Superoxide from glucose oxidase or from nitroblue tetrazolium?

Glucose oxidase reduces nitroblue tetrazolium, or ferricytochrome c, faster anaerobically than aerobically. This result is inconsistent with the conclusion that GO2 can reduce O2 to O2- which is then responsible for the reduction of NBT and of cytochrome c. Nevertheless, the aerobic reductions are partially inhibitable by superoxide dismutase. A scheme of reactions is proposed which explains why these electron acceptors cause an O2- production which does not occur in their absence when O2 is the sole electron acceptor.