EFFECTS OF AMPHIPATHS ON THE ACTIVITY AND STABILITY OF FUSARIUM-SOLANI PISI CUTINASE

The effects of sodium dodecylsulfate (SDS) and Triton X-100 on the sta bility 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 intermediat e that could be reversibly activated by Triton X-100. The intermediate is long lived Out unstable, degrading more slowly to an irreversibly inactivated material. Degradation of native enzyme as well as the inte rmediate follows first-order kinetics. At concentrations below 1 mM, S DS carried an increase in K-m with little effect on V-max for PNPV res ulting in reduction in the second-order rate constant. An increase in the second-order rate constant for phosphorylation by diethyl p-nitrop henylphosphate (E600) was observed with increasing SDS concentrations. These data suggest SDS causes local conformational changes in the act ive site that result in inhibition partial reversible unfolding, and s ubsequent inactivation. (C) 1998 Elsevier Science Inc.