Catalytic activity of enzyme in water/organic cosolvent mixtures for the hydrolysis of p-nitrophenyl acetate and p-nitrophenyl benzoate

The dependence of the catalytic activities of alpha-chymotrypsin on the concentration of organic cosolvents (acetonitrile, dimethyl sulfoxide, dimethyl formamide, ethylene glycol, methanol, ethanol, propan-2-ol and tert-butanol) in mixed aqueous media has been studied towards hydrolysis of p-nitrophenyl acetate and p-nitrophenyl benzoate using cetyltriphenylphosphonium bromide surfactant at pH 7.75. The temperature dependence hydrolysis of PNPA and PNPB catalyzed by alpha-chymotrypsin has also been reported. Under all the conditions employed, the reaction follows a Michaelis-Menten mechanism. The organic solvent influences the k(cat) and K-M. The effect of polarity of solvent on the catalytic activity has been discussed. It is observed that the catalytic efficiency of alpha-chymotrypsin is enhanced in aqueous-organic media. Possible mechanism of micellar enzymology and the effect of organic co-solvents have been discussed.