Abstract

An equilibrium-kinetic description for the two-stage irreversible thermoinactivation of enzymes (N D I) is examined by using chymotrypsin as a model. The parameter ΔG for enzyme unfolding (N D) and activation free energy for the D I reaction (ΔG#i) were summed to provide an index of enzyme global thermostability (ΔG#; ΔG# = ΔG + ΔG#i). There was good agreement between calculated and experimental global thermostability (i.e. enzyme stability with respect to reversible and irreversible thermoinactivation reaction steps) at 0–60°C. The results indicate that enzyme global thermostability may be markedly dependent on the rate of enzyme folding