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. Author manuscript; available in PMC: 2009 Mar 1.
Published in final edited form as: Free Radic Biol Med. 2007 Sep 25;44(5):768–778. doi: 10.1016/j.freeradbiomed.2007.09.011

Figure 1. Metabolism of menadione (MQ).

Figure 1

MQ can undergo a one electron metabolism within the mitochondria catalyzed by mitochondrial ubiquinone oxidoreductase (ubQO) to form the semiquinone (SQ−) which then participates in redox cycling through its reaction with O2 to yield the superoxide anion (O2−), regenerating MQ. MQ can also undergo a two electron metabolism within the cytosol catalyzed by DT diaphorase [NAD(P)H quinone oxidoreductase (NQO1)] resulting in the formation of hydroquinone (HQ) which is detoxified as the glucuronide or sulfate conjugates.