2-Anilino-1.3.4-thiadiazole, Hemmstoffe der oxidativen und photosynthetischen Phosphorylierung

1975 ◽  
Vol 30 (3-4) ◽  
pp. 183-189 ◽  
Author(s):  
G. Schäfer ◽  
A. Trebst ◽  
K. H. Büchel
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxidative Phosphorylation ◽  
Benzene Ring ◽  
Inhibitory Action ◽  
Substituent Effects ◽  
Photosynthetic Electron Transport ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Oxidative Phosphorylation

Abstract 2-anilino-1,3,4-thiadiazoles carrying various substituents in the 5-position as well as in the benzene-ring were synthesized. The compounds were tested with rat-liver-mitochondria and with spinach-chloroplasts and revealed to be potent uncouplers of both, oxidative and photosynthetic phosphorylation, with p I50-values rangeing from 6.79 to 4.05. At higher concentration all compounds are inhibitors of the Hillreaction. In mitochondria a fair correlation exists between pKa of the acidic NH-group and the uncoupling activity; a maximum is obtained around pKa= 6 .8 , whereas in chloroplasts activity is shifted to more acid pKa-values. The compounds meet the requirements for uncouplers according to the chemi-osmotic theory, being lipophilic weak acids. N-methylation causes total loss of activity in mitochondrial oxidative phosphorylation. The inhibitory action on photosynthetic electron transport is located within photosystem II. This latter activity is almost independent of substituent effects in contrast to uncoupling of either respiratory- or photo-phosphorylation

scholarly journals Studies of energy-linked reactions. Inhibition of oxidative phosphorylation by DL-8-methyldihydrolipoate

1977 ◽  
Vol 164 (3) ◽  
pp. 699-704 ◽  
Author(s):  
D E Griffiths ◽  
K Cain ◽  
R L Hyams
Keyword(s):  
Oxidative Phosphorylation ◽  
Lipoic Acid ◽  
Adenosine Triphosphatase ◽  
Potent Inhibitor ◽  
Liver Mitochondria ◽  
Reduced Form ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Submitochondrial Particles ◽  
Membrane Bound

1. DL-8-Methyldihydrolipoate was shown to be a potent inhibitor of mitochondrial oxidative phosphorylation and ATP-driven energy-linked reactions. 2. ADP-stimulated respiration utilizing pyruvate + malate and succinate in both ox heart and rat liver mitochondria is inhibited; oxidative phosphorylation using pyruvate + malate, succinate and ascorbate + NNN'N'-tetramethyl-p-phenylenediamine as substrates is also inhibited; uncoupler-stimulated respiration is unaffected regardless of the substrate used. 3. Mitochondrial oligomycin-sensitive adenosine triphosphatase is inhibited in both the membrane-bound form and the purified detergent-dispersed preparation. 4. ATP-driven transhydrogenase and the ATP-driven energy-linked reduction of NAD+ by succinate in ox heart submitochondrial particles are inhibited, whereas the respiratory-chain-driven transhydrogenase is unaffected. 5. DL-8-Methyl-lipoate has no immediate effect on the above reactions, demonstrating the requirement for the reduced form for inhibition. 6. The inhibitory properties of DL-8-methyldihydrolipoate are analogous to those of oligomycin and provide further evidence of a role for lipoic acid in oxidative phosphorylation.

scholarly journals Synthesis and Antimycobacterial and Photosynthesis-Inhibiting Evaluation of 2-[(E)-2-Substituted-ethenyl]-1,3-benzoxazoles

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Ales Imramovsky ◽  
Jan Kozic ◽  
Matus Pesko ◽  
Jirina Stolarikova ◽  
Jarmila Vinsova ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Inhibitory Action ◽  
Spinacia Oleracea ◽  
Photosynthetic Electron Transport ◽  
Inhibiting Activity ◽  
Donor Side ◽  
Structure Activity Relationships ◽  
Structure Activity

A series of twelve 2-[(E)-2-substituted-ethenyl]-1,3-benzoxazoles was designed. All the synthesized compounds were tested against three mycobacterial strains. The compounds were also evaluated for their ability to inhibit photosynthetic electron transport (PET) in spinach (Spinacia oleraceaL.) chloroplasts. 2-[(E)-2-(4-Methoxyphenyl)ethenyl]-1,3-benzoxazole, 2-[(E)-2-(2,3-dihydro-1-benzofuran-5-yl)ethenyl]-1,3-benzoxazole and 2-{(E)-2-[4-(methylsulfanyl)phenyl]ethenyl}-1,3-benzoxazole showed the highest activity againstM. tuberculosis,M. kansasii,andM. avium, and they demonstrated significantly higher activity againstM. aviumandM. kansasiithan isoniazid. The PET-inhibiting activity of the most activeortho-substituted compound 2-[(E)-2-(2-methoxyphenyl)ethenyl]-1,3-benzoxazole was IC50= 76.3 μmol/L, while the PET-inhibiting activity ofpara-substituted compounds was significantly lower. The site of inhibitory action of tested compounds is situated on the donor side of photosystem II. The structure-activity relationships are discussed.

scholarly journals Oxygen, pH, and mitochondrial oxidative phosphorylation

2012 ◽  
Vol 113 (12) ◽  
pp. 1838-1845 ◽  
Author(s):  
David F. Wilson ◽  
David K. Harrison ◽  
Sergei A. Vinogradov
Keyword(s):  
Cytochrome C ◽  
Oxidative Phosphorylation ◽  
Respiratory Rate ◽  
Oxygen Sensor ◽  
Mitochondrial Respiratory Chain ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Intact Cells ◽  
Cellular Environment

The oxygen dependence of mitochondrial oxidative phosphorylation was measured in suspensions of isolated rat liver mitochondria using recently developed methods for measuring oxygen and cytochrome c reduction. Cytochrome- c oxidase (energy conservation site 3) activity of the mitochondrial respiratory chain was measured using an artificial electron donor ( N, N, N′, N′-tetramethyl- p-phenylenediamine) and ascorbate to directly reduce the cytochrome c, bypassing sites 1 and 2. For mitochondrial suspensions with added ATP, metabolic conditions approximating those in intact cells and decreasing oxygen pressure both increased reduction of cytochrome c and decreased respiratory rate. The kinetic parameters [ KM and maximal rate ( VM)] for oxygen were determined from the respiratory rates calculated for 100% reduction of cytochrome c. At 22°C, the KM for oxygen is near 3 Torr (5 μM), 12 Torr (22 μM), and 18 Torr (32 μM) at pH 6.9, 7.4, and 7.9, respectively, and VM corresponds to a turnover number for cytochrome c at 100% reduction of near 80/s and is independent of pH. Uncoupling oxidative phosphorylation increased the respiratory rate at saturating oxygen pressures by twofold and decreased the KM for oxygen to <2 Torr at all tested pH values. Mitochondrial oxidative phosphorylation is an important oxygen sensor for regulation of metabolism, nutrient delivery to tissues, and cardiopulmonary function. The decrease in KM for oxygen with acidification of the cellular environment impacts many tissue functions and may give transformed cells a significant survival advantage over normal cells at low-pH, oxygen-limited environment in growing tumors.

THE EFFECT OF RIBOFLAVIN DEFICIENCY AND GALACTOFLAVIN FEEDING ON OXIDATIVE PHOSPHORYLATION AND RELATED REACTIONS IN RAT LIVER MITOCHONDRIA

1961 ◽  
Vol 39 (1) ◽  
pp. 73-88 ◽  
Author(s):  
Robert E. Beyer ◽  
Stanley L. Lamberg ◽  
M. Arthur Neyman
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Energy Conservation ◽  
Atpase Activity ◽  
Exchange Rates ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Riboflavin Deficiency

The effect of riboflavin deficiency and feeding of galactoflavin on the flavin content of liver mitochondria, oxidative phosphorylation, Pi–ATP exchange, and ATPase activity was studied. Both dietary riboflavin deprivation and galactoflavin feeding resulted in a depressed flavin content of mitochondria, the latter treatment resulting in a more severe flavin loss. P/O ratios under all treatments were normal as were Pi–ATP exchange rates and the oxidation of succinate. Glutamate and β-hydroxybutyrate oxidations were depressed in mitochondria from rats fed galactoflavin for 15 or 28 days. DNP-activated ATPase was elevated in both flavin-deficient and galactoflavin-fed preparations while Mg++-activated ATPase was depressed in the galactoflavin-fed preparations. These results are discussed in relation to the hypothesis that flavin is involved in energy conservation in the diaphorase region of electron transport.

Inhibition of Electron Transport on the Oxygen-Evolving Side of Photosystem II by an Antiserum to a Polypeptide Isolated from the Thylakoid Membrane

1976 ◽  
Vol 31 (5-6) ◽  
pp. 304-311 ◽  
Author(s):  
Georg Schmid ◽  
Wilhelm Menke ◽  
Friederike Koenig ◽  
Alfons Radunz
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Water Splitting ◽  
Thylakoid Membrane ◽  
Inhibitory Action ◽  
Apparent Molecular Weight ◽  
Photosynthetic Electron Transport ◽  
Inhibitory Effect ◽  
Light Reaction ◽  
Tetramethyl Benzidine

Abstract A polypeptide fraction with the apparent molecular weight 11000 was isolated from stroma-freed chloroplasts from Anthirrhinum majus. An antiserum to this polypeptide fraction inhibits photosynthetic electron transport in chloroplasts from Nicotiana tabacum. The relative degree of inhibition is pH dependent and has its maximum at pH 7.4. The maximal inhibition observed was 93%. The dependence of the inhibition on the amount of antiserum yields a sigmoidal curve which hints at a cooperative effect. A calculation of the Hill interaction coefficient gave the value of 10. The inhibition occurs on the water splitting side of photosystem II between the sites of electron donation of tetramethyl benzidine and diphenylcarbazide. Tetramethyl benzidine donates its electrons before the site where diphenylcarbazide feeds in its electrons. Analysis of the steady state level of the variable fluorescence also indicates that the inhibition site is on the water splitting side of photosystem II. Tris-washed chloroplasts are equally inhibited by the antiserum and the inhibition is also observed in the presence of an inhibitor of photophosphorylation like dicyclo-hexyl carbodiimide and in the presence of the uncoupler carbonylcyanide m-chlorophenyl hydra-zone (CCCP) which means that the inhibitory action is directed towards the electron transport chain. Valinomycin which is supposed to affect the cation permeability of the thylakoid membrane has no influence on the inhibitory action of the antiserum. The same is valid for gramicidin. Methylamine on the other hand can induce a state in the thylakoids in which the antiserum is not effective. If the antibodies are already adsorbed prior to the methylamine addition then the high inhibitory effect by the antiserum remains unchanged upon addition of methylamine. From the experiments it follows that a component from the vicinity of photosystem II is ac­cessible to antibodies that is, the component is located in the outer surface of the thylakoid mem­ brane. It appears that the inhibitory effect is produced in the course of the light reaction.

scholarly journals Recovery of Oxidative Phosphorylation in Rat Liver Mitochondria after Whole Body Irradiation

1963 ◽  
Vol 238 (3) ◽  
pp. 1137-1140
Author(s):  
James C. Hall ◽  
Allan L. Goldstein ◽  
B.P. Sonnenblick
Keyword(s):  
Oxidative Phosphorylation ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Whole Body ◽  
Rat Liver Mitochondria

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

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