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)

Purified beef heart cytochrome-c oxidase preparations derived by three different laboratories contain NADH-K3 Fe (CN)6, NADH-nitrobluetetrazolium, and NADPH-nitrobluetetrazolium reductases. This is true of preparations exhibiting heme aa3 to protein ratios considered indicative of an excellent purity. An apparent association of cytochrome-c oxidase and one or more of the contaminants persists through immunodiffusion and nondenaturing electrophoresis and, in addition, in one instance copurification of NADH-K3Fe(CN)6 reductase and cytochrome-c oxidase to a constant ratio of specific activities was demonstrated. Cytochrome-c oxidase can be freed of the contaminants by equilibration with an NAD+-affinity matrix. As aconcomitant of equilibration with the matrix, the KM of cytochrome-c oxidase for ferrocytochrome-c is invariably decreased. Rat constants at low ferrocytochrome-c concentrations are consistently enhanced in all oxidase preparations upon equilibration with the NAD+ matrix. However, the effects of such equilibrations on the extrapolated Vmax varies from one preparation to another. Polyacrylamide gel electrophoresis in SDS-urea systems establishes that each of the preparations contains a minimum of three contaminants, each of an apparent formula weight of greater than 40,000 Daltons. NADH-NBT reductase was found to have a formula weight of approximately 46,000 Daltons. Their properties establish that NADH-K3Fe(CN)6 and NADH-NBT reductases are separate proteins; the separate identity of NADPH-NBT reductase has not yet been determined.
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PMID:Evidence for the presence of di- and triphospho pyridine nucleotide dehydrogenase derivatives as consistent contaminants of purified beef heart cytochrome-c oxidase. 18 83

Isolated rat heart was perfused with Langendorff's retrograde perfusion method, while the oxygen consumption and the left ventricular pressure were monitored continually. The steady-state contents of metabolites in the cardiac tissue, freeze clamped under various work-load conditions, were determined and the concentrations of free cytosolic ADP and AMP were calculated from the near equilibrium in creatine phosphokinase and adenylate kinase reactions. Increasing respiratory rate with increasing load was accompanied by a fall in the cytosolic free [ATP]/[ADP][Pi] but little change in the mitochondrial free [NAD+]/[NADH]. The free energy of ATP hydrolysis was calculated from the concentrations of the adenine nucleotides and compared with the values computed from the measured turnover number for cytochrome c and redox state of the mitochondrial NAD couple according to a mathematical model. The agreement between the two values was good over a wide range of metabolic conditions, which provides further support for the proposed near-equilibrium model of mitochondrial respiration with control exerted at the cytochrome oxidase-oxygen reaction.
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PMID:Energy relationships between cytosolic metabolism and mitochondrial respiration in rat heart. 20 95

We have seen that there is no simple answer to the question 'what controls respiration?' The answer varies with (a) the size of the system examined (mitochondria, cell or organ), (b) the conditions (rate of ATP use, level of hormonal stimulation), and (c) the particular organ examined. Of the various theories of control of respiration outlined in the introduction the ideas of Chance & Williams (1955, 1956) give the basic mechanism of how respiration is regulated. Increased ATP usage can cause increased respiration and ATP synthesis by mass action in all the main tissues. Superimposed on this basic mechanism is calcium control of matrix dehydrogenases (at least in heart and liver), and possibly also of the respiratory chain (at least in liver) and ATP synthase (at least in heart). In many tissues calcium also stimulates ATP usage directly; thus calcium may stimulate energy metabolism at (at least) four possible sites, the importance of each regulation varying with tissue. Regulation of multiple sites may occur (from a teleological point of view) because: (a) energy metabolism is branched and thus proportionate regulation of branches is required in order to maintain constant fluxes to branches (e.g. to proton leak or different ATP uses); and/or (b) control over fluxes is shared by a number of reactions, so that large increases in flux requires stimulation at multiple sites because each site has relatively little control. Control may be distributed throughout energy metabolism, possibly due to the necessity of minimizing cell protein levels (see Brown, 1991). The idea that energy metabolism is regulated by energy charge (as proposed by Atkinson, 1968, 1977) is misleading in mammals. Neither mitochondrial ATP synthesis nor cellular ATP usage is a unique function of energy charge as AMP is not a significant regulator (see for example Erecinska et al., 1977). The near-equilibrium hypothesis of Klingenberg (1961) and Erecinska & Wilson (1982) is partially correct in that oxidative phosphorylation is often close to equilibrium (apart from cytochrome oxidase) and as a consequence respiration and ATP synthesis are mainly regulated by (a) the phosphorylation potential, and (b) the NADH/NAD+ ratio. However, oxidative phosphorylation is not always close to equilibrium, at least in isolated mitochondria, and relative proximity to equilibrium does not prevent the respiratory chain, the proton leak, the ATP synthase and ANC having significant control over the fluxes. Thus in some conditions respiration rate correlates better with [ADP] than with phosphorylation potential, and may be relatively insensitive to mitochondrial NADH/NAD+ ratio.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Control of respiration and ATP synthesis in mammalian mitochondria and cells. 159 89

The activities of enzymes related to energy metabolism in the gastrocnemius and soleus muscles in young-adult (4 months), mature (12 months), and senescent (24 months) rats were compared after continuous (72 consecutive h) exposure to normobaric hypoxia or normoxia after the vasodilator naftidrofuryl or saline solution had been given intraperitoneally for 30 consecutive days. The maximum rats (Vmax) of the following enzyme activities in the crude extract and/or the crude mitochondrial fraction of each muscle specimen were evaluated for: the anaerobic glycolytic pathway (hexokinase, phosphofructokinase, pyruvate kinase, and lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthase, and malate dehydrogenase), the electron transfer chain (cytochrome oxidase), and the NAD+/NADH redox state (total NADH cytochrome c reductase). The significance of differences between the enzyme activities at different ages or under different experimental conditions in the two tissue preparations of the two muscles were determined by ANOVA. MCA and ETA2 were used to evaluate the net effects of the experimental conditions. First, aging did not seem to affect the soleus and gastrocnemius muscles in the same way. In the gastrocnemius muscle, the major changes were seen in enzymes of the glycolytic pathway, in the crude extracts. In the soleus muscle, the more striking changes in enzyme activities as a function of aging were found in the crude mitochondrial fraction. We also found that hypoxia caused more important changes in 12-month-old rats than in those of other ages (especially the enzyme activities of the gastrocnemius muscle). Naftidrofuryl modified the effects of hypoxia only sometimes and further investigations are necessary before we can draw any conclusions about the pharmacological activity of naftidrofuryl in hypoxia.
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PMID:Effects of hypoxia and pharmacological treatment on enzyme activities in skeletal muscle of rats of different ages. 164 27

Patients treated for aneurysmal subarachnoid hemorrhage show, in the long-term follow up, an elevated rate of cognitive disturbances that are mainly related to the impact of the initial bleeding: the neurotoxic effects of blood deposition in subarachnoidal spaces may result in a diffuse encephalopathy, but the intrinsic mechanism and the biochemical correlates are not known. In the present study we have evaluated mitochondrial function after experimental induction of subarachnoid hemorrhage. Mitochondrial function was evaluated in four different rat brain areas (frontal cortex, occipital cortex, hippocampus, and brain stem) after experimental isobaric subarachnoid hemorrhage in rats. Subarachnoid hemorrhage was induced by injecting 0.07 mL of arterial autologous blood into the cisterna magna. Intracranial pressure did not significantly increase. The nonsynaptic mitochondrial fraction was isolated from different rat brain areas, and the maximal rate of enzymatic reactions of some key enzymatic activities related to the Krebs cycle [nicotinamide adenine dinucleotide (oxidized form) (NAD+)-isocitrate dehydrogenase, citrate synthase, and succinate dehydrogenase] and of the electron transfer chain (cytochrome oxidase) were evaluated. The nonsynaptic mitochondrial fraction was utilized also to check parameters related to the mitochondrial respiration: state 3, state 4, uncoupled state, respiratory control ratio, and adenosine 5'-diphosphate/oxygen ratio. The biochemical parameters were measured at 1 and 72 hours after the subarachnoidal injection of blood. Subarachnoid hemorrhage did not affect the mitochondrial enzymatic activities both at 1 and 72 hours, while the mitochondrial enzymatic activities parameters were significantly affected: in particular, a significant decrease of respiratory control ratio in all tested brain areas was demonstrated. The increased mitochondrial vulnerability in the delayed phases could be one of the biochemical correlates of post-hemorrhagic encephalopathy.
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PMID:Experimental isobaric subarachnoid hemorrhage: regional mitochondrial function during the acute and late phase. 221 48

The oxygen dependence of hepatic cellular respiration was studied by employing simultaneous organ spectrophotometry of cytochromes and hemoglobin, the latter used as an intrasinusoidal optical oxygen probe. The Km of cytochrome aa3 for oxygen was found to be 6.8 microM in the isolated perfused liver and 0.3 microM in suspensions of isolated hepatocytes. The results indicate that the sinusoid-to-cell pO2 gradient is about 5 torr. Optical determination of the average effective pO2 indicates that the axial sinusoidal O2 profile does not conform to zero-order O2 uptake in the liver. Because of extensive NAD+ reduction, ethanol increases the thermodynamic driving force of oxidative phosphorylation, and it also increased the oxygen consumption in both the perfused liver and the hepatocyte suspension, but had no effect on the grade of steady-state cytochrome aa3 reduction, the cellular energy state [ATP]/[ADP].[Pi], or the Km of cytochrome aa3 for oxygen. The results indicate that hepatic energy metabolism is oxygen independent at very low O2 concentrations, but that the sinusoidal axial O2 concentration is anomalous, probably due to the spatial arrangement of the metabolizing systems.
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PMID:Oxygen and substrate dependence of hepatic cellular respiration: sinusoidal oxygen gradient and effects of ethanol in isolated perfused liver and hepatocytes. 282 30

Since many metabolic derangements induced by ethanol have been linked to the redox shift, we studied the effects of oxygen in the range of tensions prevailing in vivo along the sinusoids on both the basal redox state and the shift induced by ethanol. The redox state of nicotinamide nucleotides was assessed by surface NADH fluorescence and that of cytochrome oxidase by transmittance dual-wavelength spectrophotometry in the hemoglobin-free, perfused rat liver. In the absence of ethanol, varying the oxygen tensions within the physiological range produced a redox gradient of both cytochrome oxidase and NAD+, with a more reduced state at tensions normally prevailing in perivenular zones. The degree of reduction of cytochrome oxidase at these physiological oxygen tensions was associated with no impairment in the ability of the liver to consume oxygen and to produce ATP, suggesting lack of cellular anoxia. 25 mM ethanol increased hepatic oxygen consumption, but had no direct effect on the state of reduction of cytochrome oxidase. The effects of ethanol and oxygen tensions on NADH fluorescence were additive, indicating that a greater redox shift should occur when ethanol is oxidized at oxygen tensions similar to those normally prevailing in prievenular zones than at those in periportal zones. This dependence of the ethanol-induced redox shift on oxygen tensions may contribute to the selective perivenular hepatotoxicity of alcohol.
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PMID:Dependence of ethanol-induced redox shift on hepatic oxygen tensions prevailing in vivo. 299 May 1

Blue and non-blue states of the copper center in copper-substituted alcohol dehydrogenase (EC 1.1.1.1) can be attained by coenzyme binding and/or ligand binding to the copper ion. Copper alcohol dehydrogenase has been studied by electronic absorption, CD and EPR spectroscopy in the presence and absence of coenzyme. On the basis of previous work on blue (Type 1) copper proteins with a CuSS*N2 chromophore the assignment of charge transfer transitions in copper alcohol dehydrogenase is discussed. The latter contains a CuS2N(OH2) unit in the ligand-free protein and a CuS2N2 unit in the ternary complex with NAD+ and pyrazole. It is proposed that the energy of the charge transfer transitions can be used as a structural marker in combination with EPR data. A comparison is made between the spectroscopic properties of the ternary complex of copper alcohol dehydrogenase and the copper centers in stellacyanin and cytochrome-c oxidase (CuA) in order to test the validity of recent structural models of the type CuS2N2, i.e., a cupric ion coordinated to two thiolate ligands. Finally, a close resemblance between the electronic absorption spectra of copper alcohol dehydrogenase and those of other variants of Type 1 copper centers such as the 'unusual' copper center of nitrous oxide reductase is noted as an indication of similar coordination environments.
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PMID:Electronic absorption and EPR spectroscopy of copper alcohol dehydrogenase: pink, violet and green forms of a type 1 copper center analog. 303 63

The effect of hypoxia and post-hypoxic recovery were studied in gastrocnemius muscle of young-adult and mature beagle dogs. Furthermore, the possible interference of pharmacological treatment with nicergoline was evaluated in these conditions. Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose 6-phosphate, pyruvate, lactate), Kreb's cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate) and related free amino acids (glutamate, alanine), ammonium ion, energy store and mediators (ATP, ADP, AMP and creatine phosphate), and the energy charge potential were evaluated. Furthermore, in the crude extract and/or mitochondrial fraction of another portion of the same gastrocnemius muscle the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway (hexokinase, lactate dehydrogenase), the Kreb's cycle (citrate synthase, malate dehydrogenase), the aminoacid pool related to the Krebs' cycle (glutamate dehydrogenase and aspartate aminotransferase), the electron transfer chain (cytochrome oxidase) and NAD+/NADH exchanges (total NADH cytochrome c reductase) was evaluated. Some glycolytic metabolites and Krebs' cycle intermediates were modified by acute hypoxia, while free amino acids and energy mediators remained practically unchanged. The pharmacological treatment maintained the glucose and succinate muscular concentrations within the normal range, during hypoxia. The behaviour of muscular metabolites during hypoxia and/or post-hypoxic recovery is an age-related event. In fact, only in young-adult animals did the altered values return to normal in post-hypoxic recovery. In the present experimental conditions, only minor changes were observed as far as muscular enzyme activities are concerned. In any case, some enzyme activities tested showed different Vmax in young-adult dogs in comparison with mature ones.
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PMID:Effect of hypoxia, aging and pharmacological treatment on muscular metabolites and enzyme activities. 322 9

Enzyme histochemical methods were performed on sporozoite infected liver tissue of rats in order to gain insight into the nutrition and metabolism of exoerythrocytic forms of Plasmodium berghei. The following enzymes were demonstrated in the hepatocytic stages of the parasites, obtained 41 and 48 h after inoculation of sporozoites: acid phosphatase, cytochrome oxidase, NADH-tetrazolium reductase, succinate dehydrogenase, NAD+ and NADP+ dependent isocitrate dehydrogenase, NADP+-dependent malate dehydrogenase, lactate dehydrogenases, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenases and alpha-glycerol-phosphate dehydrogenase. The results suggest that a conventional Embden-Meyerhoff pathway, pentose phosphate pathway and Krebs' citric acid cycle may in part be present in these exoerythrocytic parasites. Alkaline phosphatase, nucleoside polyphosphatase, 5' nucleotidase, glucose-6-phosphatase, alpha-glucan phosphorylase, NAD+ dependent malate dehydrogenase, amino-peptidase M and non-specific esterases were not detected by our techniques in the parasite. The enzyme distribution of this intrahepatocytic malaria parasite revealed by histochemistry is compared with the enzyme distribution in the other phases of the parasite's life cycle.
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PMID:Histochemical observations on the exoerythrocytic malaria parasite Plasmodium berghei in rat liver. 608 94


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