Mechanism of combined oxidation of ascorbic acid and hydroquinone in the presence of horseradish peroxidase]

A steady-state kinetics of peroxidase cooxidation of ascorbic acid and hydroquinone catalyzed by horseradish peroxidase was studied. Ascorbic acid and hydroquinone were shown to be oxidized successively, and hydroquinone promoted the oxidation of ascorbic acid. Excess ascorbic acid inhibited peroxidase in the cooxidation of the substrates at pH 5-7. The values of catalytic constants, (kcat, K(m), and Ka) were determined. A possible activation mechanism of the peroxidation of ascorbic acid in the presence of hydroquinone was suggested, and its biological significance was considered.