scholarly journals Thyroidal regulation of substrate kinetics properties of cytochrome oxidase in rat liver mitochondria

2008 ◽  
Vol 23 (3) ◽  
pp. 272-278
Author(s):  
Hiren R. Modi ◽  
Surendra S. Katyare ◽  
Samir P. Patel
Keyword(s):  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Substrate Kinetics

scholarly journals Proton translocation by the mitochondrial cytochrome b-c1 complex is inhibited by NN′-dicyclohexylcarbodi-imide

1982 ◽  
Vol 206 (2) ◽  
pp. 419-421 ◽  
Author(s):  
B D Price ◽  
M D Brand
Keyword(s):  
Electron Transport ◽  
Cytochrome Oxidase ◽  
Cytochrome B ◽  
Rat Liver ◽  
Proton Translocation ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Cytochrome ◽  
Low Concentrations ◽  
Mitochondrial Cytochrome B

NN'-Dicyclohexylcarbodi-imide at low concentrations decreases the H+/2e ratio for rat liver mitochondria over the span succinate to oxygen from 5.9 +/- 0.3 (mean +/- S.E.M.) to 4.0 +/- 0.1 and for the cytochrome b-c1 complex from 3.8 +/- 0.2 to 1.9 +/- 0.1, but has little effect on the H+/2e ratio of cytochrome oxidase. The decrease in stoicheiometry is due, not to uncoupling or inhibition of electron transport, but to inhibition of proton translocation. NN'-Dicyclohexylcarbodi-imide thus ‘decouples’ proton translocation in the cytochrome b-c1 complex.

Succinic and Cytochrome Oxidase Activity of Rat Liver Mitochondria After in Vitro Irradiation With Ultraviolet Light

1957 ◽  
Vol 188 (3) ◽  
pp. 547-549 ◽  
Author(s):  
Attilio Canzanelli ◽  
Rhea Sossen ◽  
David Rapport
Keyword(s):  
Cytochrome Oxidase ◽  
Ultraviolet Light ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Biological Effects ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cytochrome Oxidase Activity ◽  
Order Of Magnitude

Five per cent suspensions of rat liver mitochondria were irradiated with ultraviolet light for varying periods of time and the succinoxidase and cytochrome oxidase activity were determined. Both succinoxidase and cytochrome oxidase activity were reduced by irradiation with ultraviolet. The order of magnitude of the ultraviolet energy necessary to produce such changes is much less than that necessary to produce chemical changes in nucleic acid derivatives, and approaches the amount which has been shown to produce lethal and other biological effects.

scholarly journals Evidence for the sequential assembly of cytochrome oxidase subunits in rat liver mitochondria

1983 ◽  
Vol 212 (3) ◽  
pp. 829-834 ◽  
Author(s):  
A Wielburski ◽  
B D Nelson
Keyword(s):  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Temporal Sequence ◽  
Temporal Association ◽  
Rat Liver Mitochondria ◽  
Assembly Process ◽  
Isolated Rat Hepatocytes ◽  
Isolated Rat

The assembly of cytochrome oxidase was studied in isolated rat liver mitochondria and isolated rat hepatocytes labelled in vitro with L-[35S]methionine. This was achieved by studying the temporal association of radioactive subunits which are immunoabsorbed with antibodies against subunits I, II and the holoenzyme. Antibodies against the holoenzyme were shown to be highly specific for subunit V. The results show that subunit I appears in the holoenzyme late in the assembly process. No radioactive subunit I is absorbed with antiserum against subunit II or the holoenzyme (subunit V) after a 30 min pulse in either isolated mitochondria or hepatocytes. However, both antisera absorb radioactive subunits I after a 150 min chase in isolated hepatocytes. This was confirmed using antibodies against subunit I, which absorbed only radioactive subunit I after a 30 min pulse but absorbed radioactive subunits I-III and VI after a 150 min chase. Thus, the late assembly of radioactive subunit I is explained by a temporal sequence in the assembly process and not by the presence of a large, non-radioactive pool of subunit I. Using the above approach and the three specific antisera, the following temporal sequence in the assembly of cytochrome oxidase was established. Subunits II and III assemble rapidly with each other or with cytoplasmically translated subunit VI. This complex of three peptides in turn assembles slowly with subunit I or with the other cytoplasmically translated subunits. The early association of subunit VI with the mitochondrially translated subunits II and III suggests a possible role of the former in integration of the holoenzyme.

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.

ENZYME INHIBITION BY DERIVATIVES OF PHENOTHIAZINE

1952 ◽  
Vol 30 (6) ◽  
pp. 443-446
Author(s):  
H. B. Collier ◽  
G. M. Allenby
Keyword(s):  
Oxygen Uptake ◽  
Cytochrome Oxidase ◽  
Enzyme Inhibition ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cytochrome Oxidase Activity ◽  
Derivatives Of

The succinoxidase activity of rat-liver mitochondria was strongly inhibited by the following compounds (concentration for 50% reduction in rate of oxygen uptake is given in brackets): phenothiazine (1.4 × 10−5 M), phenothiazine sulphoxide (2.8 × 10−5 M), and phenothiazone (5.4 × 10−5 M). Thionol was only slightly inhibitory. The cytochrome oxidase activity of mitochondria was not inhibited by any of these compounds.

scholarly journals Proton translocation by cytochrome oxidase in (antimycin + myxothiazol)-treated rat liver mitochondria using ferrocyanide or hexammineruthenium as electron donor

1986 ◽  
Vol 236 (1) ◽  
pp. 15-21 ◽  
Author(s):  
I C West ◽  
R Mitchell ◽  
A J Moody ◽  
P Mitchell
Keyword(s):  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Choline Chloride ◽  
Proton Translocation ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Second Phase ◽  
O2 Consumption ◽  
Rapid Phase

When O2 was injected into an anaerobic suspension of valinomycin-treated rat liver mitochondria inhibited with rotenone, antimycin, and myxothiazol, a small amount of O2 (0.23-0.33 ng-atom of O/mg of protein) was reduced extremely rapidly (within the 2 s time-resolution of the oxygen electrode). The subsequent steady-state rate of flow of electrons to oxygen was very low [less than 3 nequiv. X s-1 X (g of mitochondrial protein)-1]. In the presence of valinomycin there was a rapid ejection of protons synchronous with the rapid phase of O2 consumption corresponding to 0.38-0.61 nequiv. of H+ X (mg of mitochondrial protein)-1. When valinomycin was replaced by carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) there was a rapid alkalification of the medium corresponding to 0.20-0.42 nequiv. of H+ X (mg of mitochondrial protein)-1. When 2 mM-Fe(CN)6(4-) was present to re-reduce endogenous cytochrome c, O2 consumption was still biphasic but the second phase of O2 consumption was very much more rapid [600 nequiv. X s-1 X (g of protein)-1], and resulted in the virtually complete consumption of the O2 in the pulse within 4 s. With 60 microM-Ru(NH3)6(2+) as reductant, O2 consumption was even faster [1200 nequiv. X s-1 X (g of protein)-1]. In a medium containing 150 mM-choline chloride with Ru(NH3)6(2+) as reductant, the proton per reducing equivalent stoichiometry (delta H+O/e-) was +0.95 in the presence of valinomycin and −0.94 in the presence of FCCP. In choline chloride medium containing Ru(NH3)6(2+) and valinomycin, there was an uptake of K+ ions corresponding to 1.86 K+/e-. It is concluded that nearly 1 proton is translocated outwards through cytochrome oxidase per oxidizing equivalent injected in this medium. In low ionic strength sucrose-based medium, with Ru(NH3)6(2+) as reductant, delta H+O/e- was 1.05 in the presence of valinomycin, and −0.71 in the presence of FCCP. It is concluded that the translocation of protons is accompanied by net acid production in this medium.

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