Hydroquinone, laccase-catalyzed reaction

The concentration dependence of the oxidation current at -i-lOO mV shows threshold characteristics. In the absence of lactate, addition of hydroquinone up to 1 mM does not lead to a typical current increase. Obviously the laccase converts its substrate completely to benzo-quinone, which is not detectable at this potential. Above 1.2 mM hydroquinone the current increase reflects the breakthrough of unreacted substrate. In the presence of lactate part of the benzoquinone formed in the laccase-catalyzed reaction is recycled to hydroquinone. Therefore, the threshold is found at lower hydroquinone concentrations. 

Laccase was first identified by Yoshida [113], as a proteinaceous substance that catalyzed the lacquer curing process and it was first referred to as diastase. Bertrand [114], who had identified one of the defining reactions catalyzed by the enzyme, i.e., the ability to oxidize hydroquinone, implemented the name laccase [115],... 

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