Menthyl acetate is a natural monoterpene which contributes to the smell and flavor of peppermint. It is the acetate ester of menthol. Menthyl acetate constitutes 3-5% of the volatile oil of mentha piperita
Esterases receive special attention because their wide distribution in biological systems and environments and their importance for physiology and chemical synthesis. The prediction of esterases substrate promiscuity level from sequence data and the molecular reasons why certain such enzymes are more promiscuous than others, remain to be elucidated. This limits the surveillance of the sequence space for esterases potentially leading to new versatile biocatalysts and new insights into their role in cellular function. Here we performed an extensive analysis of the substrate spectra of 145 phylogenetically and environmentally diverse microbial esterases, when tested with 96 diverse esters. We determined the primary factors shaping their substrate range by analyzing substrate range patterns in combination with structural analysis and protein-ligand simulations. We found a structural parameter that helps ranking (classifying) promiscuity level of esterases from sequence data at 94% accuracy. This parameter, the active site effective volume, exemplifies the topology of the catalytic environment by measuring the active site cavity volume corrected by the relative solvent accessible surface area (SASA) of the catalytic triad. Sequences encoding esterases with active site effective volumes (cavity volume/SASA) above a threshold show greater substrate spectra, which can be further extended in combination with phylogenetic data. This measure provides also a valuable tool for interrogating substrates capable of being converted. This measure, found to be transferred to phosphatases of the haloalkanoic acid dehalogenase superfamily and possibly other enzymatic systems, represents a powerful tool for low-cost bioprospecting for esterases with broad substrate ranges, in large scale sequence datasets.
        
Title: Efficient kinetic resolution of (+/-)-menthol by a lipase from Thermomyces lanuginosus De Yan H, Li Q, Wang Z Ref: Biotechnol Appl Biochem, 64:87, 2017 : PubMed
A lipase from Thermomyces lanuginosus (Lipozyme TL IM) exhibited high enantioselectivity for kinetic resolution of (+/-)-menthol in organic solvent. The various reaction parameters affecting the conversion and enantioselectivity were studied. The optimum reaction conditions for the transesterification reaction were found with vinyl acetate in the solvent of methyl tert-butyl ether with a vinyl acetate:(+/-)-menthol molar ratio of 5:1 and an enzyme concentration of 200 g/L at 30 degreeC. In these conditions, (-)-menthyl acetate with 99.3% enantiomeric excess was obtained, whereas the conversion was 34.7% with the reaction time of 12 H at the substrate concentration of 0.5 M. In addition, the enzyme allowed the substrate loading to be increased up to 1.5 M without the decrease of the enantioselectivity. These results indicated that Lipozyme TL IM was a promising biocatalyst in the resolution of (+/-)-menthol.
Herein, we applied a community genomic approach using a naphthalene-enriched community (CN1) to isolate a versatile esterase (CN1E1) from the alpha/beta-hydrolase family. The protein shares low-to-medium identity (</= 57%) with known esterase/lipase-like proteins. The enzyme is most active at 25-30 degrees C and pH 8.5; it retains approximately 55% of its activity at 4 degrees C and less than 8% at >/= 55 degrees C, which indicates that it is a cold-adapted enzyme. CN1E1 has a distinct substrate preference compared with other alpha/beta-hydrolases because it is catalytically most active for hydrolysing polyaromatic hydrocarbon (phenanthrene, anthracene, naphthalene, benzoyl, protocatechuate and phthalate) esters (7200-21 000 units g-1 protein at 40 degrees C and pH 8.0). The enzyme also accepts 44 structurally different common esters with different levels of enantio-selectivity (1.0-55 000 units g-1 protein), including (+/-)-menthyl-acetate, (+/-)-neomenthyl acetate, (+/-)-pantolactone, (+/-)-methyl-mandelate, (+/-)-methyl-lactate and (+/-)-glycidyl 4-nitrobenzoate (in that order). The results provide the first biochemical evidence suggesting that such broad-spectrum esterases may be an ecological advantage for bacteria that mineralize recalcitrant pollutants (including oil refinery products, plasticizers and pesticides) as carbon sources under pollution pressure. They also offer a new tool for the stereo-assembly (i.e. through ester bonds) of multi-aromatic molecules with benzene rings that are useful for biology, chemistry and materials sciences for cases in which enzyme methods are not yet available.
Esterase/lipase-catalyzed selective hydrolysis of d, l-menthyl esters has become one of the promising approaches for producing l-menthol, one of the most important flavoring chemicals with extensive uses. However, the activity and l-enantioselectivity of the biocatalyst are not sufficient for meeting the industrial requirements. Herein, a highly active para-nitrobenzyl esterase from Bacillus subtilis 168 (pnbA-BS) was cloned and then engineered to enhance its l-enantioselectivity. On the basis of the strategy tailoring the steric exclusion effect and structural flexibility of the region adjacent to the substrate, the substitution of Ala400 to Pro caused a remarkable improvement in the E value from 1.0 to 466.6. The variant A400P was purified and further confirmed with strict l-enantioselectivity in the selective hydrolysis of d, l-menthyl acetate, whereas the improved l-enantioselectivity caused decreased activity. To develop an efficient, easy-to-use, and green methodology, organic solvent was omitted and substrate constant feeding was integrated into the whole-cell catalyzed system. During the catalytic process, the selective hydrolysis of 1.0 M d, l-menthyl acetate in 14 h offered a conversion of 48.9%, e.e.(p) value of >99%, and space-time yield of 160.52 g (l d)(-1).
Esterases receive special attention because their wide distribution in biological systems and environments and their importance for physiology and chemical synthesis. The prediction of esterases substrate promiscuity level from sequence data and the molecular reasons why certain such enzymes are more promiscuous than others, remain to be elucidated. This limits the surveillance of the sequence space for esterases potentially leading to new versatile biocatalysts and new insights into their role in cellular function. Here we performed an extensive analysis of the substrate spectra of 145 phylogenetically and environmentally diverse microbial esterases, when tested with 96 diverse esters. We determined the primary factors shaping their substrate range by analyzing substrate range patterns in combination with structural analysis and protein-ligand simulations. We found a structural parameter that helps ranking (classifying) promiscuity level of esterases from sequence data at 94% accuracy. This parameter, the active site effective volume, exemplifies the topology of the catalytic environment by measuring the active site cavity volume corrected by the relative solvent accessible surface area (SASA) of the catalytic triad. Sequences encoding esterases with active site effective volumes (cavity volume/SASA) above a threshold show greater substrate spectra, which can be further extended in combination with phylogenetic data. This measure provides also a valuable tool for interrogating substrates capable of being converted. This measure, found to be transferred to phosphatases of the haloalkanoic acid dehalogenase superfamily and possibly other enzymatic systems, represents a powerful tool for low-cost bioprospecting for esterases with broad substrate ranges, in large scale sequence datasets.
        
Title: Efficient kinetic resolution of (+/-)-menthol by a lipase from Thermomyces lanuginosus De Yan H, Li Q, Wang Z Ref: Biotechnol Appl Biochem, 64:87, 2017 : PubMed
A lipase from Thermomyces lanuginosus (Lipozyme TL IM) exhibited high enantioselectivity for kinetic resolution of (+/-)-menthol in organic solvent. The various reaction parameters affecting the conversion and enantioselectivity were studied. The optimum reaction conditions for the transesterification reaction were found with vinyl acetate in the solvent of methyl tert-butyl ether with a vinyl acetate:(+/-)-menthol molar ratio of 5:1 and an enzyme concentration of 200 g/L at 30 degreeC. In these conditions, (-)-menthyl acetate with 99.3% enantiomeric excess was obtained, whereas the conversion was 34.7% with the reaction time of 12 H at the substrate concentration of 0.5 M. In addition, the enzyme allowed the substrate loading to be increased up to 1.5 M without the decrease of the enantioselectivity. These results indicated that Lipozyme TL IM was a promising biocatalyst in the resolution of (+/-)-menthol.
Herein, we applied a community genomic approach using a naphthalene-enriched community (CN1) to isolate a versatile esterase (CN1E1) from the alpha/beta-hydrolase family. The protein shares low-to-medium identity (</= 57%) with known esterase/lipase-like proteins. The enzyme is most active at 25-30 degrees C and pH 8.5; it retains approximately 55% of its activity at 4 degrees C and less than 8% at >/= 55 degrees C, which indicates that it is a cold-adapted enzyme. CN1E1 has a distinct substrate preference compared with other alpha/beta-hydrolases because it is catalytically most active for hydrolysing polyaromatic hydrocarbon (phenanthrene, anthracene, naphthalene, benzoyl, protocatechuate and phthalate) esters (7200-21 000 units g-1 protein at 40 degrees C and pH 8.0). The enzyme also accepts 44 structurally different common esters with different levels of enantio-selectivity (1.0-55 000 units g-1 protein), including (+/-)-menthyl-acetate, (+/-)-neomenthyl acetate, (+/-)-pantolactone, (+/-)-methyl-mandelate, (+/-)-methyl-lactate and (+/-)-glycidyl 4-nitrobenzoate (in that order). The results provide the first biochemical evidence suggesting that such broad-spectrum esterases may be an ecological advantage for bacteria that mineralize recalcitrant pollutants (including oil refinery products, plasticizers and pesticides) as carbon sources under pollution pressure. They also offer a new tool for the stereo-assembly (i.e. through ester bonds) of multi-aromatic molecules with benzene rings that are useful for biology, chemistry and materials sciences for cases in which enzyme methods are not yet available.