Lignin peroxidase catalysed oxidation of 4-methoxymandelic acid. The role of mediator structure

A large number of substances have been tested as redox mediators in the LiP-catalysed oxidation of 4-methoxymandelic acid (4-MMA) to anisaldehyde. In some cases (i.e. thioanisole), the mediation efficiency is almost equal to the maximum value displayed by the natural mediator veratryl alcohol. The mediation efficiency is a function of the redox potential of the mediator and also appears to depend on the kinetic effectiveness with which the mediator is oxidised by the enzyme. In contrast, the lifetime of the mediator radical cation seems not to play any significant role, which would support the idea that the redox mediation is actually accomplished by a complex between the mediator radical cation and the enzyme.