Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.9.3.1 (cytochrome oxidase)
8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of the rate of mitochondrial oxidative phosphorylation and arsenylation was studied at two external free Ca2+ concentrations. The rate of arsenate-stimulated respiration in absence of added ADP was not affected by external 10(-9) and 10(-6) M Ca2+ levels or carboxyatractyloside, while state 3 respiration was profoundly modified. In addition, the kinetic analysis showed that the rate of arsenylation in the presence of ADP was more efficient (Vm/Km ratio 3.5 times higher) in the catalytic process than phosphorylation. Therefore, this suggests that the activity of the ATP/ADP carrier is importantly controlled by Ca2+. The evaluation of the control in phosphorylation showed that the flux-control coefficients (Ci) exerted by the ATP/ADP carrier (ranged between 0.23 and 0.48) and the ATP synthase (0.05-0.57) were modified in a reciprocal way by Ca2+ and Pi concentrations. This suggests that these two enzymes are coupling sequentially through a common intermediate, the intramitochondrial ATP/ADP ratio. Other important steps controlling phosphorylation were the b-c1 complex (Ci = 0.30) and the cytochrome oxidase (Ci = 0.23) but they were not modified by Ca2+. It was also found that the main step controlling arsenylation was the ATP synthase (Ci = 0.74). The increment in the inorganic arsenate concentration induced a diminution in the control exerted by the ATP synthase (from 0.73 to 0.56). The results suggest that Ca2+ and Pi (or inorganic arsenate) could be regulated by ATP synthesis through an activating effect on ATP/ADP carrier and/or ATP synthase.
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PMID:Contribution of the translocator of adenine nucleotides and the ATP synthase to the control of oxidative phosphorylation and arsenylation in liver mitochondria. 286 40

Rates of ADP stimulated respiration for various substrates were determined in mitochondria isolated from the livers of female Sprague-Dawley rats following 8 weeks of treatment with daily swimming, ethanol consumption, or both. All rats were fed an American Institute of Nutrition (AIN) type liquid diet with the ethanol treated rats receiving 35% of the calories as ethanol. Chronic exposure to ethanol depressed both state 3 respiration with glutamate as a substrate and cytochrome oxidase activity. Respiratory control ratios and P:O ratios, however, were unaffected by the ethanol exposure. Exercise alone had no effect on hepatic mitochondrial function. There were also no significant alterations in oxidative function of hepatic mitochondria from rats which were endurance-trained by swimming while receiving the ethanol diet. This lack of alteration in mitochondrial function was in spite of the fact that these rats consumed an identical amount of ethanol as those which incurred mitochondrial dysfunction. These results indicate that regular exercise has the potential to attenuate the ethanol induced decline in hepatic mitochondria.
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PMID:Effects of exercise and ethanol on liver mitochondrial function. 288 Nov 81

Bovine heart submitochondrial particles in suspension were heated at a designated temperature for 3 min, then cooled for biochemical assays at 30 degrees C. By enzyme activity measurements and polarographic assay of oxygen consumption, it is shown that the thermal denaturation of the respiratory chain takes place in at least four stages and each stage is irreversible. The first stage occurs at 51.0 +/- 1.0 degrees C, with the inactivation of NADH-linked respiration, ATP-driven reverse electron transport, F0F1 catalyzed ATP/Pi exchange, NADH and succinate-driven ATP synthesis. The second stage occurs at 56.0 +/- 1.0 degrees C, with the inactivation of succinate-linked proton pumping and respiration. The third stage occurs at 59.0 +/- 1.0 degrees C, with the inactivation of electron transfer from cytochrome c to cytochrome oxidase and ATP-dependent proton pumping. The ATP hydrolysis activity of F0F1 persists to 61.0 +/- 1.0 degrees C. An additional transition, detectable by differential scanning calorimetry, occurring around 70.0 +/- 2.0 degrees C, is probably associated with thermal denaturation of cytochrome c and other stable membrane proteins. In the presence of either mitochondrial matrix fluid or 2 mM mercaptoethanol, all five stages give rise to endothermic effects, with the absorption of approx. 25 J/g protein. Under aerobic conditions, however, the first four transitions become strongly exothermic, and release a total of approx. 105 J/g protein. Solubilized and reconstituted F0F1 vesicles also exhibit different inactivation temperatures for the ATP/Pi exchange, proton pumping and ATP hydrolysis activities. The first two activities are abolished at 49.0 +/- 1.0 degrees C, but the latter at 58.0 +/- 2.0 degrees C. Differential scanning calorimetry also detects biphasic transitions of F0F1, with similar temperatures of denaturation (49.0 and 54.0 degrees C). From these and other results presented in this communication, the following is concluded. (1) A selective inactivation, by the temperature treatment, of various functions of the electron-transport chain and of the F0F1 complex can be done. (2) The ATP synthesis activity of the F0F1 complex involves either a catalytic or a regulation subunit(s) which is not essential for ATP hydrolysis and the proton translocation. This subunit is 10 degrees C less stable than the hydrolytic site. Micromolar ADP stabilizes it from thermal denaturation by 4-5 degrees C, although ADP up to millimolar concentration does not protect the hydrolytic site and the proton-translocation site.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Thermal inactivation of electron-transport functions and F0F1-ATPase activities. 288 70

This study documents the effects of an intracarotid artery injection of a lethal threshold amount of KCN (2.5 mg.kg-1) on the energy metabolism and histology of the rat brain. This dose of KCN resulted in a rapid abolition of electroencephalographic activity, which remained essentially absent for up to 3 h. Cerebral metabolite measurements 0.25 h after KCN infusion indicated a 52% reduction in cytochrome oxidase activity, a 600% increase in lactate, a 32% reduction in ATP, a 73% increase in ADP, and an 85% decrease in glycogen. Measurements of the above energy metabolites over the ensuing 7 days showed a return to control of all metabolites by 6-24 h. Corresponding to the normalization of energy metabolism was a return of EEG and conscious activity. Histological examination of cyanide-exposed animals revealed a paucity of change with only one animal at 0.5 h showing several dark neurons, two animals at 1 h with minor pallor of corpus callosum and caudate-putamen, and one animal at 48 h with a small hippocampal infarction. It is concluded that it may be impossible to produce a serious enough disruption of cerebral metabolism with KCN injection, to produce neuronal damage by purely "histotoxic" mechanisms.
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PMID:Cerebral energy metabolism in cyanide encephalopathy. 292 Dec 90

Mitoplasts were prepared from 3-h ischemic livers in an attempt to define the structural alterations in the inner membrane that may account for the functional deficiencies of ischemic mitochondria. Mitoplasts from both control and ischemic livers had similar specific activities of cytochrome oxidase and succinate-cytochrome c reductase. With both preparations, the specific activity of rotenone-insensitive NADH-cytochrome c reductase was 10-fold lower than in the mitochondria from which they were prepared. Ischemic mitoplasts had no respiratory control with ADP, and had a slightly reduced phospholipid to protein ratio and an increased cholesterol to protein ratio. As a result, the cholesterol to phospholipid molar ratio was increased from the control of 0.04 to 0.08. There were also differences in the content of individual phospholipid species. Phosphatidylcholine increased by 15%, while cardiolipin decreased by 60%. There were increases in sphingomyelin and in the lysophospholipids of phosphatidylcholine, ethanolamine, and cardiolipin. Pretreatment with chlorpromazine did not prevent these changes. Linoleic acid was decreased by 35% in ischemic phospholipids, and the content of free fatty acids was increased 4-fold. Electron spin resonance spectroscopy of mitoplasts spin labeled with either 5- or 12-doxyl stearic acid revealed an increased molecular order (decreased fluidity) of ischemic inner mitochondrial membranes consistent with the increased cholesterol to phospholipid ratio. The data indicate activation of a phospholipase A in ischemic mitochondria with the resulting accumulation of products of lipid hydrolysis. This conclusion further emphasizes the close similarity between the structural and functional consequences of ischemia in the intact animal and the effect on isolated mitochondria of the activation of the endogenous phospholipase A. In both cases the major functional alterations are attributable to changes in the permeability of the inner mitochondrial membrane induced by the accumulation of lysophospholipids.
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PMID:Structural alterations of the inner mitochondrial membrane in ischemic liver cell injury. 298 20

Proteolytic activities in bovine adrenocortical mitochondria were investigated using [14C-methyl]casein as a substrate. Washed mitochondria showed a low proteolytic activity at pH 7.5 or 8.2. ATP (5 mM) plus MgCl2 (7.5 mM) stimulated the proteolysis 9 times at pH 8.2. It was further demonstrated unequivocally by various approaches that the ATP-dependent proteolytic activity localizes in mitochondrial matrix. The activity of the solubilized protease was sensitive to N-ethylmaleimide, mersalyl acid, phenylmethylsulfonyl fluoride, o-vanadate, m-vanadate, vanadyl sulfate, and quercetin but not by oligomycin and ouabain. The ATP-dependent proteolytic activity was eluted at the position of 650,000 daltons on an Ultrogel AcA 22 column as a single symmetrical peak. The gel-filtered enzyme showed high specificity to ATP. GTP and UTP partially substituted ATP. ADP, AMP, tripolyphosphate, alpha, beta-methylene ATP, and beta, gamma-methylene ATP had little or no stimulating activity. ATP did not stimulate the activity in the absence of MgCl2. We measured ATP-dependent proteolytic activities in mitochondrial fractions from several tissues in rat and bovine. Adrenal cortex was one of the tissues of highest activity. In addition, we investigated the effect of adrenal atrophy on the ATP-dependent protease activity in rat adrenal. The ATP-dependent protease activity/adrenal decreased by dexamethasone treatment. The extent of the decrease was similar to that of cytochrome oxidase and succinate dehydrogenase, but smaller than that of cytochrome P-450.
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PMID:ATP-dependent protease in bovine adrenal cortex. Tissue specificity, subcellular localization, and partial characterization. 298 96

Oxidized dialdehyde analogs of ADP or ATP (oADP and oATP) were shown to inhibit irreversibly adenine nucleotide translocator (T) and creatine kinase (CK) in heart mitochondria. Inactivation of T and CK was parallel with carboxyatractyloside - sensitive and (ADP + phosphocreatine) - sensitive incorporation of o[3H]ADP into mitochondria, respectively. o[3H]ADP incorporation sensitive to CAT or ADP+phosphocreatine was used to determine T and CK contents in mitochondria. T content in cardiac mitochondria from rat, rabbit, dog, and chicken was calculated to be 2.6 - 2.9 moles/mole cyt.aa3. The same value of T/cyt.aa3 ratio was found in liver mitochondria with lower cytochrome aa3 content. In all types of cardiac mitochondria CK content was found to be 2.4 - 2.6 moles/mole cyt.aa3. The data show that T and CK are present in molar ratio 1:1 in all types of cardiac mitochondria.
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PMID:Affinity modification of creatine kinase and ATP-ADP translocase in heart mitochondria: determination of their molar stoichiometry. 300 38

Liver mitochondria from Cu-deficient rats exhibit impaired State 3 respiration (oxygen consumption in the presence of exogenous ADP) compared with Cu-adequate controls, whereas State 4 respiration (oxygen consumption after depletion of exogenous ADP) and ADP/O are unaffected. In view of previous observations (Davies, N.T., Lawrence, C.B., Mills, C.F. and Nicol, F. (1985) Biochim. Biophys. Acta 809, 351-361) it seemed that a decline in cytochrome c oxidase activity (EC 1.9.3.1) could not fully account for these findings. Cu deficiency resulted in a significant decline (40%, P less than 0.01) in [14C]ADP uptake by liver mitochondria which suggests there is a reduced activity of the adenine nucleotide translocase. The reduced translocase activity was not associated with any marked change in fatty-acid composition of either intact mitochondria or inner mitochondrial membranes. Inhibitor titrations with the irreversible inhibitor carboxyatractyloside showed that 'Cu-deficient' mitochondria required the same concentration of inhibitor to produce 100% inhibition of State 3 respiration as control mitochondria, suggesting that the amount of functional translocase enzyme present is unaffected. When the translocase assay was allowed to proceed until equilibrium was established between external and internal nucleotides, it was apparent that the exchangeable adenine nucleotide pool of Cu-deficient mitochondria was 36% lower than in controls. Analysis of mitochondria for their ATP, ADP and AMP contents showed that, whereas the AMP content was unaffected, ATP and ADP contents were 39 and 40% lower, respectively, which resulted in a significantly reduced pool of total adenine nucleotides (ATP + ADP + AMP) and a reduced 'energy charge' [(ATP + 0.5 ADP)/(ATP + ADP + AMP)]. These results are discussed in relation to current concepts of the regulation and control of mitochondrial respiration.
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PMID:Studies on the effect of copper deficiency on rat liver mitochondria. III. Effects on adenine nucleotide translocase. 300 76

Glucagon has been shown to increase further the enhanced tolerance for hypoxia of mice with elevated blood ketones and to stimulate ketone utilization by rat brain slices, suggesting that glucagon may affect brain metabolism. In addition to stimulating gluconeogenesis, glucagon alters the metabolism of mitochondria isolated from liver and heart. This study was designed to test whether glucagon can act directly and selectively on brain mitochondrial substrate oxidation. Mitochondria were isolated from normal murine brains using differential centrifugation through Ficoll gradients. Glucagon (3.6 microM) stimulated respiration in the presence of glutamate, and glutamate plus beta-hydroxybutyrate, but not in the presence of glutamate plus malate, succinate or beta-hydroxybutyrate alone. With glutamate as the substrate the hormone significantly increased State 3 oxygen consumption rates from control values of 91 mol O2/mol of cytochrome aa3/min to 117 mols O2/mol/aa2/min (p less than 0.0001), and also increased State 4 rates slightly but significantly. Glucagon did not change mitochondrial respiratory control ratios, but increased estimated rates of ATP synthesis from 434 (control) to 597 mols ADP consumed/mol aa3/min (p less than 0.0001). The data indicate that in vitro glucagon has a direct and substrate-specific stimulatory effect on isolated brain mitochondria. These substrate-specific effects were not altered when respiration was studied in the presence of postmitochondrial supernatant or exogenous 3',5'-cyclic AMP, indicating that glucagon, in addition to an in vivo action via activation of membrane-bound adenylate cyclase, can act, at least in vitro, directly and selectively on brain mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Substrate-specific stimulation by glucagon of isolated murine brain mitochondrial oxidative phosphorylation. 300 83

Bovine heart cytochrome-c oxidase was reconstituted in liposomes and the kinetics of cytochrome c oxidation were measured by the polarographic and photometric method under uncoupled conditions in the presence of various polyvalent anions. In order to distinguish between specific and unspecific ionic effects of ATP, the photolabelling reagent 8-azido-ATP was applied. Covalently bound ATP at the enzyme complex caused the same increase of Km for cytochrome c as free ATP, if measured by the photometric assay. The increase of Km by photolabelling with 8-azido-ATP was completely prevented by ATP, but not by ADP. The data indicate the occurrence of a specific binding site for ATP at the cytosolic side of cytochrome-c oxidase, which, after binding of ATP, changes the kinetics of cytochrome c oxidation.
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PMID:Specific effects of ATP on the kinetics of reconstituted bovine heart cytochrome-c oxidase. 302 30


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