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Marianne Graber - One of the best experts on this subject based on the ideXlab platform.
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Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme Enantioselectivity
Journal of Molecular Catalysis B: Enzymatic, 2010Co-Authors: Zsuzsanna Marton, Valérie Léonard, Sylvain Lamare, Karl Hult, Per-olof Syren, Cédric Bauer, Vinh Tran, Marianne GraberAbstract:Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme Enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled Enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of Enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site.
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Understanding water effect on Candida antarctica lipase B activity and Enantioselectivity towards secondary alcohols.
Journal of Molecular Catalysis B: Enzymatic, 2009Co-Authors: Valérie Léonard, Sylvain Lamare, Karl Hult, Z. Marton, Marianne GraberAbstract:The effect of water activity (aW) on Candida antarctica lipase B (CALB) activity and Enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate, were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB, were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aW was defined. The data showed a pronounced aW effect on both activity and Enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aW increased Enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aW, water decreased Enantioselectivity, due to an unfavourable increase of the entropic term TR-SS‡ of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aW allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.
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A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances the Enantioselectivity towards 2-pentanol
ChemBioChem, 2007Co-Authors: Valérie Léonard, Linda Fransson, Sylvain Lamare, Karl Hult, Marianne GraberAbstract:The effect of water activity on enzyme catalyzed enantioselective transesterification was studied using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was esterification of 2-pentanol with methyl propanoate as acyl donor and lipase B from Candida antarctica as catalyst. Experimental data showed a pronounced water activity effect on both reaction rate and Enantioselectivity. The Enantioselectivity increased from 100 at water activity close to 0 to reach a maximum of 320 at water activity 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slow reacting enantiomer. Measurements of Enantioselectivity at different water activity and temperature showed that the water molecule had a high affinity to the stereospecificity pocket of the active site with a binding energy of 9 kJ mol-1 and lost all its degrees of rotation, corresponding to an entropic energy of 37 J mol-1 K-1.
Karl Hult - One of the best experts on this subject based on the ideXlab platform.
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Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme Enantioselectivity
Journal of Molecular Catalysis B: Enzymatic, 2010Co-Authors: Zsuzsanna Marton, Valérie Léonard, Sylvain Lamare, Karl Hult, Per-olof Syren, Cédric Bauer, Vinh Tran, Marianne GraberAbstract:Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme Enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled Enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of Enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site.
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Understanding water effect on Candida antarctica lipase B activity and Enantioselectivity towards secondary alcohols.
Journal of Molecular Catalysis B: Enzymatic, 2009Co-Authors: Valérie Léonard, Sylvain Lamare, Karl Hult, Z. Marton, Marianne GraberAbstract:The effect of water activity (aW) on Candida antarctica lipase B (CALB) activity and Enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate, were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB, were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aW was defined. The data showed a pronounced aW effect on both activity and Enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aW increased Enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aW, water decreased Enantioselectivity, due to an unfavourable increase of the entropic term TR-SS‡ of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aW allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.
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A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances the Enantioselectivity towards 2-pentanol
ChemBioChem, 2007Co-Authors: Valérie Léonard, Linda Fransson, Sylvain Lamare, Karl Hult, Marianne GraberAbstract:The effect of water activity on enzyme catalyzed enantioselective transesterification was studied using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was esterification of 2-pentanol with methyl propanoate as acyl donor and lipase B from Candida antarctica as catalyst. Experimental data showed a pronounced water activity effect on both reaction rate and Enantioselectivity. The Enantioselectivity increased from 100 at water activity close to 0 to reach a maximum of 320 at water activity 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slow reacting enantiomer. Measurements of Enantioselectivity at different water activity and temperature showed that the water molecule had a high affinity to the stereospecificity pocket of the active site with a binding energy of 9 kJ mol-1 and lost all its degrees of rotation, corresponding to an entropic energy of 37 J mol-1 K-1.
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Improved Enantioselectivity of a lipase by rational protein engineering.
Chembiochem : a European journal of chemical biology, 2001Co-Authors: Didier Rotticci, Johanna C. Rotticci-mulder, Stuart E. Denman, Torbjörn Norin, Karl HultAbstract:A model based on two different binding modes for alcohol enantiomers in the active site of a lipase allowed rational redesign of its Enantioselectivity, 1-Halo-2-octanols were poorly resolved by Candida antarctica lipase B. Interactions between the substrates and the lipase were investigated with molecular modeling. Unfavorable interactions were found between the halogen moiety of the fast-reacting S enantiomer and a region situated at the bottom of the active site (stereoselectivity pocket). The lipase was virtually mutated in this region and energy contour maps of some variants displayed better interactions for the target substrates. Four selected variants of the lipase were produced and kinetic resolution experiments were undertaken with these mutants. Single point mutants gave rise to one variant with doubled Enantioselectivity as well as one variant with annihilated Enantioselectivity towards the target halohydrins. An increased volume of the stereoselectivity pocket caused a decrease in Enantioselectivity, while changes in electrostatic potential increased Enantioselectivity, The Enantioselectivity of these new lipase variants towards other types of alcohols was also investigated. The changes in Enantioselectivity caused by the mutations were well in agreement with the proposed model concerning the chiral recognition of alcohol enantiomers by this lipase.
Valérie Léonard - One of the best experts on this subject based on the ideXlab platform.
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Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme Enantioselectivity
Journal of Molecular Catalysis B: Enzymatic, 2010Co-Authors: Zsuzsanna Marton, Valérie Léonard, Sylvain Lamare, Karl Hult, Per-olof Syren, Cédric Bauer, Vinh Tran, Marianne GraberAbstract:Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme Enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled Enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of Enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site.
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Understanding water effect on Candida antarctica lipase B activity and Enantioselectivity towards secondary alcohols.
Journal of Molecular Catalysis B: Enzymatic, 2009Co-Authors: Valérie Léonard, Sylvain Lamare, Karl Hult, Z. Marton, Marianne GraberAbstract:The effect of water activity (aW) on Candida antarctica lipase B (CALB) activity and Enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate, were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB, were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aW was defined. The data showed a pronounced aW effect on both activity and Enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aW increased Enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aW, water decreased Enantioselectivity, due to an unfavourable increase of the entropic term TR-SS‡ of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aW allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.
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A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances the Enantioselectivity towards 2-pentanol
ChemBioChem, 2007Co-Authors: Valérie Léonard, Linda Fransson, Sylvain Lamare, Karl Hult, Marianne GraberAbstract:The effect of water activity on enzyme catalyzed enantioselective transesterification was studied using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was esterification of 2-pentanol with methyl propanoate as acyl donor and lipase B from Candida antarctica as catalyst. Experimental data showed a pronounced water activity effect on both reaction rate and Enantioselectivity. The Enantioselectivity increased from 100 at water activity close to 0 to reach a maximum of 320 at water activity 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slow reacting enantiomer. Measurements of Enantioselectivity at different water activity and temperature showed that the water molecule had a high affinity to the stereospecificity pocket of the active site with a binding energy of 9 kJ mol-1 and lost all its degrees of rotation, corresponding to an entropic energy of 37 J mol-1 K-1.
Sylvain Lamare - One of the best experts on this subject based on the ideXlab platform.
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Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme Enantioselectivity
Journal of Molecular Catalysis B: Enzymatic, 2010Co-Authors: Zsuzsanna Marton, Valérie Léonard, Sylvain Lamare, Karl Hult, Per-olof Syren, Cédric Bauer, Vinh Tran, Marianne GraberAbstract:Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme Enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled Enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of Enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site.
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Understanding water effect on Candida antarctica lipase B activity and Enantioselectivity towards secondary alcohols.
Journal of Molecular Catalysis B: Enzymatic, 2009Co-Authors: Valérie Léonard, Sylvain Lamare, Karl Hult, Z. Marton, Marianne GraberAbstract:The effect of water activity (aW) on Candida antarctica lipase B (CALB) activity and Enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate, were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB, were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aW was defined. The data showed a pronounced aW effect on both activity and Enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aW increased Enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aW, water decreased Enantioselectivity, due to an unfavourable increase of the entropic term TR-SS‡ of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aW allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.
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A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances the Enantioselectivity towards 2-pentanol
ChemBioChem, 2007Co-Authors: Valérie Léonard, Linda Fransson, Sylvain Lamare, Karl Hult, Marianne GraberAbstract:The effect of water activity on enzyme catalyzed enantioselective transesterification was studied using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was esterification of 2-pentanol with methyl propanoate as acyl donor and lipase B from Candida antarctica as catalyst. Experimental data showed a pronounced water activity effect on both reaction rate and Enantioselectivity. The Enantioselectivity increased from 100 at water activity close to 0 to reach a maximum of 320 at water activity 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slow reacting enantiomer. Measurements of Enantioselectivity at different water activity and temperature showed that the water molecule had a high affinity to the stereospecificity pocket of the active site with a binding energy of 9 kJ mol-1 and lost all its degrees of rotation, corresponding to an entropic energy of 37 J mol-1 K-1.
Yoshiaki Nishibayashi - One of the best experts on this subject based on the ideXlab platform.
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remarkable effect of n substituent on enantioselective ruthenium catalyzed propargylation of indoles with propargylic alcohols
Organic Letters, 2007Co-Authors: Hiroshi Matsuzawa, Keiichiro Kanao, Yoshihiro Miyake, Yoshiaki NishibayashiAbstract:Ruthenium-catalyzed enantioselective propargylation of indoles with propargylic alcohols affords the corresponding β-propargylated indoles in good yields with a high Enantioselectivity (up to 95% ee). A remarkable effect of the nature of the N-substituent of indoles is observed for the Enantioselectivity of the propargylated indoles. The preparative method described in this paper may provide a novel protocol for asymmetric Friedel−Crafts alkylation of indoles using propargylic alcohols as a new type of electrophiles.
