NADH oxidation by quinone electron acceptors.

The rate constants of NADH oxidation by quinones are increased with the oxidation potential increase: log kox (M-1 X s-1) = -0.25 + 12.2 E0(7) (V) for o-quinones and log kox (M-1 X s-1) = -3.06 + 13.5 E0(7) (V) for p-quinones (pH 7.0, 25 degrees C). It is assumed that the oxidation proceeds via the hydride-ion transfer. The rate constants of NADH oxidation by single-electron quinone acceptors are also increased with the oxidizer potential increase; log kox (M-1 X s-1) = -0.64 + 9.34 E0(7) (V) and correlate with the constants of NADH oxidation by quinone radicals obtained earlier (Grodkowski, J., Neta, P., Carlson, B.W. and Miller, L. (1983) J. Phys. Chem. 87, 3135-3138). Single-electron transfer is the limiting stage of the process.