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)

In an in vitro study with rat liver, ammonium meta vanadate (NH4VO3) was found to inhibit microsomal ketamine N-demethylation, lipid peroxidation, and hydrogen peroxide formation; to have no effects on 4-methylaminoantipyrine N-demethylation and on glucuronyltransferase I activity, and to enhance glucuronyltransferase II. Mitochondrial succinate dehydrogenase and cytochrome c reductase were inhibited but cytochrome oxidase activity was enhanced by ammonium vanadate. Ammonium meta vanadate increased malate dehydrogenase activity but had no effect on glutamate, lactate, glycerophosphate, isocitrate, glucose-6-phosphate, and 6-phosphogluconate dehydrogenases.
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PMID:Action of ammonium meta vanadate on hepatic enzymes in vitro. 660 35

The yeast Candida mycoderma and its mutant lacking cytochrome oxidase and cytochromes b were grown in the glucose-mineral Rieder medium and liberated hydrogen peroxide. The evolution of hydrogen peroxide was found also in the resting cells of the parent strain and its mutant when they oxidized glucose, ethanol and endogenous substrates. The evolution of hydrogen peroxide was registered also during the growth of other yeast cultures, in particular, those belonging to Saccharomyces and Torulopsis.
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PMID:[Hydrogen peroxide release into the medium by growing and resting yeast cells]. 702 45

Mitochondria are an important source of reactive oxygen intermediates because they are the major consumers of molecular oxygen in cells. Respiration is associated with toxicity, which is related to the activation of oxygen to reactive intermediates. The purpose of the present study was to examine the role of reduced glutathione (GSH) in the maintenance of mitochondrial functions during oxidative stress induced through selective inhibition of the complex III segment of the electron transport chain. Hydrogen peroxide monitored by the fluorescence of dichlorofluorescein increased in a time- and dose-dependent manner on incubation of mitochondria with antimycin A (AA), an inhibitor of complex III. However, blockade of complex I or II with rotenone or thenoyltrifluoroacetone, respectively, did not result in accumulation of hydrogen peroxide. Depletion of mitochondrial GSH to 10-20% of control by preincubation with diethylmaleate (0.8 mM) or ethacrynic acid (250 microM) also increased dichlorofluorescein and malondialdehyde levels and resulted in an additional (2-3-fold) increase after AA. Similar results were obtained when mitochondrial GSH depletion was produced by treatment with buthionine L-sulfoximine before mirochondria isolation. The endogenous oxidative stress induced by AA was accompanied by a moderate loss of activity of ATPase complex (77% of control) and complex IV of respiration (75% of control), which was accentuated after depletion of mitochondrial GSH (51% and 45% of control, respectively). Similar results were observed in isolated hepatocytes in which depletion of mitochondrial GSH and AA led to peroxidation and mitochondrial dysfunction. In addition, with electrophoretic mobility shift assay of the transcription factor nuclear factor-kappa B (NF-kappa B), we detected its activation in response to AA (2-3-fold). Depletion of mitochondrial GSH in hepatocytes (20% of control) led to further enhancement of NF-kappa B activation (2-4-fold), which correlated with generation of hydrogen peroxide. Thus, our results suggest that GSH protects mitochondria against the endogenous oxidative stress produced at the ubiquinone site of the electron transport chain. Mitochondrial GSH depletion potentiates oxidant-induced loss of mitochondrial functions. Oxidant stress in mitochondria can promote extramitochondrial activation of NF-kappa B and therefore may affect nuclear gene expression.
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PMID:Role of oxidative stress generated from the mitochondrial electron transport chain and mitochondrial glutathione status in loss of mitochondrial function and activation of transcription factor nuclear factor-kappa B: studies with isolated mitochondria and rat hepatocytes. 747 12

Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two populations of conductive events, one in the 0.1-0.5 pA range, and one in the 1.0-5.0 pA range, whereas nearly all events caused by poly-L-alanine were in the 0.1-0.5 pA range at an applied voltage of +60 mV. The channel-like activity appeared to switch between conductive and nonconductive states, with most open-times in the range of 50-200 ms. We conclude that hydrophobic polyamino acids produce proton-conducting defects in lipid bilayers that may be used to model functional proton channels in biological membranes.
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PMID:Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers. 752 Feb 89

Upon reaction of cytochrome oxidase with hydrogen peroxide, the spectral changes are complete, with slightly less than 1 equiv of hydrogen peroxide per cytochrome oxidase. At pH 8 the product is a mixture of the P and F forms, while at pH 6 the product is exclusively the F form. These data are inconsistent with current interpretations of the structure of compounds P and F. Two stable radical species are detected by EPR; the relative amounts of these species are pH dependent. The MCD spectra of pure P and F are reported. It is suggested that compound F is a hydrogen peroxide adduct of cytochrome oxidase with cytochrome a3 in the low-spin state and that compound P is an oxyferryl state of cytochrome alpha 3 in support of the recent Raman data of Proshlyakov et al. [(1994) J. Biol. Chem. 269, 29385-29388]. We also suggest that copper B is in the trivalent state in compound P.
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PMID:The interaction of cytochrome oxidase with hydrogen peroxide: the relationship of compounds P and F. 757 73

Reactive oxygen species (ROS: superoxide radical, O2.-; hydrogen peroxide, H2O2; hydroxyl radical, OH.), which arise from the univalent reduction of dioxygen are formed in mitochondria. We summarize here results which indicate that ROS, and also the radical nitrogen monoxide ('nitric oxide', NO), act as physiological modulators of some mitochondrial functions, but may also damage mitochondria. Hydrogen peroxide, which originates in mitochondria predominantly from the dismutation of superoxide, causes oxidation of mitochondrial pyridine nucleotides and thereby stimulates a specific Ca2+ release from intact mitochondria. This release is prevented by cyclosporin A (CSA). Hydrogen peroxide thus contributes to the maintenance of cellular Ca2+ homeostasis. A stimulation of mitochondrial ROS production followed by an enhanced Ca2+ release and re uptake (Ca2+ 'cycling') by mitochondria causes apoptosis and necrosis, and contributes to hypoxia/reperfusion injury. These kinds of cell injury can be attenuated at the mitochondrial level by CSA. When ROS are produced in excessive amounts in mitochondria nucleic acids, proteins, and lipids are extensively modified by oxidation. Physiological (sub-micromolar) concentrations of NO potently and reversibly deenergize mitochondria at oxygen tensions that prevail in cells by transiently binding to cytochrome oxidase. This is paralleled by mitochondrial Ca2+ release and uptake. Higher NO concentrations or prolonged exposure of cells to NO causes their death. It is concluded that ROS and NO are important physiological reactants in mitochondria and become toxic only when present in excessive amounts.
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PMID:Oxidants in mitochondria: from physiology to diseases. 759 28

We have studied the structure of the CuB site in the binuclear heme-copper center of the fully oxidized form of the quinol-oxidizing cytochrome aa3-600 from Bacillus subtilis by EXAFS and ENDOR spectroscopy. This enzyme is member of the large superfamily of heme-copper respiratory oxidases, which catalyze the reduction of dioxygen to water and link it to translocation of protons across the bacterial or mitochondrial membrane. The EXAFS of the CuB site strongly suggests tetragonal coordination by two or three histidines with one or two O/N donor ligands. There are some indications that a Cl- ion might fractionally occupy substitution-labile sites, although the majority of enzyme molecules did not contain any heavy (second row) scatters, indicative of a Cl- (or S) bridge between the heme iron and CuB [cf. Powers, L., et al. (1994) Biochim. Biophys. Acta 1183, 504-512]. Proton ENDOR spectroscopy of the CuB site in 1H2O and 2H2O media showed evidence of an oxygenous copper ligand with an exchangeable proton. 14N ENDOR revealed three inequivalent nitrogenous ligands with hyperfine coupling constants consistent with histidines. Together, these results strongly suggest that the fully oxidized enzyme has a low-symmetry, tetragonal CuB site with three histidine nitrogens and one oxygen as ligands, the latter with an exchangeable proton(s). The identity and assignment of these ligands are discussed.
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PMID:Structure of CuB in the binuclear heme-copper center of the cytochrome aa3-type quinol oxidase from Bacillus subtilis: an ENDOR and EXAFS study. 764 Feb 80

When the mixed valence, carbon monoxide-bound form of the hydroquinone-oxidizing cytochrome aa3-600 of Bacillus subtilis is illuminated in the presence of O2, it forms a species that corresponds to 'Compound C', first described for the mitochondrial cytochrome c oxidase by Chance, Saronio and Leigh (J. Biol. Chem. 250 (1975) 9226-9237). Resonance Raman spectra of the this species show a mode at 366 cm-1 that shifts to 342 cm-1 when the experiment is repeated with 18O2. The appearance of this mode is insensitive to deuteration exchange within the limits of resolution. High- (1200-1700 cm-1) and low-frequency (200-500 cm-1) data, allow us to assign the 366 cm-1 mode to the Fe(3+)-O stretching vibration of a peroxide adduct where the iron is either low or intermediate spin. This is to our knowledge the first time an 18O2-sensitive iron-oxygen stretching mode has been reported for 'Compound C', providing strong support for the notion that this species is a peroxide adduct. The observed 366 cm-1 v(Fe(3+)-O(-)-O-) frequency is 8 cm-1 higher than that previously found for a transient peroxy intermediate in the reaction between the fully reduced mitochondrial enzyme and O2. Our observation indicates that, while similar, the metastable peroxyheme a3 species reported here differs in the fine details of geometry, protonation state, and/or hydrogen bond status.
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PMID:Raman detection of a peroxy intermediate in the hydroquinone-oxidizing cytochrome aa3 of Bacillus subtilis. 764 Feb 89

In this study we have examined (1) the integrated function of the mitochondrial respiratory chain by polarographic measurements and (2) the activities of the respiratory chain complexes I, II-III, and IV as well as the ATP synthase (complex V) in free mitochondria and synaptosomes isolated from gerbil brain, after a 30-min period of graded cerebral ischaemia. These data have been correlated with cerebral blood flow (CBF) values as measured by the hydrogen clearance technique. Integrated functioning of the mitochondrial respiratory chain, using both NAD-linked and FAD-linked substrates, was initially affected at CBF values of approximately 35 ml 100 g-1 min-1, and declined further as the CBF was reduced. The individual mitochondrial respiratory chain complexes, however, showed differences in sensitivity to graded cerebral ischaemia. Complex I activities decreased sharply at blood flows below approximately 30 ml 100 g-1 min-1 (mitochondria and synaptosomes) and complex II-III activities decreased at blood flows below 20 ml 100 g-1 min-1 (mitochondria) and 35-30 ml 100 g-1 min-1 (synaptosomes). Activities declined further as CBF was reduced below these levels. Complex V activity was significantly affected only when the blood flow was reduced below 15-10 ml 100 g-1 min-1 (mitochondria and synaptosomes). In contrast, complex IV activity was unaffected by graded cerebral ischaemia, even at very low CBF levels.
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PMID:Changes of respiratory chain activity in mitochondrial and synaptosomal fractions isolated from the gerbil brain after graded ischaemia. 772 7

Electron transport and production of O2-/H2O2 by the NADH dehydrogenase flavin-semiquinone (FMNH.) and ubisemiquinone (UQH.) were studied in a model of in vivo ischemia-reperfusion in rat kidney. H2O2 production rates were assessed in isolated mitochondria using either succinate, with and without antimycin, or malate-glutamate, with and without rotenone. Respiratory activities of isolated mitochondria and activity of NADH- and succinate-cytochrome c reductase and of NADH- and succinate-dehydrogenase in submitochondrial particles were measured to evaluate the electron flux throughout respiratory carriers. The mitochondrial H2O2 production rate was approximately 1.5- and 4-times increased in ischemic and ischemic-reperfused kidneys, respectively. Ischemia caused a marked decrease in the electron transport throughout the NADH-UQ segment with no significant changes either in the NADH dehydrogenase activity or in the electron flux trough the succinate-cytochrome oxidase segment. Reperfusion did not further affect the NADH-ubiquinone segment but markedly inhibited the succinate-supported oxygen consumption, succinate-cytochrome c reductase and succinate dehydrogenase activity. Our results show a redistribution of the electron flux with an increased rate of superoxide anion/hydrogen peroxide production at NADH dehydrogenase in mitochondria subjected to ischemia only. After 10 min reperfusion an impairment of the electron flow at succinate-cytochrome c segment is established and hydrogen peroxide production by UQH. increases up to maximal values becoming the major source of superoxide anion/hydrogen peroxide.
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PMID:Mitochondrial sites of hydrogen peroxide production in reperfused rat kidney cortex. 772 10


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