KINETIC-ANALYSIS OF LIGNIN PEROXIDASE - EXPLANATION FOR THE MEDIATIONPHENOMENON BY VERATRYL ALCOHOL

We investigated the role of veratryl alcohol in lignin peroxidase-cata lyzed oxidation of anisyl alcohol with pre-steady-state and steady-sta te kinetic methods. Veratryl alcohol has been proposed to act as a red ox mediator for substrates that are not directly oxidized by the enzym e. Alternatively, its mediation activity has also been attributed to i ts ability to protect the enzyme from H2O2-dependent inactivation. As previously reported, veratryl alcohol was able to stimulate the oxidat ion of anisyl alcohol. However, this stimulation is not due to mediati on or protection of the enzyme. The stimulation can be attributed to t he relative reactivity of anisyl alcohol with compounds I and II of li gnin peroxidase. We found that anisyl alcohol reacts with compound I, but not with compound II. Therefore, inclusion of veratryl alcohol or another substrate, which reacts with compound II, is essential for com pletion of the catalytic cycle.