Structural and catalytic aspects of cutinase in w/o microemulsions

Abstract

Structural and catalytic properties of cutinase were studied in bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-isooctane microemulsion systems. The effect of the water content of the microemulsions on the cutinase activity on an esterification reaction of lauric acid with pentanol showed that cutinase followed a bell-shaped profile presenting a maximum at wo = 9, with wo =[H2O]/[AOT]. Kinetic studies allowed the determination of the apparent parameters Km and Vmax. Electron paramagnetic resonance (EPR) spectroscopy studies of active site labeled cutinase in microemulsions with varying wo values showed that in all microemulsions, the mobility of the label is higher than in the aqueous solution. Furthermore, it was found that the maximum of the enzyme activity did not correspond to a reduced active site mobility. Up to wo = 9 there was an increase of both activity and active site mobility. As the water content of the system became higher, the mobility of the bound spin label further increased whereas the enzymatic activity dropped considerably.