Enantioconvergent Biohydrolysis of Racemic Styrene Oxide to R-phenyl-1, 2-ethanediol by a Newly Isolated Filamentous Fungus Aspergillus tubingensis TF1

Duarah, Aparajita; Goswami, Anindya; Bora, Tarun C.; Talukdar, Madhumita Choudhury; Gogoi, Barnali

doi:10.1007/s12010-013-0324-x

Cited by 10 publications

(4 citation statements)

References 21 publications

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“…These findings demonstrated that the MIP@g-C 3 N 4 nanocomposites were capable of catalytically activating the H 2 O 2 to form ˙OH radicals in a peroxidase-like catalytic reaction, which subsequently play critical roles in oxidizing TMB to produce a TMB oxide with a blue color. 57 The peroxidase-like catalytic mechanism of MIP@g-C 3 N 4 nanocomposites was proposed and is illustrated in Scheme 2. During the catalytic oxidation reaction, the MIP@g-C 3 N 4 nanocomposites have the potential to operate as peroxidase mimics, which will help facilitate the transfer of electrons between TMB and H 2 O 2 .…”

Section: Resultsmentioning

confidence: 99%

Selective and sensitive on-site colorimetric detection of 4,4′-isopropylidenediphenol using non-enzymatic molecularly imprinted graphitic carbon nitride hybrids in milk and water samples

Komal

Arulmozhi

et al. 2023

New J. Chem.

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Section: Resultsmentioning

confidence: 99%

Selective and sensitive on-site colorimetric detection of 4,4′-isopropylidenediphenol using non-enzymatic molecularly imprinted graphitic carbon nitride hybrids in milk and water samples

Komal

Arulmozhi

et al. 2023

New J. Chem.

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“…An interesting enantioconvergent process with whole cells of Aspergillus tubingensis TF1 was recently described by Duarah et al [87]. (R)-Phenyl-1,2-ethanediol was isolated from the reaction mixture in 97% ee after 45 min, reaching >99% conversion of racemic SO (8.75 mM).…”

Section: Styrene Oxidementioning

confidence: 99%

“…Using SO as a substrate mimic, SgcF and NcsF2 were shown to be enantiocomplementary, leading to the formation of (R)phenyl-1,2-ethanediol in 99% ee and 87% yield from racemic SO (14 mM) when used together in the reaction mixture (Lin et al, 2010). An interesting enantioconvergent process with whole cells of Aspergillus tubingensis TF1 was very recently described by Duarah et al (Duarah et al, 2013). (R)-phenyl-1,2-ethanediol was isolated from the reaction mixture in 97% ee after 45 min, reaching >99% conversion of racemic SO (8.75 mM).…”

Section: Styrene Oxidementioning

confidence: 99%

Epoxide Hydrolases and their Application in Organic Synthesis

2016

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c h a p t e r 8 INTRODUCTIONOrganic chemists have become interested in enzymes as catalysts due to their high efficiencies and specificities. Moreover, recent progress in molecular biology and enzyme-related research areas enabled and simplified the production and purifica tion of recombinant enzymes in large quantities and their engineering toward tailormade biocatalysts using straightforward mutagenesis and screening techniques. This is also true for epoxide hydrolases (EHs), as evidenced by the many published research papers about the synthetic applications of naturally occurring or engi neered EHs. EHs catalyze the opening of oxirane rings, generating a vicinal diol as the final product ( Figure 8.1). From a synthetic chemistry point of view, the most valuable EHs are those with either (i) high enantioselectivities or (ii) a combination of low enantio preference with a high level of enantioconvergence. While the former generate enan tiopure epoxides with a maximum yield of 50% in a kinetic resolution process, the latter produce ideally an enantiopure diol product with a theoretical yield of 100%. Thus, EHs provide convenient access to enantiopure epoxides or diols from racemic epoxides. Furthermore, the enantiopure diols can then often be chemically trans formed back to the corresponding epoxides with no effect on the enantiomeric excess (ee). High values of enantioselectivity or enantioconvergence are a consequence of particular enzyme-substrate interactions, which can be modulated by specific reac tion conditions or through the exchange of specific amino acids of the biocatalyst. The final stereochemical outcome of an EH-catalyzed reaction depends solely on the regioselectivity coefficients, which determine the absolute configuration and the ee of the diol product when the reaction reaches 100% conversion. During the reaction, the oxirane ring of each enantiomer is often attacked at either carbon atom, resulting in a mixture of diol enantiomers (Figure 8.2). Unfortunately, several authors used the product-derived E-value, E P (calculated from c and ee P using Sih's equation; see Ref.[1]) for characterizing the stereochemistry of the diol formation of an EH-mediated hydrolysis reaction [2,3]. This is wrong and misleading for epoxide-opening reac tions since there are two possible positions of attack for each oxirane enantiomer. The ideal enantioconvergent EH leads to deracemization of a racemic mixture of an epox ide and exhibits reversed regioselectivity for either substrate enantiomer, that is,

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“…The kinetic resolution of rac-epoxides by highly enantioselective EHs provides an environment-friendly bioprocess for the preparation of (R)-or (S)-epoxides with an intrinsic limitation of 50% yield 11 . However, the majority of wild-type (WT) EHs displayed unsatisfactory catalytic activity and/or E value, making them unable to be effectively used in the kinetic resolution of rac-epoxides 12 .…”

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confidence: 99%

Significant improvement in catalytic activity and enantioselectivity of a Phaseolus vulgaris epoxide hydrolase, PvEH3, towards ortho-cresyl glycidyl ether based on the semi-rational design

Zhang

Liu

et al. 2020

Sci Rep

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The investigation of substrate spectrum towards five racemic (rac-) aryl glycidyl ethers (1a-5a) indicated that E. coli/pveh3, an E. coli BL21(DE3) transformant harboring a PvEH3-encoding gene pveh3, showed the highest EH activity and enantiomeric ratio (E) towards rac-3a. For efficiently catalyzing the kinetic resolution of rac-3a, the activity and E value of PvEH3 were further improved by site-directed mutagenesis of selected residues. Based on the semi-rational design of an NC-loop in PvEH3, four single-site variants of pveh3 were amplified by PCR, and intracellularly expressed in E. coli BL21(DE3), respectively. E. coli/pveh3 E134K and /pveh3 T137P had the enhanced EH activities of 15.3 ± 0.4 and 16.1 ± 0.5 U/g wet cell as well as E values of 21.7 ± 1.0 and 21.2 ± 1.1 towards rac-3a. Subsequently, E. coli/pveh3 E134K/T137P harboring a double-site variant gene was also constructed, having the highest EH activity of 22.4 ± 0.6 U/g wet cell and E value of 24.1 ± 1.2. The specific activity of the purified PvEH3 E134K/T137P (14.5 ± 0.5 U/mg protein) towards rac-3a and its catalytic efficiency (k cat /K m of 5.67 mM −1 s −1 ) for (S)-3a were 1.7-and 3.54-fold those (8.4 ± 0.3 U/mg and 1.60 mM −1 s −1 ) of PvEH3. The gram-scale kinetic resolution of rac-3a using whole wet cells of E. coli/pveh3 E134K/T137P was performed at 20 °C for 7.0 h, producing (R)-3a with 99.4% ee s and 38.5 ± 1.2% yield. Additionally, the mechanism of PvEH3 E134K/T137P with remarkably improved E value was analyzed by molecular docking simulation.Enantiomeric isomers of chiral compounds, such as (R)-and (S)-enantiomers of a racemic drug, usually possess different and even antagonistic biological activities and pharmacological functions 1 . Since the early 1990s, there has been an ever-increasing demand for the optically pure epoxides and their corresponding vicinal diols, which are versatile and highly value-added building blocks applied diffusely in the pharmaceutical, fine chemical and agrochemical industries 2,3 . For examples, (S)-styrene oxide (SO) is a crucial drug intermediate for the synthesis of nematocide, anticancer agent -Levamisole, and anti-HIV agent -(−)-Hyperolactone C 4 , while (R)-and (S)-aryl/alkyl glycidyl ethers, such as (S)-benzyl glycidyl ether (1a) and (R)-ortho-cresyl glycidyl ether (3a), for the synthesis of chiral amino alcohols and β-blockers 5 .Along with a green wave of global industrialization, the biocatalysis by whole cells or enzymes, having high enantio-and/or regio-selectivity and little or no byproducts, is recognized as an alternative or supplement to the chemocatalysis that requires hazardous metals and expensive chiral ligands, exampled by Jacobsen's asymmetric ring-opening hydrolysis and epoxidation 6,7 . Epoxide hydrolases (EHs, EC 3.3.2.-), existing widely in organisms These changes in kinetic parameters suggested that the combinatorial substitution, E134K and T137P, in the NC-loop of PvEH3 had a significantly positive effect on its enantiopreference for (S)-3a.

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Enantioconvergent Biohydrolysis of Racemic Styrene Oxide to R-phenyl-1, 2-ethanediol by a Newly Isolated Filamentous Fungus Aspergillus tubingensis TF1

Cited by 10 publications

References 21 publications

Selective and sensitive on-site colorimetric detection of 4,4′-isopropylidenediphenol using non-enzymatic molecularly imprinted graphitic carbon nitride hybrids in milk and water samples

Selective and sensitive on-site colorimetric detection of 4,4′-isopropylidenediphenol using non-enzymatic molecularly imprinted graphitic carbon nitride hybrids in milk and water samples

Epoxide Hydrolases and their Application in Organic Synthesis

Significant improvement in catalytic activity and enantioselectivity of a Phaseolus vulgaris epoxide hydrolase, PvEH3, towards ortho-cresyl glycidyl ether based on the semi-rational design

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