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)

We studied energy metabolism after experimental subarachnoid hemorrhage in rats. Four different cerebral areas were tested: frontal cortex, occipital cortex, hippocampus, and brainstem. Vmax of the following enzymatic activities was evaluated: in the homogenate: hexokinase, phosphofructokinase, and lactate dehydrogenase for the glycolytic pathway, and glucose-6-phosphate dehydrogenase for the hexose monophosphate shunt; in the purified nonsynaptic mitochondria: NAD+-isocitrate dehydrogenase, citrate synthase, and succinate dehydrogenase for the Krebs cycle, and cytochrome oxidase for the electron transfer chain. We also evaluated some parameters related to the respiration of nonsynaptic mitochondria (State 3, State 4, uncoupled state, respiratory control ratio, and ADP:O ratio). Subarachnoid hemorrhage did not significantly affect Vmax of the enzymatic activities related to anaerobic and aerobic metabolism; however, mitochondrial respiration was affected, particularly in the presence of NADH-producing substrates (glutamate + malate).
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PMID:Bioenergetics of different brain areas after experimental subarachnoid hemorrhage in rats. 335 25

Mitochondria from bundle sheath cells of the phosphoenolpyruvate carboxykinase-type C4 species Urochloa panicoides were shown to have metabolic properties consistent with a role in C4 photosynthesis predicted from earlier studies. The rate of O2 uptake in response to added malate plus ADP was at least five times the activity observed with NADH, glycine, or succinate. With malate plus ADP the O2 uptake rate averaged about 150 nmol O2 min-1 mg-1 protein, equivalent to about 0.6 mumol min-1 mg-1 of extracted chlorophyll. About half of this activity was apparently phosphorylation-linked with ADP/O2 ratios of about 4. Studies with electron transport inhibitors suggested that about 65% of this malate oxidation is cytochrome oxidase-terminated with a minor component mediated via the alternative oxidase. These mitochondria supported rapid rates of pyruvate production from malate and this activity was also stimulated by ADP but blocked by inhibitors of electron transport. Adding oxaloacetate increased pyruvate production but inhibited O2 uptake. The results were consistent with the notion that in this subgroup of C4 species mitochondrial-located NAD malic enzyme contributes substantially to total C4 acid decarboxylation. This enzyme is apparently also the primary source of NADH necessary to generate the ATP required for phosphoenolpyruvate carboxykinase-mediated oxaloacetate decarboxylation.
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PMID:Photosynthesis in phosphoenolpyruvate carboxykinase-type C4 plants: activity and role of mitochondria in bundle sheath cells. 335 56

O2 uptake by the perfused liver decreased at O2 concentrations considerably higher than levels that caused NADH reduction when the input O2 concentration was varied. The maximal rate of O2 uptake was two- to threefold higher in periportal (137 +/- 8 mumol . g-1 . h-1; O2 concentration = 478 +/- 37 microM) than pericentral regions (59 +/- 5 mumol . g-1 . h-1; O2 concentration = 263 +/- 21 microM); however, the O2 concentration required for half-maximal O2 uptake was similar (approximately 20 microM) in the two areas. The infusion of atractyloside, antimycin A, or KCN inhibited O2 uptake in both zones by 50-85%, indicating that O2 uptake in both regions was largely dependent on mitochondrial electron transport. The content of ATP and ADP and ATP:ADP were similar in microdissected samples from periportal and pericentral areas. In contrast, when livers were perfused in the retrograde direction, O2 uptake was two- to threefold greater in pericentral than in periportal regions. Maximal rates of O2 uptake correlated with the local O2 concentration irrespective of the direction of flow when the electrode was moved across the liver lobule with a micromanipulator. Lower rates of O2 uptake in pericentral areas were not altered appreciably by infusion of agents known to uncouple oxidative phosphorylation (DNP), increase ADP supply (fructose), or increase the NADH redox state (ethanol or octanoate). These data are consistent with the hypothesis that maximal rates of O2 uptake are regulated, in part, in the perfused liver by O2 concentrations far above the Km of cytochrome oxidase for O2.
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PMID:O2 uptake in periportal and pericentral regions of liver lobule in perfused liver. 371 41

Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose-6-phosphate, pyruvate, lactate), Krebs cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate), related free amino acids (glutamate, alanine), ammonia, energy store (creatine phosphate), energy mediators (ATP, ADP, AMP) and energy charge potential were evaluated. Furthermore the maximum rate (Vmax) of the following muscular enzyme activities was evaluated in the crude extract and/or mitochondrial fraction: for the anaerobic glycolytic pathway: hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase; for the tricarboxylic acid cycle: citrate synthase, malate dehydrogenase; for the electron transfer chain: total NADH cytochrome c reductase, cytochrome oxidase. The rat gastrocnemius muscles were analyzed in normoxia and after repeated, alternate hypoxic and normoxic exposures (12 hours of hypoxia daily; for 5 days). Naftidrofuryl was administered daily at three different doses: 10, 15 and 22.5 mg/kg i.m., 30 min before the beginning of the experimental hypoxia. The biochemical adaptation to intermittent normobaric hypoxic-normoxic exposures was characterized by the decrease of the muscular contents of creatine phosphate, citrate, alpha-ketoglutarate and glutamate. This adaptation occurred in absence of significant changes in the Vmax of the muscle enzymes tested. By naftidrofuryl treatment, in gastrocnemius muscle from hypoxic rats both alpha-ketoglutarate and creatine phosphate contents maintained normal values, while glutamate concentration remained reduced to subnormal values. With the exception of hexokinase, naftidrofuryl treatment did not modify the Vmax of marker enzymes related to energy transduction.
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PMID:Adaptation of skeletal muscle energy metabolism to repeated hypoxic-normoxic exposures and drug treatment. 401 59

Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose-6-phosphate, pyruvate, lactate), Krebs cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate), related free amino acids (glutamate, alanine), ammonia, energy store (creatine phosphate), energy mediators (ATP, ADP, AMP) and energy charge potential were evaluated. Furthermore the maximum rate (Vmax) of the following enzyme activities was evaluated in the crude extract and/or mitochondrial fraction: for the anaerobic glycolytic pathway: hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase; for the tricarboxylic acid cycle: citrate synthase, malate dehydrogenase; for the electron transfer chain: total NADH cytochrome c reductase, cytochrome oxidase. The rat gastrocnemius muscles were analysed in normoxia and after normobaric intermittent hypoxia (12 hours continuously daily; for 5 days). Cytidine and/or uridine were administered daily at the dose of 120 mg/kg, i.p., 30 min before the beginning of the experimental hypoxia. The intermittent normobaric hypoxia induced a biochemical adaptation characterized by the decrease of the muscular contents of creatine phosphate, citrate, alpha-ketoglutarate and glutamate. This adaptation occurred in the absence of significant changes in the Vmax of the tested muscle enzymes. In gastrocnemius muscle from hypoxic rats, the two biological pyrimidines tested induced various discrete, but often related, modifications of the contents of some Krebs cycle intermediates (i.e., alpha-ketoglutarate, malate) and related free amino acids (i.e., glutamate, alanine). In any case, the treatment with cytidine and/or uridine did not modify the Vmax of marker enzymes related to energy transduction.
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PMID:Modification of the skeletal muscle energy metabolism induced by intermittent normobaric hypoxia and treatment with biological pyrimidines. 402 89

This paper considers the way in which the oxygen reaction described by Dr. Nicholls and the ADP control reactions described by Dr. Racker could cooperate to establish a purposeful metabolic control phenomenon in vivo. This has required an examination of the kinetic properties of the respiratory chain with particular reference to methods for determinations of oxygen affinity (K(m)). The constant parameter for tissue respiration is k(1), the velocity constant for the reaction of oxygen with cytochrome oxidase. Not only is this quantity a constant for a particular tissue or mitochondria; it appears to vary little over a wide range of biological material, and for practical purposes a value of 5 x 10(7) at 25 degrees close to our original value (20) is found to apply with adequate accuracy for calculation of K(m) for mammalia. The quantity which will depend upon the tissue and its metabolic state is the value of K(m) itself, and K(m) may be as large as 0.5 microM and may fall to 0.05 microM or less in resting, controlled, or inhibited states. The control characteristic for ADP may depend upon the electron flux due to the cytochrome chain (40); less ADP is required to activate the slower electron transport at lower temperatures than at higher temperatures. The affinity constants for ADP control appear to be less dependent upon substrate supplied to the system. The balance of ADP and oxygen control in vivo is amply demonstrated experimentally and is dependent on the oxygen concentration as follows. In the presence of excess oxygen, control may be due to the ADP or phosphate (or substrate), and the kinetics of oxygen utilization will be independent of the oxygen concentration. As the oxygen concentration is diminished, hemoglobin becomes disoxygenated, deep gradients of oxygen concentration develop in the tissue, and eventually cytochrome oxidase becomes partially and then completely reduced. DPN at this point will become reduced and the electron flow diminished. The rate of ATP production falls and energy conservation previously under the control of the ADP concentration will now be controlled by the diffusion of oxygen to the respiratory enzymes in the mitochondria. Under these conditions the rate of reaction of cytochrome oxidase with oxygen and the reaction of cytochromes with one another become of key importance. The rise of ADP and the depletion of energy reserves evoke glycolytic activity, and failure of biological function may result.
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PMID:Reaction of oxygen with the respiratory chain in cells and tissues. 428 27

1. Mitochondria from ox heart and rat liver catalysed a slow cyanide-sensitive oxidation of 2,3-dimethylnaphthaquinol monophosphate, duroquinol monophosphate, menadiol 1-phosphate and menadiol 4-phosphate. 2. The release of P(i) was concomitant with oxygen uptake. 3. The oxidation was somewhat stimulated by Ca(2+) and P(i), and weakly inhibited by 2,4-dinitrophenol. 4. The quinol monophosphates effected a rapid reduction of free cytochrome c, and consequently addition of cytochrome c greatly increased the rate of the mitochondrial oxidation of 2,3-dimethylnaphthaquinol monophosphate. 5. This quinol phosphate interacts with the electron-transport chain at the level of cytochrome c. 6. Polylysine promoted an interaction between 2,3-dimethylnaphthaquinol monophosphate and cytochrome oxidase. Thus, although polylysine blocks mitochondrial oxidations via reduced cytochrome c, the oxidation of the quinol phosphate was strongly stimulated. 7. This stimulation was most effective in the most intact mitochondrial preparations and was inhibited by ADP and by P(i). 8. The implications of these results for factors limiting the rate of quinol phosphate oxidation, the mode of action of stimulators and the mechanism of P(i) formation are discussed.
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PMID:The mitochondrial oxidation of quinol monophosphates. 547 16

The growth plate chondrocyte plays a central role in growth plate function. The purpose of this study was to characterize the respiratory and calcium transport properties of isolated mammalian growth plate chondrocytes and mitochondria obtained from these cells and to quantitate the mitochondrial weight and volume fraction in each zone of the growth plate. A new method was developed for isolation of mitochondria from chondrocyte suspensions. Isolated chondrocyte mitochondria demonstrated an eightfold increase in oxygen consumption in response to calcium and a two- to threefold increase in oxygen consumption in response to adenosine diphosphate. Similar responses were observed in chondrocytes treated with digitonin. The mitochondrial protein content of the growth plate and hyaline cartilage chondrocytes is significantly less than hepatocytes. Conversely, the chondrocyte mitochondrial cytochrome aa3 content is similar to mitochondria from a wide variety of sources. A zonal analysis of the growth plate demonstrates an increase in the mitochondrial weight (protein) fraction from the reserve to the hypertrophic zone whereas the mitochondrial volume fraction decreases from the reserve to the hypertrophic zone. The findings of this study emphasize the dependence of chondrocytes on glycolysis as a prime energy source and support the concept that chondrocyte mitochondria have become specialized in the process of matrix calcification.
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PMID:Characterization of growth plate mitochondria. 609 92

Impairment of mitochondrial respiration in acute myocardial ischemia was studied in the inner and outer layers of canine heart muscle by the determination of oxidative phosphorylation and several respiratory enzymatic activities of isolated mitochondria. As early as 15 min after coronary ligation, the respiratory control ratio decreased as the result of a reduction in the oxygen consumption rate in state 3 to 72% of the control ratio in the inner layer. However, in the outer layer, it dropped to 74% after 1 to 2 hours. The oxygen consumption rate in state 4 and the ADP/O ratio were not significantly altered in both cardiac sublayers. In parallel with a decrease in oxygen consumption rate in state 3, Mg++-dependent ATPase and DNP-stimulated ATPase activities of isolated mitochondria reduced significantly in both sublayers, followed by a sequential increase in Mg++-dependent ATPase activity. Succinate dehydrogenase activity increased in ischemia for 3 hours in the inner layer, and for 6 hours in the outer layer, respectively; cytochrome oxidase activity reduced in both sublayers during the same period. Mitochondrial respiration is impaired in acute myocardial ischemia much earlier in the inner layer by a decrease in oxygen consumption rate in state 3, and there is a chronological delay in the development of ischemic mitochondrial changes in the outer myocardium.
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PMID:Regional changes in mitochondrial respiration in acute myocardial ischemia. Comparison of the inner and outer heart muscles. 609 79

The effect of lonidamine, an antispermatogenic and antitumor drug, on the oxygen consumption, ATPase activity, and redox state of the electron carriers of Ehrlich ascites tumor mitochondria has been studied. Lonidamine inhibits ADP- and uncoupler-stimulated respiration on various NAD- and FAD-linked substrates, but does not affect state 4 respiration. Experiments to determine its site of action showed that lonidamine does not significantly inhibit electron flow through cytochrome oxidase. Electron flow through site 2, the ubiquinone-cytochrome b-cytochrome c1 complex, also was unaffected by lonidamine, which failed to inhibit the oxidation of duroquinol. Moreover, inhibition of electron flow through site 2 was also excluded because of the inability of the N,N,N',N'-tetramethyl-p-phenylenediamine bypass to relieve the lonidamine inhibition of the oxidation of pyruvate + malate. The F0F1ATPase activity and vectorial H+ ejection are also unaffected by lonidamine. The inhibition of succinate oxidation by lonidamine was found to take place at a point between succinate and iron-sulfur center S3. Spectroscopic experiments demonstrated that lonidamine inhibits the reduction of mitochondrial NAD+ by pyruvate + malate and other NAD-linked substrates in the transition from state 1 to state 4. However, lonidamine does not inhibit reduction of added NAD+ by submitochondrial vesicles or by soluble purified NAD-linked dehydrogenases. These observations, together with other evidence, suggest that electron transport in tumor mitochondria is inhibited by lonidamine at the dehydrogenase-coenzyme level, particularly when the electron carriers are in a relatively oxidized state and/or when the inner membrane-matrix compartment is in the condensed state. The action of lonidamine in several respects resembles the selective inhibition of electron transport in tumor cells produced by cytotoxic macrophages (D. L. Granger and A. L. Lehninger (1982) J. Cell Biol. 95, 527).
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PMID:Action of the antitumor and antispermatogenic agent lonidamine on electron transport in Ehrlich ascites tumor mitochondria. 622 86


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