Enthalpy–entropy compensation and the isokinetic temperature in enzyme catalysis
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Enthalpy–entropy compensation supposes that differences in activation enthalpy ∆H ‡ for different reactions (or, typically in biochemistry, the same reaction catalysed by enzymes obtained from different species) may be compensated for by differences in activation entropy ∆S ‡. At the isokinetic temperature the compensation is exact, so that all samples have the same activity. These ideas have been controversial for several decades, but examples are still frequently reported as evidence of a real phenomenon, nearly all of the reports ignoring or discounting the possibility of a statistical artefact. Even for measurements in pure chemistry artefacts occur often, and they are almost inescapable in enzyme kinetics and other fields that involve biological macromolecules, on account of limited stability and the fact that kinetic equations are normally valid only over a restricted range of temperature. Here I review the current status and correct an error in a recent book chapter.
KeywordsArrhenius equation compensation enthalpy entropy isokinetic temperature
This work was supported by Centre National de la Recherche Scientifique and by Aix-Marseille Université. I thank María Luz Cárdenas for useful discussions and Mark Bushuev for shedding helpful light on his paper on spin transitions in an Fe(II) complex.
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