 5′-phosphate content of this two-step production process were subsequently optimized. Under optimal conditions, 750.7 mmol/L d-lysine was finally obtained from 1710 mmol/L l-lysine after 1 h of racemization reaction and 0.5 h of decarboxylation reaction. d-lysine yield could reach 48.8% with enantiomeric excess (ee) ≥ 99%. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessFeature PaperArticle Covalent Immobilization of Candida rugosa Lipase at Alkaline pH and Their Application in the Regioselective Deprotection of Per-O-acetylated Thymidine
Catalysts 2016, 6(8), 115; doi:10.3390/catal6080115
Received: 10 June 2016 / Revised: 15 July 2016 / Accepted: 27 July 2016 / Published: 2 August 2016
Cited by 7 | PDF Full-text (3441 KB) | HTML Full-text | XML Full-text
Abstract
Lipase from Candida rugosa (CRL) was stabilized at alkaline pH to overcome the inactivation problem and was immobilized for the first time by multipoint covalent attachment on different aldehyde-activated matrices. PEG was used as a stabilizing agent on the activity of CRL. At
[...] Read more.
Lipase from Candida rugosa (CRL) was stabilized at alkaline pH to overcome the inactivation problem and was immobilized for the first time by multipoint covalent attachment on different aldehyde-activated matrices. PEG was used as a stabilizing agent on the activity of CRL. At these conditions, CRL maintained 50% activity at pH 10 after 17 h incubation in the presence of 40% (w/v) of PEG, whereas the enzyme without additive was instantaneously inactive after incubation at pH 10. Thus, this enzyme was covalently immobilized at alkaline pH on three aldehyde-activated supports: aldehyde-activated Sepharose, aldehyde-activated Lewatit105 and heterofunctional aldehyde-activated EDA-Sepharose in high overall yields. Heterogeneous stable CRL catalysts at high temperature and solvent were obtained. The aldehyde-activated Sepharose-CRL preparation maintained 70% activity at 50 °C or 30% (v/v) acetonitrile after 22 h and exhibited high regioselectivity in the deprotection process of per-O-acetylated thymidine, producing the 3′-OH-5′-OAc-thymidine in 91% yield at pH 5. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Review

Jump to: Research

Open AccessReview Old Yellow Enzyme-Catalysed Asymmetric Hydrogenation: Linking Family Roots with Improved Catalysis
Catalysts 2017, 7(5), 130; doi:10.3390/catal7050130
Received: 16 March 2017 / Revised: 17 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
Cited by 1 | PDF Full-text (5815 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Asymmetric hydrogenation of activated alkenes catalysed by ene-reductases from the old yellow enzyme family (OYEs) leading to chiral products is of potential interest for industrial processes. OYEs’ dependency on the pyridine nucleotide coenzyme can be circumvented through established artificial hydride donors such as
[...] Read more.
Asymmetric hydrogenation of activated alkenes catalysed by ene-reductases from the old yellow enzyme family (OYEs) leading to chiral products is of potential interest for industrial processes. OYEs’ dependency on the pyridine nucleotide coenzyme can be circumvented through established artificial hydride donors such as nicotinamide coenzyme biomimetics (NCBs). Several OYEs were found to exhibit higher reduction rates with NCBs. In this review, we describe a new classification of OYEs into three main classes by phylogenetic and structural analysis of characterized OYEs. The family roots are linked with their use as chiral catalysts and their mode of action with NCBs. The link between bioinformatics (sequence analysis), biochemistry (structure–function analysis), and biocatalysis (conversion, enantioselectivity and kinetics) can enable an early classification of a putative ene-reductase and therefore the indication of the binding mode of various activated alkenes. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessFeature PaperReview Tandem Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis
Catalysts 2016, 6(12), 194; doi:10.3390/catal6120194
Received: 7 November 2016 / Revised: 28 November 2016 / Accepted: 29 November 2016 / Published: 5 December 2016
Cited by 2 | PDF Full-text (6342 KB) | HTML Full-text | XML Full-text
Abstract
The application of biocatalysts in the synthesis of fine chemicals and medicinal compounds has grown significantly in recent years. Particularly, there is a growing interest in the development of one-pot tandem catalytic systems combining the reactivity of a chemical catalyst with the selectivity
[...] Read more.
The application of biocatalysts in the synthesis of fine chemicals and medicinal compounds has grown significantly in recent years. Particularly, there is a growing interest in the development of one-pot tandem catalytic systems combining the reactivity of a chemical catalyst with the selectivity engendered by the active site of an enzyme. Such tandem catalytic systems can achieve levels of chemo-, regio-, and stereo-selectivities that are unattainable with a small molecule catalyst. In addition, artificial metalloenzymes widen the range of reactivities and catalyzed reactions that are potentially employable. This review highlights some of the recent examples in the past three years that combined transition metal catalysis with enzymatic catalysis. This field is still in its infancy. However, with recent advances in protein engineering, catalyst synthesis, artificial metalloenzymes and supramolecular assembly, there is great potential to develop more sophisticated tandem chemoenzymatic processes for the synthesis of structurally complex chemicals. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Tandem Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis
Authors: Yajie Wang and Huimin Zhao,
Affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign.
Abstract: The application of biocatalysts in the synthesis of fine chemicals and medicinal compounds has grown significantly in recent years. Particularly, the development of either sequential or one-pot tandem catalytic system combining the reactivity of a chemical catalyst with the selectivity engendered by the active site of a protein has proved to be appealing since it can achieve levels of chemo-, regio-, and stereo- selectivity that are unattainable with a small molecule catalyst. Engineered or artificial metalloenzymes also widen the range of reactivities and catalyzed reactions that are potentially employable. This review presents some of the most recent (2013-2016) examples that combined transition metal catalysis with enzymatic catalysis.

Title: Evaluation of Sucrose Synthase and O-Glycosyltransferase Fusion Proteins
Authors: Griet Dewitte1,°, Margo Diricks1,°, Ophelia Gevaert1, Oliver Spadiut2 and Tom Desmet1,*
Affiliations: 1Ghent University, Centre for Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Coupure Links 653, B-9000 Ghent, Belgium
2 Vienna University of Technology, Institute of Chemical Engineering, Research Area Biochemical Engineering, Gumpendorfer Strasse 1a, A-1060 Vienna, Austria
°These authors contributed equally to this work
*Correspondence: tom.desmet@ugent.be; Tel.: +32-9-264-9920
Abstract: Glucosyltransferases are effective biocatalysts for the glucosylation of small compounds such as polyphenols. However, their preparative application requires efficient methods to generate expensive UDP-sugar donors. Interestingly, sucrose synthases catalyse the conversion of cheap sucrose into UDP-sugars. Here, we describe the in-frame fusion between a mutant sucrose synthase from Acidithiobacillus caldus (SuSy) and a promiscuous glycosyltransferase from Stevia rebaudiana (UGT). Variation of linker and order of this bacterial-plant fusion protein yielded three bifunctional enzymes exhibiting increased enzymatic activities when compared to native UGT and SuSy. In this way, the cost-efficient and selective glucosylation of the anti-oxidant catechin was enabled.
Keywords: biocatalyst; glycosylation; fusion; protein

Title: Old Yellow Enzyme-catalysed asymmetric hydrogenation with cofactor analogues: a journey to find family roots
Authors: Caroline Paul and Dirk Tischler
Abstract: Asymmetric hydrogenation of activated alkenes by Old Yellow Enzymes (OYEs) has a significant interest in industrial processes. The dependency of OYEs on the nicotinamide coenzyme can now be circumvented by established recycling systems, or even better, with the recently reported nicotinamide coenzyme biomimetics (NCBs). Certain OYEs were found to exhibit higher catalytic activity with several NCB analogues. In this review we classify OYE families according to various parameters and relate their activity data with the current NCBs.

Title: Hydrolysis vs. Aminolysis: Directed Optimization of Both Activities via Phage Display and Covalent Acyl-Enzyme Selection
Authors: Sabrina Gissel1, Sandra Liebscher1, Li Yuan2, Sven Pfeifer2, Christoph Meyer1,3, Lars Franke1, Bianka Hartrodt1, and Frank Bordusa1*
Affiliations:1Institute of Biochemistry/Biotechnology, Martin-Luther-University Halle/Wittenberg, Kurt-Mothes-Straße 3, D-06120 Halle/Saale (Germany)
2 Junior research group – artificial binding proteins, Heinrich-Damerow-Straße 4, D-06120 Halle/Saale (Germany)
3 Eucodis Bioscience GmbH Deutschland, Heinrich-Damerow-Straße 4, D-06120 Halle/Saale (Germany)
Abstract: This study establishes the Phage Display technology as suitable in vitro selection system for directed optimization of the previously designed trypsiligase used for the site-specific synthesis of antibody drug conjugates. In contrast to the conventional application of this evolutionary technology to improve typically the specificity or binding behavior of enzymes or proteins, focus was exclusively laid on the systematic reduction of the biocatalyst’s native secondary hydrolysis activity impairing the synthetic properties of the designed enzyme. For this purpose, an original selection approach based on the catalytic mechanism of trypsiligase was established using the covalent acyl-enzyme intermediate as novel pivot for the selection process. The general function of the approach was successfully validated in a first experimental trial entailing the identification of trypsiligase variants with specifically improved catalytic properties. The results led further assume that besides trypsiligase also the targeted engineering of other enzymes, which likewise generate acyl-enzyme intermediates during catalysis, should profit from the designed optimization approach.
Keywords: Phage Display, Evolution, Enzyme Engineering, Antibody-Drug-Conjugates, Hydrolases

Title: Regioselective chemoenzymatic syntheses of chromogenic substrates for feruloyl esterases
Authors: Olga Gherbovet 1, Fernando Ferreira 1, Mélanie Ragon 1, Julien Durand 1, Sophie Bozonnet 1, Michael J. O’Donohue 1 and Régis Fauré 1,*
Affiliation:1LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France
*Correspondence: regis.faure@insa-toulouse.fr; Tel.: +33-561-55-9488
Abstract: Although feruloyl esterases constitute an important sub-group of hydrolytic enzymes involved in the deconstruction of plant cell wall polysaccharides, their identification and detailed characterization are still challenging topics because of the availability of ad hoc substrates. In this respect, devoted chromogenic substrates are valuable tools to provide quick and easy detection of enzyme-mediated hydrolysis of the ester bond, which can be readily monitored through color change. Both new and commercially available ferulate derivatives were prepared by regioselective chemoenzymatic synthetic routes and their efficiency as substrates for type A feruloyl esterase from Aspergillus niger was evaluated. The synthetic pathways leading to indolyl, (chloro)nitrophenyl and 4-nitrocatechol O-5 feruloylated-α-L-arabinofuranosides were significantly shortened, and therefore corresponding overall yields enhanced, by using enzymatic transesterification of ferulic acid from its active vinyl ester form to the primary hydroxyl group of the α-L-arabinofuranosyl units with Lipolase 100T (from Thermomyces lanuginosus). Furthermore, feruloylated-butanetriol 4-nitrocatechol analog containing a cleavable linker arm instead of a carbohydrate moiety was also obtained in 12% overall yield in 4 steps, combining regioselective functionalization of 4NTC and enzymatic transesterification. The practical synthesis at preparative scale of this library of chromogenic probes makes easier further investigation of feruloyl esterases.
Keywords: biocatalysis; transesterification; screening; CAZymes; ferulic ester hydrolysis

Title: Efficient production of enantiopure D-lysine from L-lysine by lysine racemase and decarboxylase coupled system
Authors: Xin Wang, Li Yang, Weijia Cao, Hanxiao Ying, Kequan Chen*, Pingkai Ouyan
Affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu, China

 

Title: A General Strategy For Stereoselective Chemoenzymatic Synthesis Of Optically Active Aryl-Substituted Oxygen Heterocycles
Authors: Paola Vitale,* Antonia Digeo, Filippo Maria Perna, Gennaro Agrimi, Antonio Scilimati, Antonio Salomone, Cosimo Cardellicchio, and Vito Capriati*
Abstract:
We introduce a new and extremely efficient, general strategy for highly stereoselective chemoenzymatic synthesis of optically active α-aryl-substituted oxygen heterocycles. This is based on the biocatalytic asymmetric reduction of halogeno-aryl ketones run in the presence of whole cell biocatalysts,and followed by a stereospecific cyclization of the corresponding halohydrins into the target heterocycles. Some bench bioreduction processes catalyzed by different whole cells microorganisms (bakers' yeast, Kluyveromyces marxianus CBS 6556 and Saccharomyces cerevisiae CBS 7336, Lactobacillus reuteri DSM 20016) have been preliminarily screened in order to optimize the experimental conditions and to choose the more suitable biocatalyst. Among the tested biocatalysts, bakers' yeast was found to provide the best yields and the highest enantiomeric ratios (ers) in the bioreductions of α-, β-, and γ-chloro-aryl ketones. In the presence of tBuOK, the obtained optically active chlorohydrins could be quantitatively cyclized into the corresponding α-aryl-substituted cyclic ethers without erosion of the enantiomeric excess. In this way, valuable, chiral non-racemic functionalized oxygen heterocycles [e.g., (S)-styrene oxide, 98% yield, 91:9er; (S)-2- phenyloxetane, 98% yield, 99:1 er; (S)-2-phenyltetrahydrofuran, 98% yield, 93:7 er], amenable to be further elaborated, can be generated from prochiral precursors. Since the wild-type whole-cell biocatalyst selected (baker’s yeast) is cheap and commercially available, the discussed methodology is considered auspicious for setting up industrially relevant and cost-effective biotransformations for a large-scale production of oxygen heterocycles.

Title: Mechanistic and structural insight to an evolved benzoylformate decarboxylase with enhanced pyruvate decarboxylase activity
Authors: Michael J. McLeish, et al.
Affiliations: Department of Chemistry & Chemical Biology, Indiana University-Purdue University Indianapolis (IUPUI), 402 N. Blackford St. LD 326D, Indianapolis IN 46202
Abstract: Benzoylformate decarboxylase (BFDC) and pyruvate decarboxylase (PDC) are thiamin diphosphate-dependent enzymes that share some structural and mechanistic similarities. Both enzymes catalyze the nonoxidative decarboxylation of 2-keto acids, yet differ considerably in their substrate specificity. In particular, the BFDC from P. putida exhibits very limited activity with pyruvate, whereas the PDCs from S. cerevisiae or from Z. mobilis show virtually no activity with benzoylformate (phenylglyoxylate). Previously, saturation mutagenesis was used to generate the BFDC T377L/A460Y variant. This variant exhibited a greater than 10,000-fold increase in pyruvate/benzoylformate substrate utilization ratio compared to that of wtBFDC. Much of this change could be attributed to an improvement in the Km value for pyruvate and, concomitantly, a decrease in the kcat value for benzoylformate. However, the steady-state data did not provide any details about changes in individual catalytic steps. To gain insight into the changes in conversion rates of pyruvate and benzoylformate to acetaldehyde and benzaldehyde, respectively, by the BFDC T377L/A460Y variant, reaction intermediates of both substrates were analyzed by NMR and microscopic rate constants for the elementary catalytic steps were calculated. Herein we also report the high resolution X-ray structure of the BFDC T377L/A460Y variant, which helps to address the structural basis for the observed changes in substrate specificity.

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