- Characterization of xenobiotic reductase A (XenA): Study of active site residues, substrate spectrum and stability
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Xenobiotic reductase A (XenA) has broad catalytic activity and reduces various α,β-unsaturated and nitro compounds with moderate to excellent stereoselectivity. Single mutants C25G and C25V are able to reduce nitrobenzene, a non-active substrate for the wild type, to produce aniline. Total turnover is dominated by chemical rather than thermal instability. The Royal Society of Chemistry 2010.
- Yanto, Yanto,Yu, Hua-Hsiang,Hall, Melanie,Bommarius, Andreas S.
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Read Online
- A robust and stereocomplementary panel of ene-reductase variants for gram-scale asymmetric hydrogenation
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We report an engineered panel of ene-reductases (ERs) from Thermus scotoductus SA-01 (TsER) that combines control over facial selectivity in the reduction of electron deficient C[dbnd]C double bonds with thermostability (up to 70 °C), organic solvent tolerance (up to 40 % v/v) and a broad substrate scope (23 compounds, three new to literature). Substrate acceptance and facial selectivity of 3-methylcyclohexenone was rationalized by crystallisation of TsER C25D/I67T and in silico docking. The TsER variant panel shows excellent enantiomeric excess (ee) and yields during bi-phasic preparative scale synthesis, with isolated yield of up to 93 % for 2R,5S-dihydrocarvone (3.6 g). Turnover frequencies (TOF) of approximately 40 000 h?1 were achieved, which are comparable to rates in hetero- and homogeneous metal catalysed hydrogenations. Preliminary batch reactions also demonstrated the reusability of the reaction system by consecutively removing the organic phase (n-pentane) for product removal and replacing with fresh substrate. Four consecutive batches yielded ca. 27 g L?1 R-levodione from a 45 mL aqueous reaction, containing less than 17 mg (10 μM) enzyme and the reaction only stopping because of acidification. The TsER variant panel provides a robust, highly active and stereocomplementary base for further exploitation as a tool in preparative organic synthesis.
- Nett, Nathalie,Duewel, Sabine,Schmermund, Luca,Benary, Gerrit E.,Ranaghan, Kara,Mulholland, Adrian,Opperman, Diederik J.,Hoebenreich, Sabrina
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- Metals in Biotechnology: Cr-Driven Stereoselective Reduction of Conjugated C=C Double Bonds
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Elemental metals are shown to be suitable sacrificial electron donors to drive the stereoselective reduction of conjugated C=C double bonds using Old Yellow Enzymes as catalysts. Both direct electron transfer from the metal to the enzyme as well as mediated electron transfer is feasible, although the latter excels by higher reaction rates. The general applicability of this new chemoenzymatic reduction method is demonstrated, and current limitations are outlined.
- Rauch, Marine C. R.,Gallou, Yann,Delorme, Léna,Paul, Caroline E.,Arends, Isabel W. C. E.,Hollmann, Frank
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p. 1112 - 1115
(2019/12/27)
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- Solar-Assisted eBiorefinery: Photoelectrochemical Pairing of Oxyfunctionalization and Hydrogenation Reactions
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Inspired by natural photosynthesis, biocatalytic photoelectrochemical (PEC) platforms are gaining prominence for the conversion of solar energy into useful chemicals by combining redox biocatalysis and photoelectrocatalysis. Herein, we report a dual biocatalytic PEC platform consisting of a molybdenum (Mo)-doped BiVO4 (Mo:BiVO4) photoanode and an inverse opal ITO (IO-ITO) cathode that gives rise to the coupling of peroxygenase and ene-reductase-mediated catalysis, respectively. In the PEC cell, the photoexcited electrons generated from the Mo:BiVO4 are transferred to the IO-ITO and regenerate reduced flavin mononucleotides to drive ene-reductase-catalyzed trans-hydrogenation of ketoisophrone to (R)-levodione. Meanwhile, the photoactivated Mo:BiVO4 evolves H2O2 in situ via a two-electron water-oxidation process with the aid of an applied bias, which simultaneously supplies peroxygenases to drive selective hydroxylation of ethylbenzene into enantiopure (R)-1-phenyl-1-hydroxyethane. Thus, the deliberate integration of PEC systems with redox biocatalytic reactions can simultaneously produce valuable chemicals on both electrodes using solar-powered electrons and water.
- Choi, Da Som,Hollmann, Frank,Kim, Jinhyun,Park, Chan Beum
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supporting information
p. 15886 - 15890
(2020/07/06)
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- Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
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In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
- Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
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supporting information
p. 80 - 84
(2019/01/04)
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- Enantio- A nd regioselective: Ene-reductions using F420H2-dependent enzymes
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In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- A nd chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated ketones and aldehydes with good conversions (>99%) and excellent regioselectivities and enantiomeric excesses (>99% ee). Noteworthily, FDRs typically display an opposite enantioselectivity when compared to the well established FMN-dependent Old Yellow Enzymes (OYEs).
- Mathew, Sam,Trajkovic, Milos,Kumar, Hemant,Nguyen, Quoc-Thai,Fraaije, Marco W.
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supporting information
p. 11208 - 11211
(2018/10/15)
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- Pinpointing a Mechanistic Switch Between Ketoreduction and “Ene” Reduction in Short-Chain Dehydrogenases/Reductases
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Three enzymes of the Mentha essential oil biosynthetic pathway are highly homologous, namely the ketoreductases (?)-menthone:(?)-menthol reductase and (?)-menthone:(+)-neomenthol reductase, and the “ene” reductase isopiperitenone reductase. We identified a rare catalytic residue substitution in the last two, and performed comparative crystal structure analyses and residue-swapping mutagenesis to investigate whether this determines the reaction outcome. The result was a complete loss of native activity and a switch between ene reduction and ketoreduction. This suggests the importance of a catalytic glutamate vs. tyrosine residue in determining the outcome of the reduction of α,β-unsaturated alkenes, due to the substrate occupying different binding conformations, and possibly also to the relative acidities of the two residues. This simple switch in mechanism by a single amino acid substitution could potentially generate a large number of de novo ene reductases.
- Lygidakis, Antonios,Karuppiah, Vijaykumar,Hoeven, Robin,Ní Cheallaigh, Aisling,Leys, David,Gardiner, John M.,Toogood, Helen S.,Scrutton, Nigel S.
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supporting information
p. 9596 - 9600
(2016/08/10)
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- Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes
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The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread expl
- Knaus, Tanja,Paul, Caroline E.,Levy, Colin W.,De Vries, Simon,Mutti, Francesco G.,Hollmann, Frank,Scrutton, Nigel S.
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supporting information
p. 1033 - 1039
(2016/02/05)
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- Recombinant Cyanobacteria for the Asymmetric Reduction of C=C Bonds Fueled by the Biocatalytic Oxidation of Water
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A recombinant enoate reductase was expressed in cyanobacteria and used for the light-catalyzed, enantioselective reduction of C=C bonds. The coupling of oxidoreductases to natural photosynthesis allows asymmetric syntheses fueled by the oxidation of water. Bypassing the addition of sacrificial cosubstrates as electron donors significantly improves the atom efficiency and avoids the formation of undesired side products. Crucial factors for product formation are the availability of NADPH and the amount of active enzyme in the cells. The efficiency of the reaction is comparable to typical whole-cell biotransformations in E. coli. Under optimized conditions, a solution of 100 mg prochiral 2-methylmaleimide was reduced to optically pure 2-methylsuccinimide (99 % ee, 80 % yield of isolated product). High product yields and excellent optical purities demonstrate the synthetic usefulness of light-catalyzed whole-cell biotransformations using recombinant cyanobacteria.
- K?ninger, Katharina,Gómez Baraibar, álvaro,Mügge, Carolin,Paul, Caroline E.,Hollmann, Frank,Nowaczyk, Marc M.,Kourist, Robert
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supporting information
p. 5582 - 5585
(2016/05/09)
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- Cell-free protein engineering of Old Yellow Enzyme 1 from Saccharomyces pastorianus
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In protein engineering, cell-free transcription/translation of linear mutagenic DNA templates can tremendously accelerate and simplify the screening of enzyme variants. Using the RApid Parallel Protein EvaluatoR (RAPPER) protocol, we have evaluated the impact of amino acid substitutions and loop truncations on substrate specificity and stereoselectivity of Old Yellow Enzyme 1 from Saccharomyces pastorianus. Our study demonstrates the benefit of systematically assessing amino acid variations including substrate profiling to explore sequence-function space.
- Quertinmont, Leann T.,Lutz, Stefan
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p. 7282 - 7287
(2016/10/29)
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- Complete Enzymatic Oxidation of Methanol to Carbon Dioxide: Towards More Eco-Efficient Regeneration Systems for Reduced Nicotinamide Cofactors
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A novel system for in situ regeneration of reduced nicotinamide cofactors (NADH) is proposed: through a cascade of alcohol dehydrogenase (ADH), formaldehyde dismutase (FDM) and formate dehydrogenase (FDH) complete oxidation of methanol to carbon dioxide (CO2) is coupled to the regeneration of NADH. As a consequence, from one equivalent of methanol three equivalents of NADH can be obtained. The feasibility of this cascade is demonstrated at the examples of an NADH-dependent reduction of conjugated C=C-double bonds (catalysed by an enoate reductase) and the NADH-dependent hydroxylation of phenols (catalysed by a monooxygenase). The major limitation of the current regeneration system is the comparably poor catalytic efficiency of the methanol oxidation step (low kcat and high KM value of the ADH used) necessitating higher than theoretical methanol concentrations.
- Kara, Selin,Schrittwieser, Joerg H.,Gargiulo, Serena,Ni, Yan,Yanase, Hideshi,Opperman, Diederik J.,Van Berkel, Willem J. H.,Hollmann, Frank
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supporting information
p. 1687 - 1691
(2015/06/02)
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- NAD(P)h-independent asymmetric C=C bond reduction catalyzed by ene reductases by using artificial co-substrates as the hydrogen donor
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To develop a nicotinamide-independent single flavoenzyme system for the asymmetric bioreduction of C=C bonds, four types of hydrogen donor, encompassing more than 50 candidates, were investigated. Six highly potent, cheap, and commercially available co-substrates were identified that (under the optimized conditions) resulted in conversions and enantioselectivities comparable with, or even superior to, those obtained with traditional two-enzyme nicotinamide adenine dinucleotide phosphate (NAD(P)H)-recycling systems.
- Winkler, Christoph K.,Clay, Dorina,Entner, Marcello,Plank, Markus,Faber, Kurt
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p. 1403 - 1409
(2014/04/03)
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- Enzymatic hydrogenation of diverse activated alkenes. Identification of two Bacillus old yellow enzymes with broad substrate profiles
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By whole cell transformation, 32 out of 71 strains showed OYEs activity toward maleimide in the first round screening. Among them, a Bacillus strain was identified to be active toward a selection of substrates with different electron-withdrawing groups. Two OYE homologous genes, bac-oye1 and bac-oye2 were cloned from this strain and overexpressed in Escherichia coli BL21(DE3). The recombinant enzyme Bac-OYE2 showed a broader pH range (6.0-10.5), while Bac-OYE1 was so sensitive to pH that it lost most of the enzyme activity below pH 6.0 or above pH 9.0. The reaction temperature exerted similar effects on the activities of both enzymes, but the stability of Bac-OYE2 was more sensitive to the temperature than Bac-OYE1. In addition to α,β-unsaturated aldehydes, ketones, nitroalkenes, and the double activated carboxylic acids, esters, nitriles and cyclic imides, Bac-OYE1 and Bac-OYE2 also exhibited activities toward the "borderline" substrates such as unsaturated lactones, mono carboxylic esters, showing their broader substrate scopes. These enzymes also had excellent enantioselectivity as evidenced by the reductions of several α,β-unsaturated cyclic ketones, α-substituted α,β-unsaturated carboxylic esters and 2-methyl maleimide. For example, methyl 2-acetamidoacrylate was reduced by Bac-OYE1 with >99% conversion and >99% ee.
- Zhang, Hailing,Gao, Xiuzhen,Ren, Jie,Feng, Jinhui,Zhang, Tongcun,Wu, Qiaqing,Zhu, Dunming
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p. 118 - 125
(2014/05/20)
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- Mimicking nature: Synthetic nicotinamide cofactors for C=C bioreduction using enoate reductases
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A series of synthetic nicotinamide cofactors were synthesized to replace natural nicotinamide cofactors and promote enoate reductase (ER) catalyzed reactions without compromising the activity or stereoselectivity of the bioreduction process. Conversions and enantioselectivities of >99% were obtained for C=C bioreductions, and the process was successfully upscaled. Furthermore, high chemoselectivity was observed when employing these nicotinamide cofactor mimics (mNADs) with crude extracts in ER-catalyzed reactions.
- Paul, Caroline E.,Gargiulo, Serena,Opperman, Diederik J.,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,Taglieber, Andreas,Arends, Isabel W. C. E.,Hollmann, Frank
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supporting information
p. 180 - 183
(2013/04/24)
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- More efficient redox biocatalysis by utilising 1,4-butanediol as a 'smart cosubstrate'
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1,4-Butanediol is shown to be an efficient cosubstrate to promote NAD(P)H-dependent redox biocatalysis. The thermodynamically and kinetically inert lactone coproduct makes the regeneration reaction irreversible. Thereby not only the molar surplus of cosubstrate is dramatically reduced but also faster reaction rates are obtained.
- Kara, Selin,Spickermann, Dominik,Schrittwieser, Joerg H.,Leggewie, Christian,Van Berkel, Willem J. H.,Arends, Isabel W. C. E.,Hollmann, Frank
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p. 330 - 335
(2013/03/29)
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- Nicotinamide-dependent Ene reductases as alternative biocatalysts for the reduction of activated alkenes
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Four NAD(P)H-dependent non-flavin ene reductases have been investigated for their ability to reduce activated C=C bonds in an asymmetric fashion by using 20 structurally diverse substrates. In comparison with flavin-dependent Old Yellow Enzyme homologues, a higher degree of electronic activation was required, because the best activities were obtained with enals and nitroalkenes rather than enones and carboxylic esters. Although FaEO from Fragaria x ananassa (strawberry) and its homologue SlEO from Solanum lycopersicum (tomato) exhibited a narrow substrate spectrum, progesterone 5β-reductase (At5β-StR) from Arabidopsis thaliana (thale cress) and leukotriene B4 12-hydroxydehydrogenase (LTB4DH/PGR) from Rattus norvegicus (rat) appear to be promising candidates, in particular for the asymmetric bioreduction of open-chain enals, nitroalkenes and α,β-unsaturated γ-butyrolactones. Competing nitro reduction and non-enzymatic Weitz-Scheffer epoxidation were largely suppressed. Electronically activated alkenes have been stereoselectively reduced by using a single-enzyme-cofactor system employing nicotinamide-dependent non-flavin ene reductases. Copyright
- Durchschein, Katharina,Wallner, Silvia,MacHeroux, Peter,Schwab, Wilfried,Winkler, Thorsten,Kreis, Wolfgang,Faber, Kurt
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p. 4963 - 4968
(2013/01/14)
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- A novel ene-reductase from Synechococcus sp. PCC 7942 for the asymmetric reduction of alkenes
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The increasing demand for enantiopure molecules in the pharmaceutical and fine-chemical industry requires the availability of well-characterized and efficient biocatalysts for asymmetric syntheses. Thereby, asymmetric reduction of alkenes represents one of the most employed reactions for the production of chiral molecules. Here, we present a novel ene-reductase from the cyanobacterium Synechococcus sp. PCC 7942, a member of the old yellow enzyme family, capable of reducing CC bonds in a anti-specific fashion. We evaluated its biocatalytic potential by characterizing the substrate spectrum, cofactor preference, stereoselectivity and biochemical properties. This NADPH-dependent flavoprotein accepted a wide range of activated alkenes and displayed a pH optimum between pH 7.6 and pH 8.6. A C-terminal His6-tag decreased the enzyme activity 2.7-fold, but did not influence the stereoselectivity. The reduction of (R)-carvone and 2-methylmaleimide yielded (R)-products with high optical purities (98% de and >99% ee, respectively), pointing out the applicability of this new biocatalyst in the stereoselective production of chiral compounds.
- Fu, Yilei,Hoelsch, Kathrin,Weuster-Botz, Dirk
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p. 1988 - 1997
(2013/02/25)
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- The substrate spectra of pentaerythritol tetranitrate reductase, morphinone reductase, N-ethylmaleimide reductase and estrogen-binding protein in the asymmetric bioreduction of activated alkenes
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Four flavoproteins from the old yellow enzyme (OYE) family, pentaerythritol tetranitrate (PETNR) reductase, N-ethylmaleimide reductase (NEMR), morphinone reductase (MorR) and estrogen-binding protein (EBP1), exhibited a broad substrate tolerance by accepting conjugated enals, enones, imides, dicarboxylic acids and esters, as well as a nitroalkene and therefore can be employed for the asymmetric bioreduction of carbon-carbon double (C=C) bonds. In particular, morphinone reductase and estrogen-binding protein often showed a complementary stereochemical preference in comparison to that of previously investigated OYES.
- Mueller, Nicole J.,Stueckler, Clemens,Hauer, Bernhard,Baudendistel, Nina,Housden, Hazel,Bruce, Neil C.,Faber, Kurt
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experimental part
p. 387 - 394
(2010/06/11)
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- Nitroreductase from Salmonella typhimurium: Characterization and catalytic activity
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The biocatalytic activity of nitroreductase from Salmonella typhimurium (NRSal) was investigated for the reduction of α,β-unsaturated carbonyl compounds, nitroalkenes, and nitroaromatics. The synthesized gene was subcloned into a pET28 overexpression system in E.coli BL21 strain, and the corresponding expressed protein was purified to homogeneity with 15% protein mass yield and 41% of total activity recovery. NRSal showed broad substrate acceptance for various nitro compounds such as 1-nitrocyclohexene and aliphatic nitroalkenes (alkene reductase activity), as well as nitrobenzene (nitroreductase activity), with substrate conversion efficiency of > 95%. However, the reduction of enones was generally low, proceeding albeit with high stereoselectivity. The efficient biocatalytic reduction of substituted nitroalkenes provides a route for the preparation of the corresponding nitroalkanes. NRSal also demonstrated the first single isolated enzyme-catalyzed reduction of nitrobenzene to aniline through the formation of nitrosobenzene and phenylhydroxylamine as intermediates. However, chemical condensation of the two intermediates to produce azoxybenzene currently limits the yield of aniline.
- Yanto, Yanto,Hall, Melanie,Bommarius, Andreas S.
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scheme or table
p. 1826 - 1832
(2010/08/06)
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- Biocatalysis with thermostable enzymes: Structure and properties of a thermophilic 'ene'-reductase related to old yellow enzyme
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We report the crystal structure of a thermophilic "ene" reductase (TOYE) isolated from Thermoanaerobacter pseudethanolicus E39. The crystal structure reveals a tetrameric enzyme and an active site that is relatively large compared to most other structurally determined and related Old Yellow Enzymes. The enzyme adopts higher order oligomeric states (octamers and dodecamers) in solution, as revealed by sedimentation velocity and multiangle laser light scattering. Bead modelling indicates that the solution structure is consistent with the basic tetrameric structure observed in crystallographic studies and electron microscopy. TOYE is stable at high temperatures (T m > 70°C) and shows increased resistance to denaturation in water-miscible organic solvents compared to the mesophilic Old Yellow Enzyme family member, pentaerythritol tetranitrate reductase. TOYE has typical ene-reductase properties of the Old Yellow Enzyme family. There is currently major interest in using Old Yellow Enzyme family members in the preparative biocatalysis of a number of activated alkenes. The increased stability of TOYE in organic solvents is advantageous for biotransformations in which water-miscible organic solvents and biphasic reaction conditions are required to both deliver novel substrates and minimize product racemisation.
- Adalbjoernsson, Bjoern V.,Toogood, Helen S.,Fryszkowska, Anna,Pudney, Christopher R.,Jowitt, Thomas A.,Leys, David,Scrutton, Nigel S.
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experimental part
p. 197 - 207
(2010/12/19)
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- Asymmetrie reduction of activated alkenes by pentaerythritol tetranitrate reductase: Specificity and control of stereochemical outcome by reaction optimisation
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We show that pentaerythritol tetranitrate reductase (PETNR), a member of the 'ene' reductase old yellow enzyme family, catalyses the asymmetric reduction of a variety of industrially relevant activated α,β-unsaturated alkenes including enones, enals, maleimides and nitroalkenes. We have rationalised the broad substrate specificity and stereochemical outcome of these reductions by reference to molecular models of enzyme-substrate complexes based on the crystal complex of the PETNR with 2cyclohexenone 4a. The optical purity of products is variable (49-99% ee), depending on the substrate type and nature of substituents. Generally, high enantioselectivity was observed for reaction products with stereogenic centres at Cβ (>99% ee). However, for the substrates existing in two isomeric forms (e.g., citral 11a or nitroalkenes 18-19a), an enantio-divergent course of the reduction of E/Z-forms may lead to lower enantiopurities of the products. We also demonstrate that the poor optical purity obtained for products with stereogenic centres at Ca is due to non-enzymatic racemisation. In reactions with ketoisophorone 3a we show that product racemisation is prevented through reaction optimisation, specifically by shortening reaction time and through control of solution pH. We suggest this as a general strategy for improved recovery of optically pure products with other biocatalytic conversions where there is potential for product racemisation.
- Fryszkowska, Anna,Toogood, Helen,Sakuma, Michiyo,Gardiner, John M.,Stephens, Gill M.,Scrutton, Nigel S.
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supporting information; experimental part
p. 2976 - 2990
(2010/03/25)
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- Photoenzymatic reduction of C=C double bonds
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A simplified procedure for cell-free biocatalytic reductions of conjugated C=C double bonds using old yellow enzymes (OYEs) is reported. Instead of indirectly regenerating YqjM (an OYE homologue from B. subtilis) or NemA (N-ethylmaleimide reductase from E
- Grau, Maria Mifsud,Van Der Toorn, John C.,Otten, Linda G.,Macheroux, Peter,Taglieber, Andreas,Zilly, Felipe E.,Arends, Isabel W. C. E.,Hollmann, Frank
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experimental part
p. 3279 - 3286
(2010/07/07)
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- Asymmetric bioreduction of C=C bonds using enoate reductases OPR1, OPR3 and YqjM: Enzyme-based stereocontrol
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Three cloned enoate reductases from the "old yellow enzyme" family of flavoproteins were investigated in the asymmetric bioreduction of activated alkenes. 12-Oxophytodienoate reductase isoenzymes OPR1 and OPR3 from Lycopersicon esculentum (tomato), and YqjM from Bacillus subtilis displayed a remarkably broad substrate spectrum by reducing α,β-unsaturated aldehydes, ketones, maleimides and nitroalkenes. The reaction proceeded with absolute chemoselectivity-only the conjugated C=C bond was reduced, while isolated olefins and carbonyl groups remained intact-with excellent stereoselectivities (ees up to >99%). Upon reduction of a nitroalkene, the stereochemical outcome could be determined via choice of the appropriate enzyme (OPR1 versus OPR3 or YqjM), which furnished the corresponding enantiomeric nitroalkanes in excellent ee. Molecular modelling suggests that this "enzyme-based stereocontrol" is caused by subtle differences within the active site geometries.
- Hall, Melanie,Stueckler, Clemens,Ehammer, Heidemarie,Pointner, Eva,Oberdorfer, Gustav,Gruber, Karl,Hauer, Bernard,Stuermer, Rainer,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
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experimental part
p. 411 - 418
(2009/04/10)
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- Asymmetric bioreduction of activated C=C bonds using Zymomonas mobilis NCR enoate reductase and old yellow enzymes OYE 1-3 from yeasts
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The asymmetric bioreduction of C=C-bonds bearing an electron-withdrawing group, such as an aldehyde, ketone, imide, nitro, carboxylic acid, or ester moiety by a novel enoate reductase from Zymomonas mobilis and Old Yellow Enzymes OYE 1-3 from yeasts furnished the corresponding saturated products in up to >99%ee. Depending on the substrate type, stereocontrol was achieved by variation of the substrate structure, by switching the (E/Z) geometry of the alkene or by choice of the appropriate enzyme. This substrate- or enzyme-based stereocontrol allowed access to the opposite enantiomeric products. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Hall, Melanie,Stueckler, Clemens,Hauer, Bernhard,Stuermer, Rainer,Friedrich, Thomas,Breuer, Michael,Kroutil, Wolfgang,Faber, Kurt
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scheme or table
p. 1511 - 1516
(2009/04/11)
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- Microbial Conversion of 4-Oxoisophorone by Thermophile, Thermomonospora curvata
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Thermomonospora curvata IFO 12384 was selected from many thermophiles tested as a strain capable of converting 2,6,6-trimethyl-2-cyclohexene-1,4-dione (4-oxoisophorone) into (6R)-2,2,6-trimethyl-1,4-cyclohexadione ((3R)-dihydro-4-oxoisophorone) efficiently.The other conversion products were also isolated and identified by spectrometry.Based on the results of experiments with a degradation sequence, a conversion pathway for 4-oxoisophorone by this thermophile is proposed.The effects of nutritional conditions, temperature, initial pH and the concentration of the substrate on the conversion were examined.Under the optimal conditions, the conversion ratio of 4-oxoisophorone to (3R)-dihydro-4-oxoisophorone was over 95percent.The production rate of (3R)-dihydro-4-oxoisophorone was 86 mg per 1 g of dry cells per hr.
- Hori, Nobuaki,Hieda, Tadaharu,Mikami, Yoichi
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p. 123 - 130
(2007/10/02)
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