scholarly journals Oxidative phosphorylation during glycollate metabolism in mitochondria from phototrophic Euglena gracilis

1975 ◽  
Vol 150 (3) ◽  
pp. 373-377 ◽  
Author(s):  
N Collins ◽  
R H Brown ◽  
M J Merrett
Keyword(s):  
Cytochrome C ◽  
Oxygen Uptake ◽  
Oxidative Phosphorylation ◽  
Cytochrome C Oxidase ◽  
Electron Acceptor ◽  
Euglena Gracilis ◽  
Gradient Centrifugation ◽  
Antimycin A ◽  
Isolated Mitochondria ◽  
Glycollate Dehydrogenase

Mitochondria were isolated by gradient centrifugation on linear sucrose gradients from broken cell suspensions of phototrophically grown Euglena gracilis. An antimycin A-sensitive but rotenone-insensitive glycollate-dependent oxygen uptake was demonstrated in isolated mitochondria. The partial reactions of glycollate-cytochrome c oxidoreductase and cytochrome c oxidase were demonstrated by using Euglena cytochrome c as exogenous electron acceptor/donor. Isolated mitochondria contain glycollate dehydrogenase and glyoxylate-glutamate aminotransferase and oxidize exogenous glycine. A P:O ratio of 1.7 was obtained for glycollate oxidation, consistent with glycollate electrons entering the Euglena respiratory chain at the flavoprotein level. The significance of these results is discussed in relation to photorespiration in algae.

Sulphide as an inhibitor and electron donor for the cytochrome c oxidase system

1982 ◽  
Vol 60 (6) ◽  
pp. 613-623 ◽  
Author(s):  
P. Nicholls ◽  
J.-K. Kim
Keyword(s):  
Cytochrome C ◽  
Oxygen Uptake ◽  
Cytochrome C Oxidase ◽  
Submitochondrial Particles ◽  
Inhibitory Interaction ◽  
Cytochromes C ◽  
Subsequent Step ◽  
Oxidase Enzyme ◽  
Rapid Reaction ◽  
The One

Anomalies both kinetic and equilibrium in nature are described for the inhibition of cytochrome c oxidase activity by sulphide in the isolated enzyme and in submitochondrial particles. These anomalies are related to the involvement of more than 1 mol of sulphide in the blockage of one cytochrome aa3 centre. Sulphide reduces resting cytochrome a3, a reaction that results in oxygen uptake and the loss of a sulphide molecule. Sulphide can also reduce cytochromes c and a; in the former case, a part of the one-equivalent oxidation product, presumed to be the SH∙ radical, reacts with oxygen. Such oxygen uptake is also seen under aerobic conditions when ferricyanide reacts with sulphide. Three phases are identified in the inhibitory interaction of sulphide with the cytochrome c oxidase enzyme itself: an initial rapid reaction involving sulphide oxidation, oxygen uptake, and conversion of cytochrome aa3 into the low-spin "oxyferri" form; a subsequent step in which sulphide reduces cytochrome a; and the final inhibitory step in which a third molecule of sulphide binds the a3 iron centre in the cytochrome [Formula: see text] (oxy) species to give cytochrome [Formula: see text]. The initial events parallel some of the events in the interaction of the cytochrome c – cytochrome aa3 system with monothiols; the final inhibitory event resembles that with cyanide.

Characterization of partially purified microbodies from hydrocarbon-grown cells of Cladosporium resinae

1989 ◽  
Vol 35 (5) ◽  
pp. 565-572 ◽  
Author(s):  
David B. Carson ◽  
Joseph J. Cooney
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Density Gradient ◽  
Gradient Centrifugation ◽  
Urate Oxidase ◽  
Marker Enzyme ◽  
Thin Sections ◽  
Cell Extracts ◽  
Mitochondrial Fractions ◽  
A Minor

Cells of the filamentous fungus Cladosporium resinae synthesize many more microbodies when they are grown on an n-alkane than when they are grown on glucose. Cladosporium resinae was grown on n-dodecane and spheroplasts were prepared, disrupted, and fractionated by differential and density gradient centrifugation. A fraction was isolated which was enriched in catalase, a marker enzyme for microbodies. Another fraction was isolated which was enriched in cytochrome c oxidase, a marker for mitochondria. Urate oxidase, a second marker for microbodies, was not detected in cell extracts. The microbody and mitochondrial fractions were relatively free of contamination from the endoplasmic reticulum and cytosol as indicated by the amounts of glucose-6-phosphatase and glucose-6-phosphate dehydrogenase present, respectively. Transmission electron microscopy revealed that the catalase-enriched fraction contained intact microbodies, with mitochondria as a minor contaminant. Catalase was localized in microbodies by staining with 3,3′-diaminobenzidine. Mitochrondria were present in the cytochrome c oxidase enriched fraction and took up the vital stain Janus green B. In similar preparations from cells grown on glucose, catalase was largely nonparticulate. Microbodies were not observed in thin sections prepared from density gradient fractions, but mitochondria were present in a cytochrome c oxidase enriched fraction.Key words: Cladosporium resinae, microbodies, mitochondria, catalase, cytochrome c oxidase.

scholarly journals The mechanism for the ATP-induced uncoupling of respiration in mitochondria of the yeast Saccharomyces cerevisiae

1995 ◽  
Vol 307 (3) ◽  
pp. 657-661 ◽  
Author(s):  
S Prieto ◽  
F Bouillaud ◽  
E Rial
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Oxidative Phosphorylation ◽  
Cytochrome C Oxidase ◽  
Kinetic Properties ◽  
Yeast Saccharomyces Cerevisiae ◽  
Saccharomyces Cerevisiae Mitochondria ◽  
Low Efficiency ◽  
Respiratory Chain Activity

We have recently reported that ATP induces an uncoupling pathway in Saccharomyces cerevisiae mitochondria [Prieto, Bouillaud, Ricquier and Rial (1992) Eur. J. Biochem. 208, 487-491]. The presence of this pathway would explain the reported low efficiency of oxidative phosphorylation in S. cerevisiae, and may represent one of the postulated energy-dissipating mechanisms present in these yeasts. In this paper we demonstrate that ATP exerts its action in two steps: first, at low ATP/Pi ratios, it increases the respiratory-chain activity, probably by altering the kinetic properties of cytochrome c oxidase. Second, at higher ATP/Pi ratios, an increase in membrane permeability leads to a collapse in membrane potential. The ATP effect on cytochrome c oxidase corroborates a recent report showing that ATP interacts specifically with yeast cytochrome oxidase, stimulating its activity [Taanman and Capaldi (1993) J. Biol. Chem. 268, 18754-18761].

Sulphide oxidation and oxidative phosphorylation in the mitochondria of the lugworm

1997 ◽  
Vol 200 (1) ◽  
pp. 83-92 ◽  
Author(s):  
S Vökel ◽  
M K Grieshaber
Keyword(s):  
Oxygen Consumption ◽  
Cytochrome C ◽  
Oxidative Phosphorylation ◽  
Cytochrome C Oxidase ◽  
Electron Flow ◽  
Respiratory Control ◽  
Sulphide Oxidation ◽  
Atp Production ◽  
Sulphide Concentration ◽  
Flow Through

Oxygen consumption, ATP production and cytochrome c oxidase activity of isolated mitochondria from body-wall tissue of Arenicola marina were measured as a function of sulphide concentration, and the effect of inhibitors of the respiratory complexes on these processes was determined. Concentrations of sulphide between 6 and 9 µmol l-1 induced oxygen consumption with a respiratory control ratio of 1.7. Production of ATP was stimulated by the addition of sulphide, reaching a maximal value of 67 nmol min-1 mg-1 protein at a sulphide concentration of 8 µmol l-1. Under these conditions, 1 mole of ATP was formed per mole of sulphide consumed. Higher concentrations of sulphide led to a decrease in ATP production until complete inhibition occurred at approximately 50 µmol l-1. The production of ATP with malate and succinate was stimulated by approximately 15 % in the presence of 4 µmol l-1 sulphide, but decreased at sulphide concentrations higher than 15­20 µmol l-1. Cytochrome c oxidase was also inhibited by sulphide, showing half-maximal inhibition at 1.5 µmol l-1 sulphide. Sulphide-induced ATP production was inhibited by antimycin, cyanide and oligomycin but not by rotenone or salicylhydroxamic acid. The present data indicate that sulphide oxidation is coupled to oxidative phosphorylation solely by electron flow through cytochrome c oxidase, whereas the alternative oxidase does not serve as a coupling site. At sulphide concentrations higher than 20 µmol l-1, oxidation of sulphide serves mainly as a detoxification process rather than as a source of energy.

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