scholarly journals The activation of non-phosphorylating electron transport by adenine nucleotides in Jerusalem-artichoke (Helianthus tuberosus) mitochondria

1975 ◽  
Vol 152 (3) ◽  
pp. 637-645 ◽  
Author(s):  
R Sotthibandhu ◽  
J M Palmer
Keyword(s):  
Cytochrome B ◽  
Redox State ◽  
Nadh Dehydrogenase ◽  
Adenine Nucleotides ◽  
Plant Mitochondria ◽  
Jerusalem Artichoke ◽  
Simultaneous Oxidation ◽  
Carbonyl Cyanide ◽  
Bongkrekic Acid ◽  
Complex Manner

In isolated plant mitochondria the oxidation of both succinate and exogenous NADH responded in the expected manner to the addition of ADP or uncoupling agents, and the uncoupled rate of respiration was often in excess of the rate obtained in the presence of ADP. However, the oxidation of NAD+-linked substrates responded in a much more complex manner to the addition of ADP or uncoupling agents such as carbonyl cyanide p-trifluoromethoxyphenylhydrazone to mitochondria oxidizing pyruvate plus malate failed to result in a reliable stimulation; this uncoupled rate could be stimulated by adding AMP or ADP in the presence of oligomycin or bongkrekic acid. Spectrophometric measurements showed that the addition of AMP or ADP resulted in the simultaneous oxidation of endogenous nicotinamide nucleotide and the reduction of cytochrome b. ADP was only effective in bringing about these changes in redox state in the presence of Mg2+ whereas AMP did not require Mg2+. It was concluded that AMP activated the flow of electrons from endogenous nicotinamide nucleotide to cytochrome b, possible at the level of the internal NADH dehydrogenase.

scholarly journals Generation of superoxide anion by the NADH dehydrogenase of bovine heart mitochondria

1980 ◽  
Vol 191 (2) ◽  
pp. 421-427 ◽  
Author(s):  
J F Turrens ◽  
A Boveris
Keyword(s):  
Cytochrome B ◽  
Nadh Dehydrogenase ◽  
Submitochondrial Particles ◽  
Bovine Heart ◽  
Biphasic Effect ◽  
Carbonyl Cyanide ◽  
Autocatalytic Process ◽  
Ph Range ◽  
Energy Dependent ◽  
O2 Production

Submitochondrial particles from bovine heart in which NADH dehydrogenase is reduced by either addition of NADH and rotenone or by reversed electron transfer generate 0.9 +/- 0.1 nmol of O2-/min per mg of protein at pH 7.4 and at 30 degrees C. When NADH is used as substrate, rotenone, antimycin and cyanide increase O2- production. In NADH- and antimycin-supplemented submitochondrial particles, rotenone has a biphasic effect: it increases O2- production at the NADH dehydrogenase and it inhibits O2- production at the ubiquinone-cytochrome b site. The generation of O2- by the rotenone, the uncoupler carbonyl cyanide rho-trifluoromethoxyphenylhydrazone and oligomycin at concentrations similar to those required to inhibit energy-dependent succinate-NAD reductase. Cyanide did not affect O2- generation at the NADH dehydrogenase, but inhibited O2- production at the ubiquinone-cytochrome b site. Production of O2- at the NADH dehydrogenase is about 50% of the O2- generation but the ubiquinone-cytochrome b area at pH 7.4. Additivity of the two mitochondrial sites of O2- generation was observed over the pH range from 7.0 to 8.8. AN O2–dependent autocatalytic process that requires NADH, submitochondrial particles and adrenaline is described.

scholarly journals Chlortetracycline and the transmembrane potential of the inner membrane of plant mitochondria

1986 ◽  
Vol 237 (3) ◽  
pp. 765-771 ◽  
Author(s):  
I M Møller ◽  
C J Kay ◽  
J M Palmer
Keyword(s):  
Membrane Potential ◽  
Transmembrane Potential ◽  
Plant Mitochondria ◽  
Jerusalem Artichoke ◽  
Fold Increase ◽  
Nadh Oxidation ◽  
Helianthus Tuberosus ◽  
Succinate Oxidation ◽  
Bivalent Cations ◽  
Carbonyl Cyanide

The oxidation of NADH or succinate by Jerusalem-artichoke (Helianthus tuberosus L.) mitochondria in the presence of chlortetracycline induced an increase in chlortetracycline fluorescence. Any treatment that prevented the formation of a transmembrane potential (as monitored by changes in safranine absorbance, A511-A533), e.g. uncoupling with carbonyl cyanide p-trifluoromethoxyphenylhydrazone, inhibition of dehydrogenase activity or electron transport, anaerobiosis or depletion of substrate, prevented the increase in chlortetracycline fluorescence or caused it to disappear. Changes in chlortetracycline fluorescence were always slower than changes in the safranine absorbance. The increase in chlortetracycline fluorescence caused by succinate oxidation had an excitation maximum at 393 nm, indicating that a Ca2+-chlortetracycline complex was involved. The increase in fluorescence was observed even in the presence of EDTA, which removes all external bivalent cations, indicating that internal Ca2+ is mobilized. Although NADH and succinate oxidations gave the same membrane potential and qualitatively had the same effect on chlortetracycline fluorescence, NADH oxidation caused a much larger (over 3-fold) increase in chlortetracycline fluorescence than did succinate oxidation. It is possible that this is connected with the Ca2+-dependence of NADH oxidation. In the presence of 2 mM external Ca2+, chlortetracycline collapsed the transmembrane potential and uncoupled succinate and duroquinone oxidation.

scholarly journals Regulation of malate oxidation in plant mitochondria. Response to rotenone and exogenous NAD+

1982 ◽  
Vol 208 (3) ◽  
pp. 703-711 ◽  
Author(s):  
J M Palmer ◽  
J P Schwitzguébel ◽  
I M Møller
Keyword(s):  
Nadh Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Plant Mitochondria ◽  
Jerusalem Artichoke ◽  
Atp Synthesis ◽  
Matrix Space ◽  
Matrix Surface ◽  
The Matrix ◽  
Nadh Dehydrogenases ◽  
Malate Oxidation

Exogenous NAD+ stimulated the rotenone-resistant oxidation of all the NAD+-linked tricarboxylic acid-cycle substrates in mitochondria from Jerusalem artichoke (Helianthus tuberosus L.) tubers. The stimulation was not removed by the addition of EGTA, which is known to inhibit the oxidation of exogenous NADH. It is therefore concluded that added NAD+ gains access to the matrix space and stimulates oxidation by the rotenone-resistant NADH dehydrogenase located on the matrix surface of the inner membrane. Added NAD+ stimulated the activity of malic enzyme and displaced the equilibrium of malate dehydrogenase; both observations are consistent with entry of NAD+ into the matrix space. Analysis of products of malate oxidation showed that rotenone-resistant oxygen uptake only occurred when the concentration of oxaloacetate was low and that of NADH was high. Thus it is proposed that the concentration of NADH regulates the activity of the two internal NADH dehydrogenases. Evidence is presented to suggest that the rotenone-resistant NADH dehydrogenase is engaged under conditions of high phosphorylation potential, which restricts electron flux through the rotenone-sensitive dehydrogenase (coupled to ATP synthesis).

The inhibition of mammalian mitochondrial NADU oxidation by chloramphenicol and its isomers and analogues

1968 ◽  
Vol 46 (9) ◽  
pp. 1003-1008 ◽  
Author(s):  
K. B. Freeman ◽  
D. Haldar
Keyword(s):  
Cytochrome B ◽  
Respiratory Chain ◽  
Rat Liver ◽  
Nadh Dehydrogenase ◽  
Coenzyme Q ◽  
Liver Mitochondria ◽  
Heart Mitochondria ◽  
Rat Liver Mitochondria ◽  
Beef Heart ◽  
Beef Heart Mitochondria

Chloramphenicol and its isomers and analogues have been found to inhibit the oxidation of NADH, but not that of succinate, by beef heart mitochondria. They must therefore inhibit the NADH dehydrogenase segment of the respiratory chain. Chloramphenicol gave 50% inhibition at a concentration of 1 mM. The methylthio analogue of chloramphenicol inhibited NADH – coenzyme Q6 reductase but not NADH–ferricyanide reductase. Spectrophotometric observations suggest that these inhibitors act between NADH and flavin in coupled rat liver mitochondria and between flavin and cytochrome b in uncoupled beef heart mitochondria.

scholarly journals Regulation of gluconeogenesis during exposure of young rats to hypoxic conditions

1971 ◽  
Vol 121 (2) ◽  
pp. 169-178 ◽  
Author(s):  
F. J. Ballard
Keyword(s):  
Steady State ◽  
Concentration Ratio ◽  
Redox State ◽  
Adenine Nucleotides ◽  
Redox Potentials ◽  
Air Content ◽  
Hypoxic Conditions ◽  
Air Atmosphere ◽  
Old Rats ◽  
The Difference

1. Two-day-old rats were exposed at constant temperature to atmospheres containing air and nitrogen with the air content varied in steps from 100 to 0%. By using this system of graded hypoxia a comparison was made between rates of gluconeogenesis from lactate, serine and aspartate in the whole animal and the concentrations of several liver metabolites. 2. Gluconeogenesis, expressed as the percentage incorporation of labelled isotope into glucose plus glycogen, proceeds linearly for 30min when the animals are incubated in a normal air atmosphere, but is completely suppressed if the atmosphere is 100% nitrogen. 3. Preincubation of animals for between 5 and 30min under an atmosphere containing 19% air results in the attainment of a new steady state with respect to gluconeogenesis and hepatic concentrations of ATP, ADP, AMP, lactate, pyruvate, β-hydroxybutyrate and acetoacetate. 4. When lactate (100μmol), aspartate (20μmol) or serine (20μmol) was injected, it was shown that the more severe the hypoxia the greater the depression of gluconeogenesis. Under conditions when gluconeogenesis was markedly inhibited there were no changes in the degree of phosphorylation of hepatic adenine nucleotides, but free [NAD+]/[NADH] ratios fell in both cytosol and mitochondrial compartments of the liver cell. 5. Measurements of total liver NAD+ and NADH showed that the concentrations of these nucleotide coenzymes changed less with anoxia, in comparison with the concentration ratio of free coenzymes. 6. Calculations showed that the difference in NAD+–NADH redox potentials between mitochondrial and cytosol compartments increased with the severity of hypoxia. 7. From the constancy of the concentrations of adenine nucleotides it is concluded that liver of hypoxic rats can conserve ATP by lowering the rate of ATP utilization for gluconeogenesis. Gluconeogenesis may be regulated in turn by the changes in mitochondrial and cytosol redox state.

scholarly journals Charge screening by cations affects the conformation of the mitochondrial inner membrane. A study of exogenous NAD(P)H oxidation in plant mitochondria

1981 ◽  
Vol 195 (3) ◽  
pp. 583-588 ◽  
Author(s):  
I M Møller ◽  
J M Palmer
Keyword(s):  
Electron Transport ◽  
Protein Complexes ◽  
Plant Mitochondria ◽  
Lateral Diffusion ◽  
Jerusalem Artichoke ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Cations caused a decrease in the apparent Km and an increase in the Vmax. for the oxidation of exogenous NADH by both Jerusalem-artichoke (Helianthus tuberosus) and Arum maculatum (cuckoo-pint) mitochondria prepared and suspended in a low-cation medium (approximately or equal to 1 mM-K+). In Arum mitochondria the addition of cations caused a much greater stimulation of the oxidation of NAD(P)H via the cytochrome oxidase pathway than via the alternative, antimycin-insensitive, pathway. This shows that cations affected a rate-limiting step in the electron-transport chain at or beyond ubiquinone, the branch-point of electron transport in plant mitochondria. The effects were only dependent on the valency of the cation (efficiency C3+ greater than C2+ greater than C+) and not on its chemical nature, which is consistent with the theory of the diffuse layer. The results are interpreted to show that the screening of fixed negative membrane changes on lipids and protein complexes causes a conformational change in the mitochondrial inner membrane, leading to a change in a rate-limiting step of NAD(P)H oxidation. More specifically, it is proposed that screening removes electrostatic restrictions on lateral diffusion and thus accelerates diffusion-limited steps in electron transport.

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