Purification and characterization of the rotenone-insensitive NADH dehydrogenase of mitochondria from Arum maculatum

The non-ionic detergent lauryl dimethylamine N-oxide (LDAO) has been used to extract the NADH dehydrogenases of Arum maculatum mitochondria. Affinity chromatography on 5'-ADP-Sepharose 4B was used to separate the rotenone-sensitive (complex I) NADH dehydrogenase from the rotenone-insensitive NADH dehydrogenase. An 18-fold purification of the rotenone-insensitive NADH dehydrogenase was achieved. The enzyme is specific for NADH with optimal activity around pH 7.2. The apparent Km for NADH is 28 microM, with dichloroindophenol as acceptor at pH 7.2. The rotenone-insensitive NADH dehydrogenase appears to be a flavoprotein and no iron-sulphur centres were detected by electron spin resonance spectroscopy.