Effects of amphipaths on the activity and stability of Fusarium solani pisi cutinase

Abstract The effects of sodium dodecylsulfate (SDS) and Triton X-100 on the stability and activity of cutinase from Fusarium solani pisi were studied using the soluble substrate p -nitrophenylvalerate (PNPV). Incubation of the enzyme with SDS caused the formation of an inactive intermediate that could be reversibly activated by Triton X-100. The intermediate is long lived but unstable, degrading more slowly to an irreversibly inactivated material. Degradation of native enzyme as well as the intermediate follows first-order kinetics. At concentrations below 1 m m , SDS caused an increase in K m with little effect on V max for PNPV resulting in reduction in the second-order rate constant. An increase in the second-order rate constant for phosphorylation by diethyl p -nitrophenylphosphate (E600) was observed with increasing SDS concentrations. These data suggest SDS causes local conformational changes in the active site that result in inhibition, partial reversible unfolding, and subsequent inactivation.