Beschreibung:
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The present study compares the exogenous NAD(P)H oxidation and the membrane potential (Δψ) generated in mitochondria isolated from different tissues of an important agricultural crop, sugar beet (Beta vulgaris). We observed that mitochondria from taproots, cold-stored taproots, and in vitro-grown tissue cultures contain a functional NADH dehydrogenase, whereas only those isolated from tissue cultures displayed a functional NAD(P)H dehydrogenase. It is interesting that the NADH-dependent Δψ of mitochondria from cold-stored taproots and from tissue cultures was not affected by free Ca<sup>2+</sup> ions, whereas free Ca<sup>2+</sup> was required for the mitochondrial NADPH oxidation by in vitro-grown cells and cytosolic NADH oxidation by mitochondria from fresh taproots. A tentative model accounting for the different response to Ca<sup>2+</sup> ions of the NADH dehydrogenase in mitochondria from cold-stored taproots and tissue cultures of B. vulgaris is discussed.
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