The mechanism of ascorbic acid and hydroquinone cooxidation catalyzed by horseradish peroxidase

A steady-state kinetics of peroxidase cooxidation of ascorbic acid and hydr oquinone catalyzed by horseradish peroxidase was studied. Ascorbic acid and hydroquinone were shown to be oxidized successively, and hydroquinone prom oted the oxidation of ascorbic acid. Excess ascorbic acid inhibited peroxid ase in the cooxidation of the substrates at pH 5-7. The values of catalytic constants (k(cat), K-m, and K-a) were determined. A possible activation me chanism of the peroxidation of ascorbic acid in the presence of hydroquinon e was suggested, and its biological significance was considered.