Mechanism for the Decoloration of Orange II Catalyzed by Horseradish Peroxidase

Abstract

Study was made to clarify the mechanism for decoloration of Orange II in the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Thiol (RSH) was found to decrease the decoloration rate of Orange II. The time which takes for the decoloration rate of Orange II to start rising is equal to the time it takes for RSH to decrease and disappear. Decoloration reaction of Orange II thus occurs through formation of Orange II radicals. Next, the reaction time of HRP system was measured by the determination of the change on HRP oxidation states. Though the decoloration time of Orange II with HRP was a few seconds, the reaction time of HRP-H2O2 system was 60min. 1, 2-Naphthoquinone was separated from reaction compounds by HPLC. Therefore, it is evident that Orange II acts on HRP intermediates as a hydrogendonor to produce Orange II radicals in HRP-H2O2 reaction system and also that the reaction products of Orange II acts on HRP intermediates as a hydrogen donors.