Activity and kinetics studies of yeast alcohol dehydrogenase in a reverse micelle formulated from functional surfactants

Yeast alcohol dehydrogenase (YADH) showed substantial decrease in its catalytic activity due to the strong electrostatic interaction between the head groups of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and YADH in AOT reverse micelles. However, the catalytic activity of YADH in a nonionic reverse micellar interface (GGDE/TX-100) obtained from a functional nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) and Triton X-100 (TX-100) was higher than that in AOT reverse micelle under the respective optimum conditions. A comparison of the kinetic parameters showed that the turnover number kcat in GGDE/TX-100 reverse micelle was 1.4 times as large as that in AOT reverse micelle, but the Michaelis constants in AOT reverse micelle for ethanol K mB was twice and for coenzyme NAD+ K mA was 5 times higher than their counterparts in GGDE/TX-100 reverse micelle. For the conversion of ethanol, the smaller K mB and larger kcat in GGDE/TX-100 reverse micelle resulted in higher catalytic efficiency kcat/K mB. The stability of YADH in GGDE/TX-100 reverse micelle was also found to be better than that in AOT reverse micelle. They were mainly attributed to the absence of electric charge on the head groups of GGDE and TX-100 in the GGDE/TX-100 reverse micelle.