title: The markers of pig heart mitochondrial sub-fractions : I. - The dual location of NADPH-cytochrome c reductase in outer membrane and microsomes.
abstract: 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.
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D003579:Cytochrome Reductases / Q000378:metabolism*; D002798:Diacylglycerol Cholinephosphotransferase / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D008929:Mitochondria, Heart / Q000201:enzymology*; D009206:Myocardium / Q000648:ultrastructure; D009243:NAD; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D013552:Swine
chemical_list: D009243:NAD; D003577:Cytochrome P-450 Enzyme System; D003579:Cytochrome Reductases; D009251:NADPH-Ferrihemoprotein Reductase; D002798:Diacylglycerol Cholinephosphotransferase