UBIQUINONE-1 INDUCES EXTERNAL DEAMINO-NADH OXIDATION IN POTATO-TUBER MITOCHONDRIAL

The addition of ubiquinone-1 (UQ-1) induced Ca2+-independent oxidation of deamino-NADH and NADH by intact potato (Solanum tuberosum L. cv Bi ntje) tuber mitochondria. The induced oxidation was coupled to the gen eration of a membrane potential. Measurements of NAD(+)-malate dehydro genase activity indicated that the permeability of the inner mitochond rial membrane to NADH and deamino-NADH was not altered by the addition of UQ-1. We conclude that UQ-1-induced external deamino-NADH oxidatio n is due to a change in specificity of the external rotenone-insensiti ve NADH dehydrogenase. The addition of UQ-1 also induced rotenone-inse nsitive oxidation of deamino-NADH by inside-out submitochondrial parti cles, but whether this was due to a change in the specificity of the i nternal rotenone-insensitive NAD(P)H dehydrogenase or to a bypass in c omplex I could not be determined.