Lysozyme activity in the presence of nonionic detergent micelles

The effect of a nonionic surfactant, polyoxyethylenesorbitan monolaurate (Tween 20), on the hen egg‐white lysozyme catalyzed lysis of a dried cell suspension of Micrococcus lysodeikticus is analysed. A rate enhancement of up to 70% is observed in the presence of surfactant at concentrations above the critical micelle concentration. This activity increase may be explained by postulating the existence of a micelle‐enzyme complex in which enzyme molecules are bound to micelles with preferential orientation of their active sites. The reaction is found to be second order with respect to substrate. A mechanism is postulated in which a substrate particle is assumed to be an energy‐furnishing collision partner to the enzyme‐substrate complex. This mechanism correlated data over a wide range of enzyme and substrate concentrations. Data from kinetic, ultrafiltration, ultraviolet, and fluorescence studies provide convincing evidence for the existence of a micelle‐lysozyme complex. The results suggest that it is possible that immobilized enzymes mat in general be more reactive than corresponding free enzymes.