Effect of various water-miscible solvents on enzymatic activity of fungal laccases

The effect of acetonitrile, acetone and dimethyl sulfoxide (DMSO) on the catalytic activity of laccase from P. radiata and the effect of DMSO on the catalytic activity of laccase from P. oryzae in the oxidation of 2,6-dimethoxyphenol were studied. The results obtained in the studied solvent-water mixtures were satisfactorily described using the equations equivalent to the mixed enzyme inhibition. The fitted inhibition parameters were correlated with various physical and chemical parameters characterizing the mixed systems or used solvents, such as: effective pH of the reaction mixture, log P and E-T(N) of the solvent, solubility of the substrate and thermodynamic activity of water in mixed systems. Moreover, a good correlation between the inhibitory effects and the denaturation capacity of the studied solvents was observed. (C) 2000 Elsevier Science B.V. All rights reserved.