Effects of ionic surfactants used in reversed micelles on cutinase activity and stability

The effects of aqueous surfactant solutions on the kinetics and stability o f cutinase from Fusarium solani pisi were studied. The surfactant sodium bi s[2-ethylhexyl]ester sulfosuccinic acid (AOT) acts as a pseudo-competitive inhibitor within a limited concentration range relative to the hydrolysis o f short-chain p-nitrophenyl esters. For higher concentrations a hyperbolic mixed inhibition takes place. A pseudo-activation of hydrolysis in presence of AOT and hexadecyltrimethyl-ammonium bromide (CTAB) was observed. CTAB h as similar effects on kinetics of cutinase. Cutinase revealed to be stable in CTAB solutions. with activity retention as high as 80%. AOT has a delete rious effect on the enzyme in the time course, resulting in acute loss of a ctivity possibly related with unfolding of the protein structure. A relatio n between deactivation rate constants and AOT/cutinase concentration ratios is suggested. The presence of the linear alcohol, 1-hexanol, was included in these solutions, in the attempt to interpret the deactivation of cutinas e when encapsulated in reversed micelle systems in the absence of this co-s urfactant. (C) 2000 Elsevier Science B.V. All rights reserved.