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Extremophiles (2008) 12:5159 DOI 10.1007/s00792-007-0089-7
REVIEW
The effect of temperature on enzyme activity: new insights and their implications
Roy M. Daniel Michael J. Danson Robert Eisenthal Charles K. Lee Michelle E. Peterson
Received: 21 January 2007 / Accepted: 19 April 2007 / Published online: 13 September 2007 Springer 2007
Abstract The two established thermal properties of enzymes are their activation energy and their thermal stability. Arising from careful measurements of the thermal behaviour of enzymes, a new model, the Equilibrium Model, has been developed to explain more fully the effects of temperature on enzymes. The model describes the effect of temperature on enzyme activity in terms of a rapidly reversible active-inactive transition, in addition to an irreversible thermal inactivation. Two new thermal parameters, Teq and DHeq, describe the activeinactive transition, and enable a complete description of the effect of temperature on enzyme activity. We review here the Model itself, methods for the determination of Teq and
DHeq, and the implications of the Model for the environmental adaptation and evolution of enzymes, and for biotechnology.
Keywords Equilibrium Model Temperature
Enzyme Adaptation Evolution Temperature optimum
Stability Denaturation Teq DHeq
Introduction
If an enzyme is assayed for a xed duration over a range of temperatures, we observe a plot with an apparent optimum (Fig. 1). This observed optimum temperature is not an intrinsic enzyme property, since it arises from a mixture of thermal properties, and from assay duration. Nevertheless, this behaviour has led to a long-standing implicit assumption of a two-state model (the Classical Model), where the dependence of enzyme activity on temperature can be described by the effect of temperature on two processes: the catalytic reaction, dened by kcat, and irre
versible inactivation (denaturation) dened by kinact. The
temperature dependence of these rate constants is characterised, respectively, by the catalytic activation energy DG cat, and the activation energy for the irreversible inactivation reaction, DG inact.
In this situation the variation in enzyme activity with temperature and time of assay can be described as follows:
Vmax kcat E0
e kinact t 1
where Vmax = maximum velocity of enzyme; kcat = enzymes catalytic constant; [E0] = total concentration of enzyme; kinact = thermal inactivation rate constant; t = time.
The variation of the two rate constants in Eq....