IDENTIFICATION AND CHARACTERIZATION OF AN INDUCIBLE NAD(P)H DEHYDROGENASE FROM RED BEETROOT MITOCHONDRIA

Exogenous NADH oxidation of mitochondria isolated from red beetroots ( Beta vulgaris L.) increased dramatically upon slicing and aging the ti ssue. Anion-exchange chromatography of soluble fractions derived by so nication from fresh and aged beetroot mitochondria yielded three NADH dehydrogenase activity peaks. The third peak from aged beetroot mitoch ondria was separated into two activities by blue-affinity chromatograp hy. One of these (the unbound peak) readily oxidized dihydrolipoamide, whereas the other (the bound peak) did not. The latter was an NAD(P)H dehydrogenase with high quinone and ferricyanide reductase activity a nd was absent from fresh beet mitochondria. Further affinity chromatog raphy of the NAD(P)H dehydrogenase indicated enrichment of a 58-kD pol ypeptide on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We propose that this 58-kD protein is the inducible, external NADH de hydrogenase.