Reference : Psychrophilic Enzymes: Revisiting the Thermodynamic Parameters of Activation May Expl...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
Psychrophilic Enzymes: Revisiting the Thermodynamic Parameters of Activation May Explain Local Flexibility
Lonhienne, T. [> > > >]
Gerday, Charles mailto [Université de Liège - ULiège > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]
Feller, Georges mailto [Université de Liège - ULiège > Département des sciences de la vie > Labo de biochimie >]
Biochimica et Biophysica Acta
Yes (verified by ORBi)
[en] Basic theoretical and practical aspects of activation parameters are briefly reviewed in the context of cold-adaptation. In order to reduce the error impact inherent to the transition state theory on the absolute values of the free energy (DeltaG(#)), enthalpy (DeltaH(#)) and entropy (DeltaS(#)) of activation, it is proposed to compare the variation of these parameters between psychrophilic and mesophilic enzymes, namely Delta(DeltaG(#))(p-m), Delta(DeltaH(#))(p-m) and Delta(DeltaS(#))(p-m). Calculation of these parameters from the available literature shows that the main adaptation of psychrophilic enzymes lies in a significant decrease of DeltaH(#), therefore leading to a higher k(cat), especially at low temperatures. Moreover, in all cases including cold-blooded animals, DeltaS(#) exerts an opposite and negative effect on the gain in k(cat). It is argued that the magnitude of this counter-effect of DeltaS(#) can be reduced by keeping some stable domains, while increasing the flexibility of the structures required to improve catalysis at low temperature, as demonstrated in several cold-active enzymes. This enthalpic-entropic balance provides a new approach explaining the two types of conformational stability detected by recent microcalorimetric experiments on psychrophilic enzymes.

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