The Isolation and Characterisation of a Carbocyclic Epoxide-Degrading Corynebacterium sp

A two-phase aqueous/organic isolation system was developed for the isolation of epoxide-degrading bacteria. The potential of this system, for the isolation of cyclohexene oxide-degrading bacteria, was assessed by comparison to an analogous system lacking co-solvent. Using the biphasic isolation strategy, an epoxide-degrading Corynebacterium sp. designated C12, was isolated and was shown to grow on cyclohexene oxide as sole source of carbon and energy. Epoxide degradation appeared to proceed via a diol intermediate implicating the involvement of an epoxide hydrolase. The epoxide hydrolase of Corynebacterium sp. C12 was shown to have activity towards a range of terminal, sub-terminal and cyclic substrates. The enantioselectivity of the hydrolysis reaction was largely dependent on the nature of the substrate. In a series of biotransformations allowed to proceed to 50% substrate conversion, the remaining epoxide ranged from low (5% ee) to moderate (60% ee) optical purity.     

Kinetic resolution for optically active epoxides by microbial enantioselective hydrolysis

Resolution of several racemic epoxides was accomplished using an epoxide hydrolase activity of whole cells of the newly isolated Aspergillus niger. (S)-Styrene oxide, for example, was obtained from its racemates with optical purity of 100% ee and 32% yield. © Rapid Science Ltd. 1998     

Cytosolic and microsomal epoxide hydrolases are immunologically distinguishable from each other in the rat and mouse

Antibodies raised to homogeneous rat liver microsomal epoxide hydrolase were used to distinguish microsomal epoxide hydrolase from epoxide hydrolase of cytosolic origin in mice and rats. Using double diffusion analysis in agarose gels, we show that anti-rat liver microsomal epoxide hydrolase forms a single precipitin line with solubilized microsomes from rat and mouse liver, but no reaction is seen with the corresponding cytosolic fractions. Rat or mouse microsomal epoxide hydrolase activity (using benzo[a]pyrene 4,5-oxide as substrate) can be completely precipitated out of solubilized preparations by the antibody, which is equipotent against rat and mouse microsomal epoxide hydrolase. No precipitation of cytosolic hydrolase activity (using trans-beta-ethyl styrene oxide as substrate) is seen with any concentration of the antibody tested. Thus, in the case of microsomal epoxide hydrolase, extensive immunological cross-reactivity exists between the two species, rat and mouse. In contrast, no cross-reactivity is detectable between cytosolic and microsomal epoxide hydrolase, even when enzymes from the same species are compared. We conclude that microsomal and cytosolic epoxide hydrolase activities represent distinct and immunologically non-cross-reactive protein species.     

The effects of metyrapone, chalcone epoxide, benzil, clotrimazole and related compounds on the activity of microsomal epoxide hydrolase in situ, in purified form and in reconstituted systems towards different substrates

The influence of metyrapone, chalcone epoxide, benzil and clotrimazole on the activity of microsomal epoxide hydrolase towards styrene oxide, benzo[a]pyrene 4,5-oxide, estroxide and androstene oxide was investigated. The studies were performed using liver microsomes from rats, rabbits, mice and humans; epoxide hydrolase purified from rat liver microsomes to apparent homogeneity; and the purified enzyme incorporated into liposomes composed of egg-yolk phosphatidylcholine or total rat liver microsomal lipids. All four effectors were found to activate the hydrolysis of styrene oxide by epoxide hydrolase in situ in rat liver microsomal membranes, in agreement with earlier findings. Epoxide hydrolase activity towards styrene oxide in liver microsomes from mouse, rabbit and man was also increased by all four effectors. The most striking effect was a 680% activation by clotrimazole in rat liver microsomes. However, none of the effectors activated microsomal epoxide hydrolase more than 50% when benzo[a]pyrene 4,5-oxide, estroxide or androstene oxide was used as substrate. Indeed, clotrimazole was found to inhibit microsomal epoxide hydrolase activity towards estroxide 30-50% and towards androstene oxide 60-90%. The effects of these four compounds were found to be virtually identical in the preparations from rats, rabbits, mice and humans. The effects of metyrapone, chalcone epoxide, benzil and clotrimazole on purified epoxide hydrolase were qualitatively the same as those on epoxide hydrolase in intact microsomes, but much smaller in magnitude. These effects were increased in magnitude only slightly by incorporation of the purified enzyme into liposomes made from egg-yolk phosphatidylcholine. However, when incorporation into liposomes composed of total microsomal lipids was performed, the effects seen were essentially of the same magnitude as with intact microsomes. When the extent of activation was plotted against effector concentration, three different patterns were found with different effectors. Activation of epoxide hydrolase activity towards styrene oxide by clotrimazole was found to be uncompetitive with the substrate and highly structure specific. On the other hand, inhibition of epoxide hydrolase activity towards androstene oxide by clotrimazole was found to be competitive in microsomes. It is concluded that the marked effects of these four modulators on microsomal epoxide hydrolase activity are due to an interaction with the enzyme protein itself, but that the presence of total microsomal phospholipids allows the maximal expression leading to similar degrees of modulation as those observed in intact microsomes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Affinity purification of cytosolic epoxide hydrolase using derivatized epoxy-activated Sepharose gels

Improved affinity chromatography procedures for the purification of cytosolic epoxide hydrolase are described. An earlier affinity purification method using immobilized 7-methoxycitronellyl thiol (MCT) sporadically produced final enzyme preparations containing major impurities. To eliminate these impurities, we tested alternate ligands, spacer arms, and ligand concentrations. A series of alkyl and aryl thiols coupled to epoxy-activated Sepharose were found to exhibit markedly different binding characteristics as compared with commercially available alkyl- and aryl-Sepharose gels. Using one of these new matrices, benzylthio-Sepharose, cytosolic epoxide hydrolase from mouse liver was purified over 100-fold, appeared homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and was obtained with 60-90% recovery of enzyme activity. The impurities previously observed with the MCT-Sepharose procedure were reduced or eliminated by using an MCT ligand concentration of 5 microequivalents per gram or less. MCT-Sepharose and benzylthio-Sepharose provide rapid and convenient one-step procedures for obtaining purified cytosolic epoxide hydrolase from numerous species and tissues.     

Biocatalytic resolution of nitro-substituted phenoxypropylene oxides with Trichosporon loubierii epoxide hydrolase and prediction of their enantiopurity variation with reaction time

Biocatalytic resolution of 3-(2′-nitrophenoxy)propylene oxide (1a), 3-(3′-nitrophenoxy)propylene oxide (1b) and 3-(4′-nitrophenoxy)propylene oxide (1c) were exploited by using lyophilized cells of yeast Trichosporon loubierii ECU1040 with epoxide hydrolase (EH) activity, which preferentially hydrolyzes (S)-enantiomers of the epoxides (1a–c), yielding (S)-diols and (R)-epoxides. The activity increased as the nitro group in the phenyl ring was shifted from 4′-position (1c) to 2′-position (1a). When the substrate concentration of 1a was increased from 10 to 80 mM, the E-value increased at first, until reaching a peak at 40 mM, and then decreased at higher concentrations (>40 mM). The optically active epoxide (R)-1a was prepared at gram-scale (97% ee, 41% yield). Furthermore, a simple method was developed to predict the enantiomeric excess of substrate (ee_s) at any time of the whole reaction course based on the ee_s value determined at a certain reaction time at a relatively lower substrate concentration. This will be helpful for terminating the reaction at a proper time to get both higher optical purity and higher yield of the remaining epoxides.     

Enzymatic Mechanisms Involved in Phenanthrene Degradation by the White Rot Fungus Pleurotus ostreatus

The enzymatic mechanisms involved in the degradation of phenanthrene by the white rot fungus Pleurotus ostreatus were examined. Phase I metabolism (cytochrome P-450 monooxygenase and epoxide hydrolase) and phase II conjugation (glutathione S-transferase, aryl sulfotransferase, UDP-glucuronosyltransferase, and UDP-glucosyltransferase) enzyme activities were determined for mycelial extracts of P. ostreatus. Cytochrome P-450 was detected in both cytosolic and microsomal fractions at 0.16 and 0.38 nmol min(sup-1) mg of protein(sup1), respectively. Both fractions oxidized [9,10-(sup14)C]phenanthrene to phenanthrene trans-9,10-dihydrodiol. The cytochrome P-450 inhibitors 1-aminobenzotriazole (0.1 mM), SKF-525A (proadifen, 0.1 mM), and carbon monoxide inhibited the cytosolic and microsomal P-450s differently. Cytosolic and microsomal epoxide hydrolase activities, with phenanthrene 9,10-oxide as the substrate, were similar, with specific activities of 0.50 and 0.41 nmol min(sup-1) mg of protein(sup-1), respectively. The epoxide hydrolase inhibitor cyclohexene oxide (5 mM) significantly inhibited the formation of phenanthrene trans-9,10-dihydrodiol in both fractions. The phase II enzyme 1-chloro-2,4-dinitrobenzene glutathione S-transferase was detected in the cytosolic fraction (4.16 nmol min(sup-1) mg of protein(sup-1)), whereas aryl adenosine-3(prm1)-phosphate-5(prm1)-phosphosulfate sulfotransferase (aryl PAPS sulfotransferase) UDP-glucuronosyltransferase, and UDP-glucosyltransferase had microsomal activities of 2.14, 4.25, and 4.21 nmol min(sup-1) mg of protein(sup-1), respectively, with low activity in the cytosolic fraction. However, when P. ostreatus culture broth incubated with phenanthrene was screened for phase II metabolites, no sulfate, glutathione, glucoside, or glucuronide conjugates of phenanthrene metabolites were detected. These experiments indicate the involvement of cytochrome P-450 monooxygenase and epoxide hydrolase in the initial phase I oxidation of phenanthrene to form phenanthrene trans-9,10-dihydrodiol. Laccase and manganese-independent peroxidase were not involved in the initial oxidation of phenanthrene. Although P. ostreatus had phase II xenobiotic metabolizing enzymes, conjugation reactions were not important for the elimination of hydroxylated phenanthrene.     

Comparison of the sex and subcellular distributions, catalytic and immunochemical reactivities of hepatic epoxide hydrolases in seven mammalian species

Sex and species differences in hepatic epoxide hydrolase activities towards cis- and trans-stilbene oxide were examined in common laboratory animals, as well as in monkey and man. In general trans-stilbene oxide was found to be a good substrate for epoxide hydrolase activity in cytosolic fractions, whereas the cis isomer was selectively hydrated by the microsomal fraction (with the exception of man, where the cytosol also hydrated this isomer efficiently). The specific cytosolic epoxide hydrolase activity was highest in mouse, followed by hamster and rabbit. Epoxide hydrolase activity in the crude 'mitochondrial' fraction towards trans-stilbene oxide was also highest in mouse and low in all other species examined. Microsomal epoxide hydrolase activity was highest in monkey, followed by guinea pig, human and rabbit, which all had similar activities. Sex differences were generally small, but where significant, male animals had higher catalytic activities than females of the same species in most cases. Antibodies raised against microsomal epoxide hydrolase purified from rat liver reacted with microsomes from all species investigated, indicating structural conservation of this protein. Antibodies directed towards cytosolic epoxide hydrolase purified from mouse liver reacted only with liver cytosol from mouse and hamster and with the 'mitochondrial' fraction from mouse in immunodiffusion experiments. Immunoblotting also revealed reaction with rat liver cytosol. The cytosolic and 'mitochondrial' epoxide hydrolases in all three mouse strains and in both sexes for each strain were immunochemically identical. The anomalies in human liver epoxide hydrolase activities observed here indicate that no single common laboratory animal is a good model for man with regard to these activities.     

Biocatalytic preparation of (S)-phenyl glycidyl ether using newly isolated Bacillus megaterium ECU1001

A bacterial strain (ECU1001) capable of utilizing phenyl glycidyl ether as sole carbon source and energy source was isolated from soil samples through two steps of screening and was identified as a Bacillus megaterium. The epoxide hydrolase from Bacillus megaterium ECU1001 was biosynthesized in parallel with cell growth and a maximum activity of 31.0 U/l was reached after 30 h of culture when the biomass (DCW) was 9.1 g/l. A temperature of 35°C and pH 8.0 were optimal for the bioconversion. The lyophilized whole cells of Bacillus megaterium ECU1001 could preferentially hydrolyze the (R)-enantiomer of phenyl glycidyl ether, yeilding (S)-epoxide and (R)-diol with high enantioselectivity (E=47.8). The (S)-enantiomer of the epoxide remained in the reaction mixture with >99.5% ee (enantiomeric excess) at a conversion of 55.9%. The substrate concentration could be increased up to 60 mM without affecting the ee and (S)-phenyl glycidyl ether could be obtained with an optical purity of 100% ee and 25.6% yield. Therefore, the method is potentially useful for the preparative resolution of epoxides.     

Properties of enzymes hydrating epoxides in human epidermis and liver

• 1.1. Cytosolic and microsomal epoxide hydrolyzing enzymes of human skin and liver were compared and found to be different.
• 2.2. Epidermal and hepatic cytosolic epoxide hydrolases were different in terms of substrate selectivity, pI, inhibitor sensitivity and affinity Chromatographic properties.
• 3.3. Microsomal epoxide hydrolases had the same pIs but different substrate selectivities.
• 4.4. Cytosolic epoxide hydrolase from adults had higher specific activity than that from neonates or cultured epidermis, but lower activity than adult hepatic enzymes.
• 5.5. The sizes of cytosolic epoxide hydrolase from epidermis and liver were similar and lower than that from cultured fibroblasts.
• 6.6. Cytosolic epoxide hydrolase from all sources shared similar antigenic determinants.

     

X-ray structure of potato epoxide hydrolase sheds light on substrate specificity in plant enzymes

Epoxide hydrolases catalyze the conversion of epoxides to diols. The known functions of such enzymes include detoxification of xenobiotics, drug metabolism, synthesis of signaling compounds, and intermediary metabolism. In plants, epoxide hydrolases are thought to participate in general defense systems. In the present study, we report the first structure of a plant epoxide hydrolase, one of the four homologous enzymes found in potato. The structure was solved by molecular replacement and refined to a resolution of 1.95 A. Analysis of the structure allows a better understanding of the observed substrate specificities and activity. Further, comparisons with mammalian and fungal epoxide hydrolase structures reported earlier show the basis of differing substrate specificities in the various epoxide hydrolase subfamilies. Most plant enzymes, like the potato epoxide hydrolase, are expected to be monomers with a preference for substrates with long lipid-like substituents of the epoxide ring. The significance of these results in the context of biological roles and industrial applications is discussed.     

Purification of hepoxilin epoxide hydrolase from rat liver

Hepoxilin epoxide hydrolase activity was demonstrated in rat liver cytosol using as substrate [1-14C] hepoxilin A3, a recently described hydroxy epoxide derivative of arachidonic acid. The enzyme was isolated and purified to apparent homogeneity using conventional chromatographic procedures resulting in 41-fold purification. The protein eluted during isoelectric focusing at a pI in the 5.3-5.4 range. The specific activity of the purified protein was 1.2 ng/microgram protein/20 min at 37 degrees C. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under denaturing conditions, a molecular mass value of 53 kDa was observed. Using native polyacrylamide gel electrophoresis, enzyme activity corresponded to the main protein band. The purified protein used hepoxilin A3 as preferred substrate converting it to trioxilin A3. The enzyme was marginally active toward other epoxides such as leukotriene A4 and styrene oxide. The Mr, pI, and substrate specificity of the hepoxilin epoxide hydrolase indicate that this enzyme is different from the recently reported leukotriene A4 hydrolase from human erythrocytes and rat and human neutrophils and constitutes a hitherto undescribed form of epoxide hydrolase with specificity toward hepoxilin A3. Tissue screening for enzyme activity revealed that this enzyme is ubiquitous in the rat.     

Enantioselective hydrolysis of racemic styrene oxide by epoxide hydrolase of<Emphasis Type="Italic">Rhodosporidium kratochvilovae</Emphasis> SYU-08

Enantioselective hydrolysis for the production of chiral styrene oxide was investigated using the epoxide hydrolase activity of a newly isolatedRhodosporidium kratochvilovae SYU-08. The effects of reaction prameters—buffer type, pH, temperature, initial substrate concentrations, phenyl-1,2-ethanediol concentrations on hydrolysis rate, and enantioselectivity—were analyzed. Optically active (S)-styrene oxide with an enantiomeric excess higher than 99 % was obtained from its racemate with a yield of 38 % (theoretically 50% maximum yield) from an initial concentration of 80 mM.     

Preparative-scale kinetic resolution of racemic styrene oxide by immobilized epoxide hydrolase

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 24h 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.     

Purification of human liver cytosolic epoxide hydrolase and comparison to the microsomal enzyme

Epoxide hydrolase (EC 3.3.2.3) was purified to electrophoretic homogeneity from human liver cytosol by using hydrolytic activity toward trans-8-ethylstyrene 7,8-oxide (TESO) as an assay. The overall purification was 400-fold. The purified enzyme has an apparent monomeric molecular weight of 58 000, significantly greater than the 50 000 found for human (or rat) liver microsomal epoxide hydrolase or for another TESO-hydrolyzing enzyme also isolated from human liver cytosol. Purified cytosolic TESO hydrolase catalyzes the hydrolysis of cis-8-ethylstyrene 7,8-oxide 10 times more rapidly than does the microsomal enzyme, catalyzes the hydrolysis of TESO and trans-stilbene oxide as rapidly as the microsomal enzyme, but catalyzes the hydrolysis of styrene 7,8-oxide, p-nitrostyrene 7,8-oxide, and naphthalene 1,2-oxide much less effectively than does the microsomal enzyme. Purified cytosolic TESO hydrolase does not hydrolyze benzo[a]pyrene 4,5-oxide, a substrate for the microsomal enzyme. The activities of the purified enzymes can explain the specific activities observed with subcellular fractions. Anti-human liver microsomal epoxide hydrolase did not recognize cytosolic TESO hydrolase in purified form or in cytosol, as judged by double-diffusion immunoprecipitin analysis, precipitation of enzymatic activity, and immunoelectrophoretic techniques. Cytosolic TESO hydrolase and microsomal epoxide hydrolase were also distinguished by peptide mapping. The results provide evidence that physically different forms of epoxide hydrolase exist in different subcellular fractions and can have markedly different substrate specificities.     

Subcellular distribution, catalytic properties and partial purification of epoxide hydrolase in the human adrenal gland

Epoxide hydrolase in human adrenal gland was characterized with respect to catalytic properties and subcellular distribution. With human adrenal microsomes and the substrates styrene-7,8-oxide, cis-stilbene oxide, estroxide and androstene oxide the specific activities were between 1.9 and 19.0 nmol/min/mg protein. With styrene-7,8-oxide as substrate the apparent Km-value was 0.98 mM and the pH optimum was 9.2. Subcellular fractionation revealed that the bulk of the activity was confined to the endoplasmic reticulum. Different compounds known to influence rodent microsomal epoxide hydrolase activity were also tested on the human adrenal enzyme. 1,1,1-Trichloropropene-2,3-oxide (TCPO) and cyclohexene oxide (CHO) inhibited the activity while benzil and clotrimazole stimulated the activity. Partial purification of human adrenal epoxide hydrolase indicates that its molecular weight is about 51 000 and that its concentration relative total protein in the human adrenal microsomes is about 10%.     

Comparison of crude and affinity purified cytosolic epoxide hydrolases from hepatic tissue of control and clofibrate-fed mice

An affinity purification procedure was developed for the cytosolic epoxide hydrolase based upon the selective binding of the enzyme to immobilized methoxycitronellyl thiol. Several elution systems were examined, but the most successful system employed selective elution with a chalcone oxide. This affinity system allowed the purification of the cytosolic epoxide hydrolase activity from livers of both control and clofibrate-fed mice. A variety of biochemical techniques including pH dependence, substrate preference, kinetics, inhibition, amino acid analysis, peptide mapping, Western blotting, analytical isoelectric focusing, and gel permeation chromatography failed to distinguish between the enzymes purified from control and clofibrate-fed animals. The quantitative removal of the cytosolic epoxide hydrolase acting on trans-stilbene oxide from 100,000g supernatants, allowed analysis of remaining activities acting differentially on cis-stilbene oxide and benzo[a]pyrene 4,5-oxide. Such analysis indicated the existence of a novel epoxide hydrolase activity in the cytosol of mouse liver preparations.     

A spectrophotometric method to assay epoxide hydrolase activity.

The Aspergillus niger epoxide hydrolase activity was assayed by spectrophotometric using (rac) p-nitrostryrene oxide (pNSO) as substrate. Both the substrate (pNSO) and the reaction product, p-nitrostryrene diol (pNSD), had a strong absorbance in UV at 280 nm. The assay was based on the measure of the pNSD absorbance of the water phase after extraction of the non-reacted pNSO with a solvent. Among the five solvents tested, chloroform was selected since it extracted more than 99% of the epoxide and only 32% of the produced diol. This extraction yield was independent of the diol and epoxide concentrations and it was fairly reproducible. Using different enzyme amounts, the reaction kinetics were linear for the first 10 min corresponding to degrees of conversion less than 5% for the epoxide. Two controls were run simultaneously, one with the substrate alone (epoxide hydrolysis and non-complete extraction) and one with the enzyme alone (enzyme absorbance at 280 nm). The resulting DeltaOD/min was linear with the amount of enzyme added within a large range from 2 to 80 microg of the EH preparation. The new spectrophotometric assay correlates well with the previous HPLC assay and could be used routinely for an easy and fast evaluation of EH activity. The kinetic parameters of (rac) pNSO hydrolysis by A. niger epoxide hydrolase could be easily determined and K(M) (1.1 mM) compared well with that previously reported (1.0 mM).     

Interspecies differences in the enantioselectivity of epoxide hydrolases in Cryptococcus laurentii (Kufferath) C.E. Skinner and Cryptococcus podzolicus (Bab'jeva & Reshetova) Golubev

Isolates representing Cryptococcus laurentii and Cryptococcus podzolicus, originating from soil of a heathland indigenous to South Africa, were screened for the presence of enantioselective epoxide hydrolases for 2,2-disubstituted epoxides. Epoxide hydrolase activity for the 2,2-disubstituted epoxide (+/-)-2-methyl-2-pentyl oxirane was found to be abundantly present in all isolates. The stereochemistry of the products formed by the epoxide hydrolase enzymes from isolates belonging to the two species (11 isolates representing C. laurentii and 23 isolates representing C. podzolicus) was investigated. The enantiopreferences of the epoxide hydrolases for 2,2-disubstituted epoxides of these two species were found to be opposite. All strains of C. laurentii preferentially hydrolysed the (S)-epoxides while all C. podzolicus isolates preferentially hydrolysed the (R)-epoxides of (+/-)-2,2-disubstituted epoxides. These findings indicate that the stereochemistry of the products formed from 2,2-disubstituted epoxides by the epoxide hydrolase enzymes of these yeasts should be evaluated as additional taxonomic criterion within the genus Cryptococcus. Also, the selectivity of some epoxide hydrolases originating from isolates of C. podzolicus was high enough to be considered for application in biotransformations for the synthesis of enantiopure epoxides and vicinal diols.     

Epoxide hydrolase activity of Chryseomonas luteola for the asymmetric hydrolysis of aliphatic mono-substituted epoxides

Asymmetric hydrolysis of a homologous range of straight chain 1,2-epoxyalkanes was achieved using whole cells of Chryseomonas luteola. Depending on the chain length, hydrolyses of the racemic epoxides afforded optically active epoxides and diols with varying degrees of optical purity. In the case of 1,2-epoxyoctane, the enantiomeric excess of the remaining (S)-epoxide and formed (R)-diol was excellent (ees > 98% and eep = 86%). This is the first report of a bacterial epoxide hydrolase with such unusual enantioselectivity for terminal mono-substituted epoxides bearing no directing group on the chiral C-2 carbon. Benzyl glycidyl ether and the 2,2-disubstituted epoxide, 2-methyl-1,2-epoxyheptane, were hydrolysed, but no enantioselectivity was observed. © Rapid Science Ltd. 1998