Effect of mass transfer limitation on the enzyme reaction in reversed micelle

Abstract

The theoretical and experimental studies concerning mass transfer effect on enzyme reaction in reverse micelle were carried out. Firstly, the theoretical analysis showed that in the case of Michaelis-Menten kinetics, the apparent Michaelis constant increased with increasing substrate transfer limitation, but the apparent maximum reaction rate was constant. The experimental evidence obtained for the trypsin catalyzed hydrolysis in reverse micelle by Martinek et al. [1] supports the results of our theoretical analysis. Secondly, an experimental result demonstrating that the substrate transfer across the interface was a rate limiting factor in the enzyme reaction was obtained. When the horse liver alcohol dehydrogenase activity was determined by the rate of increase in fluorescence intensity of NADH, two different slopes was observed and this could be due to the rate limitation of substrate transfer across the interface. As the carbon number of primary alcohol is increased, the ratio between two slopes(second slope over first one)which represents the degree of substrate transfer limitation increases, except for heptanol and octanol. This result could be explained by the rate limitation of substrate transfer and substrate specificity of the enzyme : As the substrate specificity of the enzyme is increased, the limitation of substrate transfer becomes more severe.