Interfacial binding of cutinase rather than its catalytic activity determines the steady state interfacial tension during oil drop lipid hydrolysis

Hydrolysis of triglycerides by cutinase from Fusarium solani pisi causes in oil drop tensiometer experiments a decrease of the interfacial tension. A series of cutinase variants with amino acid substitutions at its molecular surface yielded different values of the steady state interfacial tension. T his tension value poorly correlated with the specific activity as such nor with the total activity (defined as the specific activity multiplied by the amount of enzyme bound) of the cutinase variants. Moreover, it appeared th at at activity levels above 15% of that of wild type cutinase the contribut ion of hydrolysis to the decrease of the tension is saturating. A clear pos itive correlation was found between the interfacial tension plateau value a nd the interfacial binding of cutinase, as determined with attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR). These res ults indicate that the interfacial steady state level is not determined by the rate of hydrolysis, but mainly by the interfacial binding of cutinase. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.