Editorial

3 pages, 170 KiB

Open AccessEditorial

by Cesar Mateo and Jose M. Palomo

Catalysts 2018, 8(12), 588; https://doi.org/10.3390/catal8120588 - 28 Nov 2018

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The synthesis of compounds or chiral building-blocks with the desired configuration is one of the greatest challenges of chemistry and is of great interest in different fields such as analytical chemistry and especially in fine and pharmaceutical chemistry. [...] Full article

(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)

Research

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1316 KiB

Open AccessFeature PaperCommunication

Stereoselective Chemoenzymatic Synthesis of Optically Active Aryl-Substituted Oxygen-Containing Heterocycles

by Paola Vitale, Antonia Digeo, Filippo Maria Perna, Gennaro Agrimi, Antonio Salomone, Antonio Scilimati, Cosimo Cardellicchio and Vito Capriati

Catalysts 2017, 7(2), 37; https://doi.org/10.3390/catal7020037 - 25 Jan 2017

Cited by 11 | Viewed by 4775

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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2675 KiB

Open AccessArticle

N-acetylglucosamine 2-Epimerase from Pedobacter heparinus: First Experimental Evidence of a Deprotonation/Reprotonation Mechanism

by Su-Yan Wang, Pedro Laborda, Ai-Min Lu, Xu-Chu Duan, Hong-Yu Ma, Li Liu and Josef Voglmeir

Catalysts 2016, 6(12), 212; https://doi.org/10.3390/catal6120212 - 17 Dec 2016

Cited by 14 | Viewed by 8179

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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1566 KiB

Open AccessArticle

Photoassisted Oxidation of Sulfides Catalyzed by Artificial Metalloenzymes Using Water as an Oxygen Source

by Christian Herrero, Nhung Nguyen-Thi, Fabien Hammerer, Frédéric Banse, Donald Gagné, Nicolas Doucet, Jean-Pierre Mahy and Rémy Ricoux

Catalysts 2016, 6(12), 202; https://doi.org/10.3390/catal6120202 - 12 Dec 2016

Cited by 12 | Viewed by 6330

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 [Ru^II(bpy)₃]²⁺ as a photosensitizer and [Co^III(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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1643 KiB

Open AccessFeature PaperArticle

New Tailor-Made Alkyl-Aldehyde Bifunctional Supports for Lipase Immobilization

by Robson Carlos Alnoch, Ricardo Rodrigues de Melo, Jose M. Palomo, Emanuel Maltempi de Souza, Nadia Krieger and Cesar Mateo

Catalysts 2016, 6(12), 191; https://doi.org/10.3390/catal6120191 - 30 Nov 2016

Cited by 14 | Viewed by 5819

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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2448 KiB

Open AccessArticle

Mechanistic and Structural Insight to an Evolved Benzoylformate Decarboxylase with Enhanced Pyruvate Decarboxylase Activity

by Forest H. Andrews, Cindy Wechsler, Megan P. Rogers, Danilo Meyer, Kai Tittmann and Michael J. McLeish

Catalysts 2016, 6(12), 190; https://doi.org/10.3390/catal6120190 - 30 Nov 2016

Cited by 3 | Viewed by 5113

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 K_m value for pyruvate and, concomitantly, a decrease in the k_cat 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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2077 KiB

Open AccessArticle

Efficient Production of Enantiopure d-Lysine from l-Lysine by a Two-Enzyme Cascade System

by Xin Wang, Li Yang, Weijia Cao, Hanxiao Ying, Kequan Chen and Pingkai Ouyang

Catalysts 2016, 6(11), 168; https://doi.org/10.3390/catal6110168 - 30 Oct 2016

Cited by 9 | Viewed by 6962

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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3441 KiB

Open AccessFeature PaperArticle

Covalent Immobilization of Candida rugosa Lipase at Alkaline pH and Their Application in the Regioselective Deprotection of Per-O-acetylated Thymidine

by Cintia W. Rivero and Jose M. Palomo

Catalysts 2016, 6(8), 115; https://doi.org/10.3390/catal6080115 - 02 Aug 2016

Cited by 23 | Viewed by 6302

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

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5815 KiB

Open AccessReview

Old Yellow Enzyme-Catalysed Asymmetric Hydrogenation: Linking Family Roots with Improved Catalysis

by Anika Scholtissek, Dirk Tischler, Adrie H. Westphal, Willem J. H. Van Berkel and Caroline E. Paul

Catalysts 2017, 7(5), 130; https://doi.org/10.3390/catal7050130 - 29 Apr 2017

Cited by 82 | Viewed by 12295

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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6342 KiB

Open AccessFeature PaperReview

Tandem Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis

by Yajie Wang and Huimin Zhao

Catalysts 2016, 6(12), 194; https://doi.org/10.3390/catal6120194 - 05 Dec 2016

Cited by 53 | Viewed by 11281

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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