A High-Energy Phosphate Requirement for Succinate Oxidation in Uncoupled Rat Liver Mitochondria

Nature ◽  
1960 ◽  
Vol 187 (4731) ◽  
pp. 65-67 ◽  
Author(s):  
GIOVANNI FELICE AZZONE ◽  
LARS ERNSTER
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
High Energy ◽  
Rat Liver Mitochondria ◽  
High Energy Phosphate ◽  
Succinate Oxidation

THE INHIBITION OF OXIDATIVE AND PHOSPHORYLATIVE ENZYMES IN RAT LIVER MITOCHONDRIA BY AMINOAZOBENZENE DERIVATIVES

1960 ◽  
Vol 38 (1) ◽  
pp. 1-11 ◽  
Author(s):  
W. C. McMurray
Keyword(s):  
Cytochrome C ◽  
Rat Liver ◽  
Pyridine Nucleotide ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Metabolic Block ◽  
Liver Carcinogen ◽  
Mitochondrial Dehydrogenase Activity

The liver carcinogen, dimethylaminoazobenzene, inhibited in vitro the oxidation of a variety of pyridine nucleotide linked substrates of rat liver mitochondria without affecting the process of oxidative phosphorylation. Cytochrome c oxidase activity was not inhibited by the carcinogen, nor was the succinoxidase activity, but the phosphorylation accompanying succinate oxidation was uncoupled. Similar effects were noted with other aminoazobenzene derivatives, but did not appear to be correlated with the ability of the compounds to evoke tumors.The site of the respiratory inhibition by dimethylaminoazobenzene appears to be at the level between reduced pyridine nucleotide and cytochrome c in the respiratory chain. Mitochondrial dehydrogenase activity was not inhibited, while the oxidation of reduced diphosphopyridine nucleotide was markedly decreased. The reduction of the electron acceptor, ferricyanide, by pyridine nucleotide linked substrates was also strongly inhibited but the reduction of tetrazolium compounds was not affected. The latter observations suggest that dimethylaminoazobenzene produces a metabolic block between reduced flavin and cytochrome c in the mitochondrial electron transport system.

scholarly journals The inhibition of pyruvate and ls(+)-isocitrate oxidation by succinate oxidation in rat liver mitochondria

1969 ◽  
Vol 114 (3) ◽  
pp. 589-596 ◽  
Author(s):  
T. König ◽  
D. G. Nicholls ◽  
P. B. Garland
Keyword(s):  
Cytochrome B ◽  
Rat Liver ◽  
Rat Heart ◽  
Fold Increase ◽  
Liver Mitochondria ◽  
Inhibitory Effect ◽  
The Other ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Rapid Flow

1. The effects of succinate oxidation on pyruvate and also isocitrate oxidation by rat liver mitochondria were studied. 2. Succinate oxidation was without effect on pyruvate and isocitrate oxidation when respiration was maximally activated with ADP. 3. When respiration was partially inhibited by atractylate, succinate oxidation severely inhibited the oxidation of pyruvate and isocitrate. 4. This inhibitory effect of succinate was associated with a two- to three-fold increase in the reduction of mitochondrial NAD+ but no change in the reduction of cytochrome b. 5. It is concluded that, in the partially energy-controlled state, respiration is more severely inhibited at the first phosphorylating site than at the other two. 6. The effects of succinate oxidation are compared with those of palmitoylcarnitine oxidation. It is concluded that a rapid flow of electrons directly into the respiratory chain at the level of cytochrome b is in itself inadequate to inhibit the oxidation of intramitochondrial NADH. 7. The effects of succinate oxidation on pyruvate oxidation were similar in rat heart and liver mitochondria.

scholarly journals Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria

1972 ◽  
Vol 129 (2) ◽  
pp. 355-365 ◽  
Author(s):  
T. Spencer ◽  
F. L. Bygrave
Keyword(s):  
Rat Liver ◽  
Calcium Ions ◽  
Adenine Nucleotide ◽  
Cell Metabolism ◽  
Liver Mitochondria ◽  
High Energy ◽  
Small Degree ◽  
Metabolic Inhibitors ◽  
Rat Liver Mitochondria ◽  
Stimulation Of

1. Added Ca2+stimulates the translocation of ATP by isolated rat liver mitochondria. 2. The apparent Km for added Ca2+in stimulating the translocation of 200μm-ATP is approx. 160μm (75μm ‘free’ Ca2+). 3. The greatest stimulation of ATP translocation by Ca2+occurs at the lower concentrations of ATP. 4. Sr2+(and to a lesser extent Ba2+) can replace Ca2+whereas Mg2+and Mn2+have only little ability to stimulate ATP translocation. 5. Translocation of dATP is also stimulated by Ca2+whereas that of ADP is stimulated to only a relatively small degree. 6. Studies with metabolic inhibitors and uncouplers provide evidence that stimulation by Ca2+and by uncouplers is additive and that the mechanism of Ca2+stimulation does not seem to involve the high-energy intermediate of oxidative phosphorylation. 7. In the presence of Ca2+, ATP is able to effectively compete with ADP for translocation. 8. Added K+further enhances the ability of Ca2+to stimulate ATP translocation. 9. These findings are discussed in relation to the potential involvement of Ca2+in modifying enzymic reactions involved in the regulation of cell metabolism.

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