On the presence of a nicotinamide nucleotide transhydrogenase in mitochondria from potato tuber

• Mitochondria isolated from potato (Solanum tuberosum L.) tuber wereinvestigated for the presence of a nicotinamide nucleotide transhydrogenaseactivity. Submitochondrial particles derived from these mitochondriaby sonication catalyzed a reduction of NAD' or 3-acetylpyridine-NAD'by NADPH, which showed a maximum of about 50 to 150 nanomoles/minute. milligram protein at pH 5 to 6. The Km values for 3-acetylpyridine-NAD' and NADPH were about 24 and 55 micromolar, respectively.Intact mitochondria showed a negligible activity in the absence of detergents.However, in the presence of detergents the specific activity approachedabout 30% of that seen with submitochondrial particles. Thepotato mitochondria transhydrogenase activity was sensitive to trypsinand phenylarsine oxide, both agents that are known to inhibit the mammaliantranshydrogenase. Antibodies raised against rat liver transhydrogenasecrossreacted with two peptides in potato tuber mitochondrialmembranes with a molecular mass of 100 to 115 kilodaltons. Theobserved transhydrogenase activities may be due to an unspecific activityof dehydrogenases and/or to a genuine transhydrogenase. The activitycontributions by NADH dehydrogenases and transhydrogenase to thetotal transhydrogenase activity were investigated by determining theirrelative sensitivities to trypsin. It is concluded that, at high or neutralpH, the observed transhydrogenase activity in potato tuber submitochondrialparticles is due to the presence of a genuine and specific highmolecular weight transhydrogenase. At low pH an unspecific reaction ofan NADH dehydrogenase with NADPH contributes to the total transhydrogenaseactivity. 

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Biochemistry

Biokemi

Biochemistry

Biokemi

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