The markers of pig heart mitochondrial sub-fractions : I. - The dual location of NADPH-cytochrome c reductase in outer membrane and microsomes

Biochimie. 1978;60(11-12):1289-98.


Evidence is presented about the dual location of NADPH-cytochrome c reductase in mitochondrial outer membranes as well as in microsomes, from pig heart. A high specific activity, was found in both fractions, even after their purification by washing, digitonin treatments, or passages on sucrose gradients. A large fraction of the total activity was associated with both mitochondria and microsomes. Mitochondrial outer membrane differs from microsomes by a low choline phosphotransferase activity and the absence of cytochrome P-450. The properties of mitochondrial and microsomal rotenone-insensitive NADH- and NADPH-cytochrome c reductases were studied. In microsomes, both activities have the same optimum pH (8.5) ; in contrast, in mitochondria they have a different one. The Km-NADPH were always much higher than those for NADH. In mitochondria the Km for NAD(P)H were dependent on cytochrome c concentration. The results show that the rotenone-insensitive NADH- and NADPH-cytochrome c reductases of mitochondria and microsomes have quite different behavior and do not appear to be supported by the same enzyme.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Cell Fractionation
  • Cytochrome P-450 Enzyme System / analysis
  • Cytochrome Reductases / metabolism*
  • Diacylglycerol Cholinephosphotransferase / metabolism
  • Intracellular Membranes / enzymology*
  • Kinetics
  • Microsomes / enzymology*
  • Mitochondria, Heart / enzymology*
  • Myocardium / ultrastructure
  • NAD
  • NADPH-Ferrihemoprotein Reductase / metabolism*
  • Swine


  • NAD
  • Cytochrome P-450 Enzyme System
  • Cytochrome Reductases
  • NADPH-Ferrihemoprotein Reductase
  • Diacylglycerol Cholinephosphotransferase