Enthalpic and entropic contributions to lipase enantioselectivity

The enantioselective properties of lipases in the kinetic resolution of chiral substrates are conveniently expressed as the enantiomeric ratio, E. It has been stated that E is related to the difference of the Gibbs free energy of activation of the enantioselective reaction steps by RT ln E=−ΔΔ G #=...

Full description

Saved in:

Bibliographic Details
Published in:	Chemistry and physics of lipids Vol. 93; no. 1; pp. 81 - 93
Main Authors:	Overbeeke, P.L.Antoine, Orrenius, S.Christian, Jongejan, Jaap A, Duine, Johannis A
Format:	Journal Article
Language:	English
Published:	Elsevier Ireland Ltd 01-06-1998
Subjects:	Enantioselectivity Enthalpy–entropy compensation Lipases Organic media Two-state models Two-state models APS, Amano PS lipase Enthalpy–entropy compensation EEC, Enthalpy–entropy compensation Enantioselectivity PFL, Pseudomonas fluorescens lipase CRL, Candida rugosa lipase E, Enantiomeric ratio AMY, Amano MY TST, Transition state theory Lipases Organic media solketal, 2,2-dimethyl-4-(hydroxymethyl)-1,3-dioxolane
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	The enantioselective properties of lipases in the kinetic resolution of chiral substrates are conveniently expressed as the enantiomeric ratio, E. It has been stated that E is related to the difference of the Gibbs free energy of activation of the enantioselective reaction steps by RT ln E=−ΔΔ G #= TΔΔ S #−ΔΔ H #. From the temperature dependence of E we estimated the enthalpic, ΔΔ H #, and entropic, ΔΔ S #, contributions. Contrary to earlier suggestions (Åqvist, J. and Warshel, A., 1993. Simulation of enzyme reactions using valence bond force fields and other hybrid quantum/classical approaches. Chem. Rev. 93, 2523–2544.) it is found that the entropic contribution, TΔΔ S #, to lipase enantioselectivity at ordinary temperatures is significant. Plots of ΔΔ H # versus ΔΔ S # for enzyme-catalyzed kinetic resolutions reported in the literature, show a tempting linear correlation of the enthalpic and entropic contributions. On closer inspection, we realized that this is the result of a non-random selection of systems. Hairpin curves are observed for plots of the enthalpic and entropic contributions to lipase-catalyzed enantioselective reactions in water-cosolvent mixtures and in organic media as a function of medium composition. The importance of these findings for the fundamental understanding of enzyme enantioselectivity, the rationalization of solvent effects on the enantiomeric ratio and the prediction of lipase enantioselectivity by molecular modeling techniques is discussed.
ISSN:	0009-3084 1873-2941
DOI:	10.1016/S0009-3084(98)00031-0