Studies on the Respiratory Chain-linked Reduced Nicotinamide Adenine Dinucleotide Dehydrogenase

The reduced nicotinamide dinucleotide dehydrogenase of the respiratory chain has been further purified by gradient centrifugations at pH 10. The best preparations obtained are approximately 70% pure by sedimentation analysis and show a single flavoprotein component. The molecular weight is estimated to be of the order of 550,000, and the turnover number 800,000 per minute at 30 degrees. Provisional data are given for the NADH dehydrogenase content of heart mitochondria, Keilin-Hartree preparations, and electron transport particles. It is shown that NADH dehydrogenase contributes to the acid-extractable flavin of these preparations only to a very minor extent. (Author)