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1.
Major characteristics, substrate specificities and enantioselectivities of epoxide hydrolases from various sources are described. Epoxide hydrolase activity in yeasts is discussed in more detail and is compared with activities in other microorganisms. Constitutively produced bacterial epoxide hydrolases are highly enantioselective in the hydrolysis of 2,2- and 2,3-disubstituted epoxides. A novel bacterial limonene-1,2-epoxide hydrolase, induced by growth on monoterpenes, showed high activities and selectivities in the hydrolysis of several substituted alicyclic epoxides. Constitutively produced epoxide hydrolases are found in eukaryotic microorganisms. Enzymes from filamentous fungi are useful biocatalysts in the resolution of aryl- and substituted alicyclic epoxides. Yeast epoxide hydrolase activity has been demonstrated for the enantioselective hydrolysis of various aryl-, alicyclic- and aliphatic epoxides by a strain of Rhodotorula glutinis. The yeast enzyme, moreover, is capable of asymmetric hydrolysis of meso epoxides and performs highly enantioselective resolution of unbranched aliphatic 1,2-epoxides. Screening for other yeast epoxide hydrolases shows that high enantioselectivity is restricted to a few basidiomycetes genera only. Resolution of very high substrate concentrations is possible by using selected basidiomycetes yeast strains.  相似文献   

2.
DNA shuffling and saturation mutagenesis of positions F108, L190, I219, D235, and C248 were used to generate variants of the epoxide hydrolase of Agrobacterium radiobacter AD1 (EchA) with enhanced enantioselectivity and activity for styrene oxide and enhanced activity for 1,2-epoxyhexane and epoxypropane. EchA variant I219F has more than fivefold-enhanced enantioselectivity toward racemic styrene oxide, with the enantiomeric ratio value (E value) for the production of (R)-1-phenylethane-1,2-diol increased from 17 for the wild-type enzyme to 91, as well as twofold-improved activity for the production of (R)-1-phenylethane-1,2-diol (1.96 ± 0.09 versus 1.04 ± 0.07 μmol/min/mg for wild-type EchA). Computer modeling indicated that this mutation significantly alters (R)-styrene oxide binding in the active site. Another three variants from EchA active-site engineering, F108L/C248I, I219L/C248I, and F108L/I219L/C248I, also exhibited improved enantioselectivity toward racemic styrene oxide in favor of production of the corresponding diol in the (R) configuration (twofold enhancement in their E values). Variant F108L/I219L/C248I also demonstrated 10-fold- and 2-fold-increased activity on 5 mM epoxypropane (24 ± 2 versus 2.4 ± 0.3 μmol/min/mg for the wild-type enzyme) and 5 mM 1,2-epoxyhexane (5.2 ± 0.5 versus 2.6 ± 0.0 μmol/min/mg for the wild-type enzyme). Both variants L190F (isolated from a DNA shuffling library) and L190Y (created from subsequent saturation mutagenesis) showed significantly enhanced activity for racemic styrene oxide hydrolysis, with 4.8-fold (8.6 ± 0.3 versus 1.8 ± 0.2 μmol/min/mg for the wild-type enzyme) and 2.7-fold (4.8 ± 0.8 versus 1.8 ± 0.2 μmol/min/mg for the wild-type enzyme) improvements, respectively. L190Y also hydrolyzed 1,2-epoxyhexane 2.5 times faster than the wild-type enzyme.  相似文献   

3.
Epoxide hydrolase from Aspergillus niger was immobilized onto the modified Eupergit C 250 L through a Schiff base formation. Eupergit C 250 L was treated with ethylenediamine to introduce primary amine groups which were subsequently activated with glutaraldehyde. The amount of introduced primary amine groups was 220 μmol/g of the support after ethylenediamine treatment, and 90% of these groups were activated with glutaraldehyde. Maximum immobilization of 80% was obtained with modified Eupergit C 250 L under the optimized conditions. The optimum pH was 7.0 for the free epoxide hydrolase and 6.5 for the immobilized epoxide hydrolase. The optimum temperature for both free and immobilized epoxide hydrolase was 40 °C. The free epoxide hydrolase retained 52 and 33% of its maximum activity at 40 and 60 °C, respectively after 24 h preincubation time whereas the retained activities of immobilized epoxide hydrolase at the same conditions were 90 and 75%, respectively. Immobilized epoxide hydrolase showed about 2.5-fold higher enantioselectivity than that of free epoxide hydrolase. A preparative-scale (120 g/L) kinetic resolution of racemic styrene oxide using immobilized preparation was performed in a batch reactor and (S)-styrene oxide and (R)-1-phenyl-1,2-ethanediol were both obtained with about 50% yield and 99% enantiomeric excess. The immobilized epoxide hydrolase was retained 90% of its initial activity after 5 reuses.  相似文献   

4.
Xu Y  Xu JH  Pan J  Tang YF 《Biotechnology letters》2004,26(15):1217-1221
Glycidyl aryl ethers were resolved by using lyophilized cells of Trichosporon loubierii ECU1040 having epoxide hydrolase activity. The activity and enantioselectivity depended on the structure of the aryl group. Different cell/substrate ratios also influenced the optical purity of remaining substrate. An additional stability test of the whole-cell enzyme suggests that rapid deactivation of the epoxide hydrolase was the potential reason. (R)-Epoxides were prepared in gram amounts with optical purity of 87% - 99% ee.  相似文献   

5.
6.
DNA shuffling and saturation mutagenesis of positions F108, L190, I219, D235, and C248 were used to generate variants of the epoxide hydrolase of Agrobacterium radiobacter AD1 (EchA) with enhanced enantioselectivity and activity for styrene oxide and enhanced activity for 1,2-epoxyhexane and epoxypropane. EchA variant I219F has more than fivefold-enhanced enantioselectivity toward racemic styrene oxide, with the enantiomeric ratio value (E value) for the production of (R)-1-phenylethane-1,2-diol increased from 17 for the wild-type enzyme to 91, as well as twofold-improved activity for the production of (R)-1-phenylethane-1,2-diol (1.96 +/- 0.09 versus 1.04 +/- 0.07 micromol/min/mg for wild-type EchA). Computer modeling indicated that this mutation significantly alters (R)-styrene oxide binding in the active site. Another three variants from EchA active-site engineering, F108L/C248I, I219L/C248I, and F108L/I219L/C248I, also exhibited improved enantioselectivity toward racemic styrene oxide in favor of production of the corresponding diol in the (R) configuration (twofold enhancement in their E values). Variant F108L/I219L/C248I also demonstrated 10-fold- and 2-fold-increased activity on 5 mM epoxypropane (24 +/- 2 versus 2.4 +/- 0.3 micromol/min/mg for the wild-type enzyme) and 5 mM 1,2-epoxyhexane (5.2 +/- 0.5 versus 2.6 +/- 0.0 micromol/min/mg for the wild-type enzyme). Both variants L190F (isolated from a DNA shuffling library) and L190Y (created from subsequent saturation mutagenesis) showed significantly enhanced activity for racemic styrene oxide hydrolysis, with 4.8-fold (8.6 +/- 0.3 versus 1.8 +/- 0.2 micromol/min/mg for the wild-type enzyme) and 2.7-fold (4.8 +/- 0.8 versus 1.8 +/- 0.2 micromol/min/mg for the wild-type enzyme) improvements, respectively. L190Y also hydrolyzed 1,2-epoxyhexane 2.5 times faster than the wild-type enzyme.  相似文献   

7.
We have examined the selectivity of rat liver microsomal epoxide hydrolase (EC 3.3.2.3) toward all of the possible positional isomers of benzo-ring diol epoxides and tetrahydroepoxides of benz[a]anthracene, as well as the 1,2-diol 3,4-epoxides of triphenylene. This set includes compounds with no bay region in the vicinity of the benzo-ring, a bay-region diol group, a bay-region epoxide group, and (for the triphenylene derivatives) both a bay-region diol and a bay-region epoxide. In all cases where both the tetrahydroepoxides and the corresponding diol epoxides were examined, there is a large retarding effect of hydroxyl substitution on the rate of the enzyme-catalyzed hydration. When the tetrahydroepoxides are fair or poor substrates (epoxide group in the 1,2-, 8,9-, or 10,11-position), the additional retardation introduced by adjacent hydroxyl groups causes the enzyme-catalyzed hydrolysis of the corresponding diol epoxides to be insignificantly slow or nonexistent. In contrast, a benz[a]anthracene derivative with an epoxide group in the 3,4-position, (-)-tetrahydrobenz[a]anthracene (3R,4S)-epoxide, has been identified as the best substrate known for epoxide hydrolase, with a Vmax at 37 degrees C and pH 8.4 of 6800 nmol/min/mg of protein, and the two diastereomeric (+/-)-benz[a]anthracene 1,2-diol 3,4-epoxides, unlike all the other diol epoxides examined to date, are moderately good substrates for epoxide hydrolase. This novel observation is accounted for by the fact that the very high reactivity of the tetrahydrobenz[a]anthracene 3,4-epoxide system towards epoxide hydrolase is large enough to overcome a kinetically unfavorable effect of hydroxyl substitution. The enantioselectivity and positional selectivity of the enzyme have been determined for the tetrahydro-1,2- and -3,4-epoxides of benz[a]anthracene as well as the 1,2-diol 3,4-epoxides. When the epoxide is located in the 3,4-position, the benzylic carbon is the preferred site of attack, whereas for the enantiomers of the bay-region tetrahydro-1,2-epoxides, the chemically less reactive non-benzylic carbon is preferred. The regio- and enantioselectivity of epoxide hydrolase are discussed in terms of a possible model for the hydrophobic binding site of this enzyme.  相似文献   

8.
Inverting enzyme enantioselectivity by protein engineering is still a great challenge. Lip2p lipase from Yarrowia lipolytica, which demonstrates a low S‐enantioselectivity (E‐value = 5) during the hydrolytic kinetic resolution of 2‐bromo‐phenyl acetic acid octyl esters (an important class of chemical intermediates in the pharmaceutical industry), was converted, by a rational engineering approach, into a totally R‐selective enzyme (E‐value > 200). This tremendous change in selectivity is the result of only two amino acid changes. The starting point of our strategy was the prior identification of two key positions, 97 and 232, for enantiomer discrimination. Four single substitution variants were recently identified as exhibiting a low inversion of selectivity coupled to a low‐hydrolytic activity. On the basis of these results, six double substituted variants, combining relevant mutations at both 97 and 232 positions, were constructed by site‐directed mutagenesis. This work led to the isolation of one double substituted variant (D97A‐V232F), which displays a total preference for the R‐enantiomer. The highly reversed enantioselectivity of this variant is accompanied by a 4.5‐fold enhancement of its activity toward the preferred enantiomer. The molecular docking of the R‐ and S‐enantiomers in the wild‐type enzyme and the D97A‐V232F variant suggests that V232F mutation provides a more favorable stacking interaction for the phenyl group of the R‐enantiomer, that could explain both the enhanced activity and the reversal of enantioselectivity. These results demonstrate the potential of rationally engineered mutations to further enhance enzyme activity and to modulate selectivity. Biotechnol. Bioeng. 2010;106: 852–859. © 2010 Wiley Periodicals, Inc.  相似文献   

9.
  • 1.1. The kinetic parameters of the cytosolic epoxide hydrolase were examined with two sets of spectrophotometric substrates. The (2S,3S)- and (2R,3R)-enantiomers of 4-nitrophenyl trans-2,3-epoxy-3-phenylpropyl carbonate had a Kmof 33 and 68 μm and a Vmax of 16 and 27 μmol/min/mg, respectively. With the (2S,3S)- and (2R,3R)- enantiomers of 4-nitrophenyl trans-2,3-epoxy-3-(4-nitrophenyl)propyl carbonate, cytosolic epoxide hydrolase had a KM of 8.0 and 15 μM and a Vmax of 7.8 and 5.0 μmol/min/mg, respectively.
  • 2.2. Glycidyl 4-nitrobenzoate had the lowest I50 of the compounds tested in the glycidyl 4-nitrobenzoate series (I50= 140 μM). The I50 of the (2R)-enantiomer was 3.7-fold higher. The inhibitor with the lowest i50 in the glycidol series, and the lowest I50 of any compound tested, was (2S,3S)-3-(4-nitrophenyl)glycidol (I50 = 13.0μM). It also showed the greatest difference in I50 between the enantiomers (330-fold).
  • 3.3. All enantiomers of glycidyl 4-nitrobenzoates and trans-3-phenylglycidols gave differential inhibition of cytosolic epoxide hydrolase. However, neither the (S,S)-/(S)- or (R,R)-/(R)-enantiomer always had the lower I50.
  • 4.4. Addition of one or more methyl groups to either enantiomer of glycidyl 4-nitrobenzoate resulted in increased I50. However, addition of a methyl group to C2 of either enantiomer of 3-phenylglycidol resulted in a decreased I50. Finally, when the hydroxyl group of trans-3-(4-nitrophenyl)glycidol was esterified the I50 of the (2S,3S)- but not the (2R,3R)-enantiomer increased.
  相似文献   

10.
Halohydrin dehalogenase from Agrobacterium radiobacter AD1 (HheC) shows great potential in producing valuable chiral epoxides and β-substituted alcohols. The wild-type (WT) enzyme displays a high R-enantiopreference toward most aromatic substrates, whereas no S-selective HheC has been reported to date. To obtain more enantioselective enzymes, seven noncatalytic active-site residues were subjected to iterative saturation mutagenesis (ISM). After two rounds of screening aspects of both activity and enantioselectivity (E), three outstanding mutants (Thr134Val/Leu142Met, Leu142Phe/Asn176His, and Pro84Val/Phe86Pro/Thr134Ala/Asn176Ala mutants) with divergent enantioselectivity were obtained. The two double mutants displayed approximately 2-fold improvement in R-enantioselectivity toward 2-chloro-1-phenylethanol (2-CPE) without a significant loss of enzyme activity compared with the WT enzyme. Strikingly, the Pro84Val/Phe86Pro/Thr134Ala/Asn176Ala mutant showed an inverted enantioselectivity (from an ER of 65 [WT] to an ES of 101) and approximately 100-fold-enhanced catalytic efficiency toward (S)-2-CPE. Molecular dynamic simulation and docking analysis revealed that the phenyl side chain of (S)-2-CPE bound at a different location than that of its R-counterpart; those mutations generated extra connections for the binding of the favored enantiomer, while the eliminated connections reduced binding of the nonfavored enantiomer, all of which could contribute to the observed inverted enantiopreference.  相似文献   

11.
In our effort to screen for strains producing carbonyl reductases with high activity and enantioselectivity, Saccharomyces cerevisiae CGMCC 2.396 was found to be able to catalyze the biotransformation of a series of α-haloacetophenones to Prelog's configurated alcohols in excellent optical purity (>99% ee). The optimal reaction condition was obtained after the investigation of various crucial factors. Under the optimal condition, the product was obtained with high yield (97%) and excellent enantioselectivity (>99% ee). The usefulness of this strain has been further demonstrated by the synthesis of several (R)-α-halohydrins (>99% ee) of pharmaceutical importance.  相似文献   

12.
Epoxide hydrolase from Aspergillus niger (E.C. 3.3.2.3) was immobilized by covalent linking to epoxide-activated silica gel under mild conditions. A very easy procedure allowed to prepare an immobilized biocatalyst with more than 90% retention of the initial enzymatic activity. Immobilized and free enzyme showed very similar behaviour with respect to the effect of pH on activity and stability. One benefit of immobilizing epoxide hydrolase from A. niger on silica gel was the enhanced enzyme stability in the presence of 20% DMSO. The kinetic resolution of racemic para-nitrostyrene oxide was investigated by using this new immobilized biocatalyst. The enantioselectivity of the enzyme was not altered by the immobilization reaction: both unreacted epoxide and formed diol were obtained with very high ee (99 and 92%, respectively). In addition, the biocatalyst could be easily separated from the reaction mixture and re-used for over nine cycles without any noticeable loss of enzymatic activity or change in the enantioselectivity extent. The activity of immobilized AnEH was retained for several months.  相似文献   

13.
Seeds of broad bean (Vicia faba L.) contain a hydroperoxide-dependent fatty acid epoxygenase. Hydrogen peroxide served as an effective oxygen donor in the epoxygenase reaction. Fifteen unsaturated fatty acids were incubated with V. faba epoxygenase in the presence of hydrogen peroxide and the epoxy fatty acids produced were identified. Examination of the substrate specificity of the epoxygenase using a series of monounsaturated fatty acids demonstrated that (Z)-fatty acids were rapidly epoxidized into the corresponding cis-epoxy acids, whereas (E)-fatty acids were converted into their trans-epoxides at a very slow rate. In the series of (Z)-monoenoic acids, the double bond position as well as the chain length influenced the rate of epoxidation. The best substrates were found to be palmitoleic, oleic, and myristoleic acids. Steric analysis showed that most of the epoxy acids produced from monounsaturated fatty acids as well as from linoleic and α-linolenic acids had mainly the (R),(S) configuration. Exceptions were C18 acids having the epoxide group located at C-12/13, in which cases the (S),(R) enantiomers dominated. 13(S)-Hydroxy-9(Z),11(E)-octadecadienoic acid incubated with epoxygenase afforded the epoxy alcohol 9(S),10(R)-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid as the major product. Smaller amounts of the diastereomeric epoxy alcohol 9(R),10(S)-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid as well as the α,β-epoxy alcohol 11(R),12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoic acid were also obtained. The soluble fraction of homogenate of V. faba seeds contained an epoxide hydrolase activity that catalyzed the conversion of cis-9,10-epoxyoctadecanoic acid into threo-9,10-dihydroxyoctadecanoic acid.  相似文献   

14.
《Process Biochemistry》2010,45(1):25-29
The transesterification of 1-phenyl ethanol has been carried out using lipases from Pseudomonas aeruginosa MTCC 5113, to obtain chirally pure aryl ethanols with good yield and excellent enantioselectivity. The lipase from P. aeruginosa gave good conversion and moderate enantioselectivity (ee) in organic solvents, however, when the catalytic amount of ionic liquids were added in the reaction mixture, excellent enantioselectivity was obtained. Moreover, the change in enantiomer preference was seen in the presence of catalytic amount of ionic liquids. The findings revealed that hydrophobic ionic liquids (two-phase system) were the best solvents and 4-substituted aryl ethanols were the pre-eminent substrates for such type of reactions. The preparative scale (5 g) transesterification of 1-phenylethanol using lipases from P. aeruginosa yielded S-(−)-1-phenyl ethanol with 39% yield and >99% ee in hexane and 46% yield and >99% ee in [BMIm][PF6].  相似文献   

15.
Didymosphaeria igniaria is a promising biocatalyst in asymmetric reductions of prochiral aromatic-aliphatic ketones such as acetonaphthones, acetophenones, and acetylpyridines. The organism converted the substrates mainly to (S)-alcohols. Excellent results in terms of conversion and enantioselectivity (100% yield, >99% ee) were obtained with acetonaphthones. In case of acetyl pyridines, the optical purity of the product depended on the position of the carbonyl group on the pyridine ring and followed the order 2-acetyl ? 4-acetyl > 3-acetyl-pyridine. Transformation of o-methoxy-acetophenone gave optically pure (S)-(-)-1-(2-methoxyphenyl)-ethanol in 95% yield. The transformation of para-methyl ketone gave (R)-alcohol (81% ee), whereas para-bromo ketone gave (S)-alcohol (98% ee). Monitoring of the biotransformation of these substrates over time led to the conclusion that for both substrates, non-selective carbonyl group reduction occurred in the first step, followed by selective oxidation of the (R)-isomer of p-bromo-phenylethanol and selective oxidation of the (S)-isomer of p-methyl-phenylethanol. D. igniaria exhibited poor enantioselectivity in the reduction of bicyclic aryl-aliphatic ketones such as 1- and 2-tetralones. Only (S)-5-methoxy-1-tetralol was obtained in optically pure (>99% ee) form.  相似文献   

16.
Soluble epoxide hydrolase (EH) from the potato Solanum tuberosum and an evolved EH of the bacterium Agrobacterium radiobacter AD1, EchA-I219F, were purified for the enantioconvergent hydrolysis of racemic styrene oxide into the single product (R)-1-phenyl-1,2-ethanediol, which is an important intermediate for pharmaceuticals. EchA-I219F has enhanced enantioselectivity (enantiomeric ratio of 91 based on products) for converting (R)-styrene oxide to (R)-1-phenyl-1,2-ethanediol (2.0 +/- 0.2 micromol/min/mg), and the potato EH converts (S)-styrene oxide primarily to the same enantiomer, (R)-1-phenyl-1,2-ethanediol (22 +/- 1 micromol/min/mg), with an enantiomeric ratio of 40 +/- 17 (based on substrates). By mixing these two purified enzymes, inexpensive racemic styrene oxide (5 mM) was converted at 100% yield to 98% enantiomeric excess (R)-1-phenyl-1,2-ethanediol at 4.7 +/- 0.7 micromol/min/mg. Hence, at least 99% of substrate is converted into a single stereospecific product at a rapid rate.  相似文献   

17.
Purification of a cis-epoxysuccinic acid hydrolase was achieved by ammonium sulfate precipitation, ionic exchange chromatography, hydrophobic interaction chromatography followed by size-exclusion chromatography. The enzyme was purified 177-fold with a yield of 14.4%. The apparent molecular mass of the enzyme was determined to be 33 kDa under denaturing conditions. The optimum pH for enzyme activity was 7.0, and the enzyme exhibited maximum activity at about 45 °C in 50 mM sodium phosphate buffer (pH 7.5). EDTA and o-phenanthrolin inhibited the enzyme activity remarkably, suggesting that the enzyme needs some metal cation to maintain its activity. Results of inductively coupled plasma mass spectrometry analysis indicated that the cis-epoxysuccinic acid hydrolase needs Zn2+ as a cofactor. Eight amino acids sequenced from the N-terminal region of the cis-epoxysuccinic acid hydrolase showed the same sequence as the N-terminal region of the beta subunit of the cis-epoxysuccinic acid hydrolase obtained from Alcaligenes sp.  相似文献   

18.
We performed a directed evolution study with a metagenome-derived epoxide hydrolase (EH), termed Kau2. Homology models of Kau2 were built; we selected one of them and used it as a guide for saturation mutagenesis experiments targeted at specific residues within the large substrate binding pocket. During the molecular evolution process, we found several enzyme variants with higher enantioselectivity or enhanced enantioconvergence toward para-Chlorostyrene oxide. Improved enantioselectivities by up to a factor of 5, reaching an E-value of up to 130 with the R-enantiomer as the residual epoxide, were achieved by replacing amino acid pairs at the positions 110 and 113, or 290 and 291, which are positions located in the vicinity of two presumed binding sites for the epoxide enantiomers. The (R)-para-Chlorophenylethane-1,2-diol product exhibited a high enantiomeric excess (ee) of 97% at 50% conversion of the racemic epoxide for the most enantioselective variant. Further, five amino acid substitutions were sufficient to substantially increase the degree of enantioconvergence and to lower the E-value to 17 for the final evolved EH variant, enabling the production of the R-diol with an ee-value of 93% at 28 °C in a complete conversion of the racemic epoxide. Higher eep-values of up to 97% were determined in enantioconvergent reactions using lower temperatures. The EH activities of whole cells were found to be within the range of 74–125% of the wild-type activity for all investigated variants. We show in this report that the metagenome-derived Kau2 EH is amenable to the redesign of its enantioselectivity and regioselectivity properties by directed evolution using a homology model as a guide. The generated enzyme variants should be useful for the production of the chiral building blocks (R)-para-Chlorostyrene oxide and (R)-para-Chlorophenylethane-1,2-diol.  相似文献   

19.
Prokaryotic dioxygenase is known to catalyze aromatic compounds into their corresponding cis-dihydrodiols without the formation of an epoxide intermediate. Biphenyl dioxygenase from Pseudomonas pseudoalcaligenes KF707 showed novel monooxygenase activity by converting 2(R)- and 2(S)-flavanone to their corresponding epoxides (2-(7-oxabicyclo[4.1.0]hepta-2,4-dien-2-yl)-2, 3-dihydro-4H-chromen-4-one), whereby the epoxide bond was formed between C2′ and C3′ on the B ring of the flavanone. The enzyme also converted 6-hydroxyflavanone and 7-hydroxyflavanone, which do not contain a hydroxyl group on the B-ring, to their corresponding epoxides. In a previous report (S.-Y. Kim, J. Jung, Y. Lim, J.-H. Ahn, S.-I. Kim, and H.-G. Hur, Antonie Leeuwenhoek 84:261-268, 2003), however, we found that the same enzyme showed dioxygenase activity toward flavone, resulting in the production of flavone cis-2′,3′-dihydrodiol. Extensive structural identification of the metabolites of flavanone by using high-pressure liquid chromatography, liquid chromatography/mass spectrometry, and nuclear magnetic resonance confirmed the presence of an epoxide functional group on the metabolites. Epoxide formation as the initial activation step of aromatic compounds by oxygenases has been reported to occur only by eukaryotic monooxygenases. To the best of our knowledge, biphenyl dioxygenase from P. pseudoalcaligenes KF707 is the first prokaryotic enzyme detected that can produce an epoxide derivative on the aromatic ring structure of flavanone.  相似文献   

20.
A newly isolated Bacillus megaterium with epoxide hydrolase activity resolved racemic glycidyl (o, m, p)-methylphenyl ethers to give enantiopure epoxides in 84–99% enantiomeric excess and with 21–73 enantiomeric ratios. The (S)-enantiomer was obtained from rac-glycidyl (o or m)-methylphenyl ether while the (R)-epoxides was obtained from glycidyl p-methylphenyl ether. The observations are explained at the level by enzyme-substrate docking studies.  相似文献   

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