Hydrogen peroxide, ascorbate peroxidase inhibition

Chance, (1952a) showed that hydroquinone is actually inhibitory to the Mn++-stimulated peroxidase reaction. He attributed this to competition between DHF and hydroquinone for the peroxidase peroxide compounds. It is now clear that his result was fortuitous, as it depended upon the choice of competing hydrogen donor. Even in the peroxidatic reaction, stimulation as well as competitive inhibition may occur. Thus Chance (1949b), following up an observation of Huszak (1937), found that the peroxidatic oxidation of ascorbate was stimulated by phenols, the oxidation products of the latter acting as cyclic catalysts (cf. Eq. (20) below). 

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