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.

scholarly journals The effect of complete or specific partial acetimidylation on the biological properties of cytochrome c and cytochrome c-T

1984 ◽  
Vol 217 (3) ◽  
pp. 595-599 ◽  
Author(s):  
C J A Wallace
Keyword(s):  
Structural Change ◽  
Cytochrome C ◽  
Oxygen Uptake ◽  
Redox Potential ◽  
Biological Properties ◽  
Amino Groups ◽  
Cytochromes C ◽  
Restricted Region ◽  
Horse Cytochrome

The biological consequences of acetimidylation of all 19 epsilon-amino groups of horse cytochrome c are a slight decrease in both the redox potential of the protein and its ability to stimulate oxygen uptake in the cytochrome c-depleted-mitochondria assay. Examination of a number of specific partially acetimidylated analogues and acetimidylated cytochromes c of other species has shown that the changes in biological properties, which are associated with a slight structural change as monitored by n.m.r. spectroscopy [Boswell, Moore, Williams, Harris, Wallace, Bocieck & Welti (1983) Biochem. J. 213, 679-686], appear to stem from modification of residues in a restricted region of the sequence. The failure of the redox potential of Saccharomyces cerevisae cytochrome c to be affected by acetimidylation suggests that it is lysine-53, absent from that species, that is the sensitive residue.

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.

The orientation of a heme of cytochrome c oxidase in submitochondrial particles

1978 ◽  
Vol 502 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Haywood Blum ◽  
H.J. Harmon ◽  
J.S. Leigh ◽  
J.C. Salerno ◽  
Britton Chance
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Submitochondrial Particles

Inhibition of Mitochondrial Electron Transfer in Rats by Ethanethiol and Methanethiol

1979 ◽  
Vol 56 (2) ◽  
pp. 147-156 ◽  
Author(s):  
T. Vahlkamp ◽  
A. J. Meijer ◽  
J. Wilms ◽  
R. A. F. M. Chamuleau
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rat Hepatocytes ◽  
Rat Liver Mitochondria ◽  
Dimethyl Sulphide ◽  
Submitochondrial Particles ◽  
Isolated Rat Hepatocytes ◽  
The Difference ◽  
Isolated Rat

1. We have investigated the effects of ethanethiol, methanethiol and dimethyl sulphide on some metabolic processes of isolated rat hepatocytes, isolated mitochondria from liver and brain and ox-heart submitochondrial particles. 2. Ethanethiol, but not dimethyl sulphide, inhibited both gluconeogenesis and ureogenesis from various substrates in rat hepatocytes, depressed cellular ATP content and caused an increased reduction of the mitochondria. 3. Ethanethiol inhibited respiration in isolated rat-liver mitochondria with several substrates, both in the presence of ADP and phosphate or in the presence of an uncoupling agent. Ethanethiol also inhibited respiration in isolated rat-brain mitochondria. Dimethyl sulphide was much less effective in inhibiting mitochondrial respiration. 4. In ox-heart submitochondrial particles ethanethiol inhibited electron transfer between cytochrome c and oxygen. 5. Purified cytochrome c oxidase was inhibited by ethanethiol in a non-competitive manner. 6. Methanethiol inhibited cytochrome c oxidase and was an effective inhibitor of mitochondrial electron transfer, both in liver and brain. 7. The difference in inhibitory properties between ethanethiol, methanethiol and dimethyl sulphide observed in our experiments coincides with the difference in potency to elicit coma in rats. We suggest that inhibition of mitochondrial electron transfer by mercaptans may be relevant to the mechanism by which energy production in brain is depressed during hepatic coma.

scholarly journals An active cytochrome c oxidase that has no tightly bound cardiolipin

1983 ◽  
Vol 209 (3) ◽  
pp. 901-903 ◽  
Author(s):  
W F Al-Tai ◽  
M G Jones ◽  
K Rashid ◽  
M T Wilson
Keyword(s):  
Steady State ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Squalus Acanthias ◽  
Submitochondrial Particles

Bovine and dogfish (Squalus acanthias) heart submitochondrial particles and cytochrome c oxidase (EC 1.9.3.1) were prepared. Biphasic Eadie-Hofstee plots from steady-state polarographic assays were obtained for both species. Phospholipid analyses indicated that cardiolipin was absent from this active dogfish enzyme.

Effects of antibodies to intact cytochrome-c oxidase and its subunit V on the enzymatic activity

1988 ◽  
Vol 66 (11) ◽  
pp. 1218-1225 ◽  
Author(s):  
P. Nicholls ◽  
C. E. Cooper ◽  
J. A. Freedman ◽  
B. D. Leece
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Membrane System ◽  
State Change ◽  
Submitochondrial Particles ◽  
Biphasic Pattern ◽  
Competitive Kinetics ◽  
Submitochondrial Particle ◽  
Enzyme Subunits ◽  
Functional Membrane

Antibodies have been raised in rabbits against whole beef heart cytochrome-c oxidase and purified subunit V. Antioxidase recognizes nearly all the enzyme subunits but reacts very strongly with subunits II and IV. Antisubunit V is quite specific against subunit V. Inhibition of enzyme activity by antioxidase is typically biphasic in time, indicating populations of both rapidly and slowly reacting molecules. Variation of cytochrome c concentration shows partially competitive kinetics, but the antibody also affects "internal" enzymatic events, including the catalytic turnover induced by N,N,N′,N′-tetramethyl-p-phenylenediamine alone and the spin-state change in cytochrome a3 that follows reduction of cytochrome a. No spectral effects can be seen however. Antioxidase also inhibits proteoliposomal respiration with external cytochrome c, but not that with internally trapped cytochrome c. No functionally significant epitopes are detectable on the N side of the membrane in proteoliposomes, although some small effects can be seen with submitochondrial particles. Antisubunit V inhibits the isolated enzyme by at least 60%. The inhibition at high ionic strength induces a biphasic pattern with respect to cytochrome c concentration. Antisubunit V may thus slow the dissociation of cytochrome c from its complex with the enzyme. Antisubunit V has only small effects on the activities of proteoliposomal and submitochondrial particle oxidase in either orientation. On subunit V, some sites, the binding of which can give rise to inhibition, are thus not accessible to antisubunit V when the enzyme is embedded in a functional membrane system.

scholarly journals Kinetics of inhibition of purified and mitochondrial cytochrome c oxidase by psychosine (β-galactosylsphingosine)

1993 ◽  
Vol 290 (1) ◽  
pp. 139-144 ◽  
Author(s):  
C E Cooper ◽  
M Markus ◽  
S P Seetulsingh ◽  
J M Wrigglesworth
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Slow Phase ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Cytochrome ◽  
Submitochondrial Particles ◽  
Bovine Heart

1. Psychosine (beta-galactosylsphingosine) is the toxic agent in Krabbe's disease (globoid cells leukodystrophy). It inhibits purified bovine heart mitochondrial cytochrome c oxidase; there is a rapid phase of inhibition (complete within 10-15 s) and a slower phase (complete within 10-15 min). Both phases are also seen in rat liver mitochondria. IC50 is about 200 microM psychosine in the purified enzyme and less than 20 microM in mitochondria. Psychosine inhibition is due to binding to cytochrome oxidase, not cytochrome c. 2. Bovine heart submitochondrial particles show inhibition similar to rat liver mitochondria. However, although proteoliposomes containing bovine heart cytochrome oxidase show an identical fast phase, they have no noticeable slow phase of inhibition. Addition of phospholipid liposomes to submitochondrial particles relieved the majority of psychosine inhibition, consistent with the removal of those molecules binding in the slow phase. Psychosine can inhibit cytochrome oxidase molecules facing in either direction in proteoliposomes and submitochondrial particles, suggesting that it can rapidly interact with both sides of a membrane when added externally. 3. At high ionic strength, the presence of psychosine decreases the Vmax. of cytochrome oxidase with little effect on the Km for cytochrome c. This non-competitive inhibition suggests that the psychosine-enzyme complex is kinetically inactive and not labile over the time course of the assay. Psychosine does not inhibit the reduction of haem a or haem a3 by artificial electron donors, but does inhibit the reduction of haem a by cytochrome c.

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