Kinetic Studies on of Veratryl the Lignin Peroxidase Catalyzed Oxidation Alcohol by H2O2 in AOT/Isooctane/ Toluene/Water Reverse Micelles

The steady state kinetics of the lignin peroxidase (LiP) catalyzed oxidation of veratryl alcohol (VA) by H₂O₂ in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/toluene/water reverse micellar medium was studied and a comparison with the corresponding aqueous medium was made to understand the effect of the reverse micellar medium on the catalytic mechanism and kinetic parameters. Results indicated that the model reaction in the AOT reverse micelle followed the ping-pong mechanism with true k_cat, K_m,VA and K being 59.6 min⁻¹, 13.9 mmol· L⁻¹ and 94.8 µmol·L⁻¹, respectively; inhibition of high level of H₂O₂ on LiP followed the reversible competitive pattern with K_i being 0.140 mmol·L⁻¹. The reaction mechanism and inhibition pattern in the AOT reverse micellar medium were the same as those in bulk aqueous medium, but the kinetic parameters except K were greatly different in the two media. The k_cat and K_i values in the reverse micelle were approximately 2 and 20 times smaller than the corresponding values in the aqueous solution, but the Michaelis constant of VA was approximately 100 times greater than that in the aqueous solution. The above mentioned differences in the kinetic parameters were caused by the microheterogeneity and the interface of the AOT reverse micelle, which resulted in the partitioning of VA and H₂O₂, and by the changes of the conformation of LiP and the reactivity of the substrates.