The apparent inhibition of superoxide dismutase activity by quinones.

It has been demonstrated that several quinones can modify the activity of bovine copper superoxide dismutase by undergoing equilibrium reactions with superoxide radicals. The extent of this apparent inhibition correlates with the one electron reduction potentials of the quinones and the equilibrium constants of the semiquinone radical/superoxide radical reactions. Various rate constants have been estimated including those for the reactions of semiquinone radicals with cytochrome c and with superoxide dismutase. Semiquinone radicals cannot be dismutated by superoxide dismutase.