Structural and catalytic properties of enzymes in reverse micelles

Structural and catalytic properties of two enzymes--alpha-chymotrypsin and horse liver alcohol dehydrogenase (LADH)--are studied in bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-isooctane reverse-micelle solutions. Circular dichroism (CD) and electron paramagnetic resonance spectroscopy (EPR) studies show little change in alpha-chymotrypsin structure upon incorporation into reverse micelles. These structural properties explain, in part, the observed activity of these two enzymes in reverse micelles. alpha-Chymotrypsin retains activity in reverse micelles and, in some cases, displays enhanced activity. A sixfold increase in the turnover number was observed in w0 = 10 reverse micelles. LADH has low activity in reverse micelles compared to that in aqueous solution. At w0 = 70, the turnover number of LADH is 18% of the aqueous value. Active-site titrations show a decrease in active enzyme concentration for both enzymes upon incorporation into reverse micelles. Little change in the structure of both LADH and alpha-chymotrypsin is observed with change of water content in the reverse-micelle system.