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A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances enantioselectivity towards pentan-2-ol
Univ Rochelle, FRE CNRS 2766, Lab Biotechnol & Chim Bioorgan.
KTH, School of Biotechnology (BIO), Biochemistry.
Univ Rochelle, FRE CNRS 2766, Lab Biotechnol & Chim Bioorgan.
KTH, School of Biotechnology (BIO), Biochemistry.
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2007 (English)In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 8, no 6, 662-667 p.Article in journal (Refereed) Published
Abstract [en]

The effect of water activity on enzyme-catalyzed enantioselective transesterification was studied by using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was the esterification of pentan-2-ol with methylpropanoate as acyl donor and lipase B from Candida antarctica as catalyst. The data showed a pronounced water-activity effect on both reaction rote and enantioselectivity. The enantioselectivity increased from 100, at water activity close to zero, to a maximum of 320, at a water activity of 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slowly reacting enantiomer. Measurements of enantioselectivity at different water-activity values and temperatures showed that the water molecule had a high affinity for the stereospecificity pocket of the active site with a binding energy of 9 kJ mol(-1), and that it lost all its degrees of rotation, corresponding to an entropic energy of 37 Jmol(-1)K(-1).

Place, publisher, year, edition, pages
2007. Vol. 8, no 6, 662-667 p.
Keyword [en]
enantioselectivity, enzyme catalysis, hydrolases, thermodynamics, water
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-14180DOI: 10.1002/cbic.200600479ISI: 000245907100015Scopus ID: 2-s2.0-34250309643OAI: oai:DiVA.org:kth-14180DiVA: diva2:331468
Note
QC 20100722Available from: 2010-07-22 Created: 2010-07-22 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Enzyme substrate solvent interactions: a case study on serine hydrolases
Open this publication in new window or tab >>Enzyme substrate solvent interactions: a case study on serine hydrolases
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Reaction rates and selectivities were measured for transacylation of fatty acid esters in solvents catalysed by Candida antarctica lipase B and by cutinase from Humicola insolens. With these enzymes classical water-based enzymology can be expanded to many different solvents allowing large variations in interaction energies between the enzymes, the substrates and the surrounding. Further ,hydrolysis reactions catalysed by Bacillus subtilis esterase 2 were investigated.

Thermodynamics analyses revealed that the enzyme contribution to reaction rate acceleration compared to acid catalysis was purely entropic. On the other hand, studies of differences in activation entropy and enthalpy between enantiomers and between homologous esters showed that high substrate specificity was favoured by enthalpic stabilisation.

Solvent was found to have a profound effect on enzyme catalysis, affecting both reaction rate and selectivity. Differences in substrate solubility will impact enzyme specificity since substrate binding is an equilibrium between enzyme-bound substrate and substrate in free solution. In addition, solven tmolecules were found to act as enzyme inhibitors, showing both competitive and non-competitive behaviour.

In several homologous data series enthalpy-entropy compensation relationships were encountered. A possible extrathermodynamic relationship between enthalpy and entropy can easily be lost under co-varying errors propagated from the experiments. From the data in this thesis, one instance was found of a real enthalpy-entropy compensation that could be distinguished from statistical errors, while other examples could not be verified.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 43 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2008:15
Keyword
lipase, esterase, specificity
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-4867 (URN)978-91-7415-094-0 (ISBN)
Public defence
2008-09-05, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100722Available from: 2008-09-10 Created: 2008-09-05 Last updated: 2011-07-07Bibliographically approved

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