Surfactant-induced unfolding of cellulase: kinetic studies

Surfactant-induced unfolding is a significant degradation pathway for detergent enzymes. This study examines the kinetics of surfactant-induced unfolding for endoglucanase III, a detergent cellulase, under conditions of varying pH, temperature, ionic strength, surfactant type, and surfactant concentration. Interactions between protein and surfactant monomer are shown to play a key role in determining the kinetics of the unfolding process. We demonstrate that the unfolding rate can be slowed by (1) modifying protein charge and/or pH conditions to create electrostatic repulsion of ionic surfactants and (2) reducing the amount of monomeric ionic surfactant available for interaction with the enzyme (i.e., by lowering the critical micelle concentration). Additionally, our results illustrate that there is a poor correlation between thermodynamic stability in buffer (DeltaG(unfolding)) and resistance to surfactant-induced unfolding.