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Solvent effect on lipase enantioselectivity. Evidence for the presence of two thermodynamic states
Author(s) -
Overbeeke P. L. Antoine,
Jongejan J. A.,
Heijnen J. J.
Publication year - 2000
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/1097-0290(20001105)70:3<278::aid-bit5>3.0.co;2-i
Subject(s) - chemistry , solvent , enthalpy , thermodynamics , solvent effects , additive function , kinetic energy , lipase , composition (language) , organic chemistry , enzyme , physics , mathematical analysis , linguistics , philosophy , mathematics , quantum mechanics
The enantioselectivity of lipase‐catalyzed kinetic resolutions has been measured at various temperatures in binary mixtures of solvents. Varying the solvent composition and temperature had a profound effect on the enantiomeric ratio. The values for ΔΔ H R–S #and ΔΔ S # R–S , calculated from the E values measured at various temperatures, were estimated as a function of the solvent composition. By plotting ΔΔ H R–S #versus ΔΔ S R–S #as a function of the solvent composition, an extreme was observed. The resulting “hairpin‐type” enthalpy–entropy compensation plots can be described by assuming the presence of two thermodynamically distinct physical states, displaying different enantioselectivities, that are in equilibrium with one another. Changing the solvent composition results in a change in the equilibrium constant K eq for the two states. The intriguing bell‐shaped curves of the enantioselectivity versus solvent composition observed for lipase‐catalyzed kinetic resolutions can be described assuming a linear correlation for the logarithm of K eq and the solvent composition. Thus, a simulation of the two‐state model adequately describes the solvent effects found for lipase‐catalyzed kinetic resolutions in binary mixtures of solvents and possibly in series of homologous organic solvents. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 70: 278–290, 2000.