Trehalose protects urea-induced unfolding of α-chymotrypsin

Trehalose, a naturally occurring osmolyte, appears to be one of the most effective protectants for enzymes under various stress conditions while urea, a classical denaturant, destabilizes the activity, function, and alters the native structure of proteins. Herein, we have characterized the counteracting effects of trehalose on the deleterious effect of urea on alpha-chymotrypsin (CT) through the calorimetric data (transition temperature (T-m), enthalpy change (Delta H), heat capacity change (Delta C-p) and Gibbs free energy of unfolding (Delta G(u)) by using differential scanning calorimeter (DSC) and circular dichroism (CD) techniques, respectively, at a 1:2 ratio of trehalose and urea, as well as various urea concentration (up to 6 M) in the presence of 1 M trehalose. Our parallel experimental results explicitly elucidate that trehalose strongly offset the deleterious actions of urea on CT at 1:2 molar ratio of trehalose and urea, however, trehalose (1 M) some how failed to counteract the perturbation effects of urea (3-6 M) on CT. (C) 2010 Elsevier B.V. All rights reserved.