Titration study of guaiacol oxidation by horseradish peroxidase.
Titration of guaiacol by hydrogen peroxide in the presence of a catalytic amount of horseradish peroxidase shows that the reduction of hydrogen peroxide proceeds by the abstraction of two electrons from a guaiacol molecule. In the same way, it can be demonstrated that 0.5 mol of guaiacol can reduce, at low temperature, 1 mol of peroxidase compound I to compound II. Moreover, the reaction between equal amounts of compound I and guaiacol at low temperature produces the native enzyme. A reaction scheme is proposed which postulates that two electrons are transferred from guaiacol to compound I giving ferriperoxidase and oxidized guaiacol with the intermediary formation of compound II. The direct two-electron transfer from guaiacol to compound I without a dismutation of product free radicals must be considered as an exception to the general mechanism involving a single-electron transfer.
D004579:Electron Transport; D006139:Guaiacol; D006861:Hydrogen Peroxide; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010544:Peroxidases; D010944:Plants; D013053:Spectrophotometry; D013057:Spectrum Analysis; D013696:Temperature
D006139:Guaiacol; D006861:Hydrogen Peroxide; D010544:Peroxidases