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)

A method was developed for selecting cytochrome-deficient mutants of yeast Candida parapsilosis; the method is based on determining the rate of inhibition of oxygen uptake by benzhydroxamic acid, an inhibitor of cyanide-resistant oxidase in the cells of preliminarily obtained yeast mutants. The mutant (C. parapsilosis bhas-1) lacks cytochrome a+a3, contains the same quantity of cytochrome b as the wild strain and a twice as low quantity of cytochrome c. In contrast to the wild strain, the mutant does not grow on ethanol for the first two days but, being cultivated further (up to 5 days), in a medium with ethanol, it resumes its capability to utilize ethanol as a carbon and energy source. Prolonged cultivation in the medium with ethanol induces the biosynthesis of cytochrome oxidase while cytochrome a+a3 is not induced in a medium supplied with glucose. The biomass accumulated by the mutant in the medium with glucose is twice as low comparing to that of the wild strain. The oxidative activity of the mutant mitochondria involves cyanide, resistant oxidase. The mitochondria of the mutant oxidize NAD-dependent substrates, NADH, NADPH, succinate, alpha-glycerophosphate, ethanol and lactate. The mitochondria have a low respiratory control and phosphorylate ADP while oxidizing NAD-dependent substrates, ethanol and lactate, but not alpha-glycerophosphate, succinate, NADH and NADPH.
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PMID:[Selection method and the characteristics of a cytochrome (a+a3)-deficient mutant of Candida parapsilosis yeasts]. 702 49

A delay in the onset of accumulation of methylene hexadecanoic acid could be engendered in Pseudomonas denitrificans growing under limited oxygen conditions when the concentration of citrate but not the concentration of succinate in the medium was increased from 0.1 to 0.5%. Ascorbate, which specifically reduced a cytochrome component possessing a maximum absorbance at 551 nm, partially inhibited the accumulation of methylene hexadecanoic acid under conditions which otherwise led to maximal production. Limiting terminal cytochrome oxidase activity by controlling the oxygen supply, or by the use of low concentrations of the oxidase inhibitors cyanide or azide also prevented the accumulation of the fatty acid regardless of the nature or concentration of carbon source in the medium. Measurement of the levels of ATP, NAD and NADH as well as the steady state of reduction of respiratory components in vivo showed that the onset of accumulation of methylene hexadecanoic acid could be specifically correlated with the state of reduction of respiratory components. The uniqueness of succinate respiration in promoting the synthesis of cyclopropane synthetase (unsaturated-phospholipid methyltransferase (EC 2.1.1.16) under limited oxygen conditions could therefore be assigned to the high degree of oxidation of respiratory components observed under this condition.
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PMID:Studies on cyclopropane fatty acid synthesis. Correlation between the state of reduction of respiratory components and the accumulation of methylene hexadecanoic acid by Pseudomonas denitrificans. 728 25

Cations caused a decrease in the apparent Km and an increase in the Vmax. for the oxidation of exogenous NADH by both Jerusalem-artichoke (Helianthus tuberosus) and Arum maculatum (cuckoo-pint) mitochondria prepared and suspended in a low-cation medium (approximately or equal to 1 mM-K+). In Arum mitochondria the addition of cations caused a much greater stimulation of the oxidation of NAD(P)H via the cytochrome oxidase pathway than via the alternative, antimycin-insensitive, pathway. This shows that cations affected a rate-limiting step in the electron-transport chain at or beyond ubiquinone, the branch-point of electron transport in plant mitochondria. The effects were only dependent on the valency of the cation (efficiency C3+ greater than C2+ greater than C+) and not on its chemical nature, which is consistent with the theory of the diffuse layer. The results are interpreted to show that the screening of fixed negative membrane changes on lipids and protein complexes causes a conformational change in the mitochondrial inner membrane, leading to a change in a rate-limiting step of NAD(P)H oxidation. More specifically, it is proposed that screening removes electrostatic restrictions on lateral diffusion and thus accelerates diffusion-limited steps in electron transport.
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PMID:Charge screening by cations affects the conformation of the mitochondrial inner membrane. A study of exogenous MAD(P)H oxidation in plant mitochondria. 731 73

Mitochondria from skeletal muscle, heart and liver of strain 129/ReJ-dy dystrophic mice and their littermate controls were characterized with respect to their respiratory and phosphorylating activities. Skeletal muscle mitochondria from dystrophic mice showed significantly lower state 3 respiratory rates than controls with both pyruvate + malate and succinate as substrates (P less than 0.01). ADP/O and Ca2+/O ratios were found to be normal. A decreased rate of NADH oxidation (0.01 less than P less than 0.05) by sonicated mitochondrial suspensions from dystrophic mice was also seen. High respiratory rates with ascorbate + phenazine methosulfate as substrates indicated that cytochrome oxidase was not rate limiting in the oxidation of either pyruvate + malate or succinate. Skeletal muscle mitochondria from dystrophic mice showed no deficiency in any of the cytochromes or coenzyme Q. Mg2+-stimulated ATPase activity was higher in dystrophic muscle mitochondria than in controls, but basal and oligomycin-insensitive activities were virtually identical to those of controls. A significant reduction inthe intramitochondrial NAD+ content (0.01 less than P less than 0.02) was seen in dystrophic skeletal muscle as compared to controls. Heart mitochondria from dystrophic mice showed similar, though less extensive abnormalities while liver mitochondria were essentially normal. We concluded from these results that skeletal muscle mitochondria from strain 129 dystrophic mice possess impairments in substrate utilization which may result from (1) an abnormality in the transfer of electrons on the substrate side of coenzyme Q in the case of succinate oxidation; (2) a defect on the path of electron flow from NADH to cytochrome c, and (3) a deficiency of NAD+ in the case of NAD+-linked substrates.
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PMID:Impaired substrate utilization in mitochondria from strain 129 dystrophic mice. 735 83

Fluorometry and dual-wave-length spectrophotometry were used to detect transitory shifts in the redox state of mitochondrial NADH and cytochrome aa3 in the exposed cerebral cortex of anesthetized paralyzed cats as seizures were induced with pentylenetetrazol. In normotensive animals, NADH and cytochrome aa3 oxidation accompany the seizures, but when the mean arterial pressure (MAP) is reduced to 40.2 +/- 1.1% of the base line by hemorrhaging, the NADH fluorescence response converts to a biphasic oxidation-reduction sequence. In extreme hypotension (MAP lowered to an average of 28%), only NAD reduction transients are observed with seizures, and cytochrome aa3 is oxidized irrespective of the low MAP. Our data show that a reversible perfusion impairment, perhaps inhomogeneous in its distribution, appears in the cortex at the 40% MAP level and modifies electron flux in the respiratory chain between NADH and cytochrome aa3, and uniform oxygen insufficiency is an unlikely cause for the reversal of NADH oxidation toward reduction during seizures under hypovolemic conditions.
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PMID:Redox transitions in mitochondria of cat cerebral cortex with seizures and hemorrhagic hypotension. 736 22

The effect of reperfusion following 30 min of cerebral ischaemia on brain mitochondrial respiratory chain activity has been studied in the gerbil. The state 3 respiration rates with both FAD- and NAD-linked substrates were reduced after ischaemia. After 5 min of reperfusion, state 3 respiration with FAD-linked substrates was restored, but levels of NAD-linked substrates did not return to control values until 30 min of reperfusion. By 120 min of reperfusion state 3 respiration decreased relative to control values with all substrates studied. Measurement of the individual respiratory chain complexes showed that complex I, complex II-III, and complex V activities were reduced after ischaemia. By 5 min of reperfusion complex II-III activity was restored, but the activities of complexes I and V did not return to control values until 30 min of reperfusion. In contrast, complex IV activity was unaffected by ischaemia or 5 and 30 min of reperfusion but was significantly reduced after 120 min of reperfusion, possibly owing to free radical production and lipid peroxidation.
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PMID:Effect of reperfusion following cerebral ischaemia on the activity of the mitochondrial respiratory chain in the gerbil brain. 756 67

During acute (< 30 min) hypoxia, cellular respiration is independent of the O2 concentration as long as PO2 remains above a critical value (5-10 Torr). Similarly, state 3 respiration by isolated mitochondria is independent of PO2 above a critical tension of 2-4 Torr. However, rat hepatocytes demonstrate a reversible suppression of respiration and an increase in NAD(P)H concentration during prolonged (2-24 h), but not acute hypoxia [P. T. Schumacker, N. Chandel, and A. G. N. Augusti. Am. J. Physiol. 265 (Lung Cell. Mol. Physiol. 9): L395-L402, 1993]. This study tested whether respiration is similarly inhibited in isolated mitochondria exposed to low PO2 for prolonged periods and whether cytochrome-c oxidase participates in this response. Coupled rat liver mitochondria were incubated under low oxygen conditions (PO2 < 2 Torr) for 2 h. State 3 respiration after reoxygenation to PO2 = 20 Torr was then compared with the value obtained subsequently at 100 Torr. Using succinate and ADP as substrates, we determined that state 3 respiration at 20 Torr was 61.0 +/- 8.4% of the subsequent value at 100 Torr (P < 0.05). By contrast, control mitochondria reoxygenated to 100 Torr first and 20 Torr subsequently showed no significant difference at the two O2 tensions (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of cytochrome-c oxidase activity during prolonged hypoxia. 761 33

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

1. Cetaben in contrast to fibrates affect differently peroxisomal constituents. 2. Changes in large scale of liver non-peroxisomal parameters were compared after 10 days administration of equal doses (200 mg/kg/day) of cetaben and clofibric acid to male Wistar rats. 3. Clofibric acid treatment increased markedly the activities of FAD-glycerol-3-P dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, cytochrome-c oxidase, malic enzyme, NAD-glycerol-3-P dehydrogenase, ethoxycoumarin deethylase, p-nitroanisole demethylase and amounts of cytochrome P-450 and b5. 4. However no analogical changes were observed after cetaben treatment in the livers of experimental animals. 5. Both drugs increased the activities of alanine-glyoxylate aminotransferase-1 and acetylcarnitine transferase--enzymes with proven mitochondrial and peroxisomal location. 6. Cetaben contrary to clofibric acid does not increase solubilization of peroxisomal enzymes. 7. Enhanced acetylcarnitine transferase and alanine-glyoxylate aminotransferase-1 activities were distributed in mitochondria as well as in peroxisomes after clofibric acid treatment, however, only peroxisomes were enriched after cetaben administration. 8. The results obtained suggest that cetaben represents an exceptional type of peroxisome proliferator, specifically affecting peroxisomes, without having a negative influence on the processes of peroxisome biogenesis.
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PMID:Cetaben is an exceptional type of peroxisome proliferator. 800 53

The present study deals with the in vitro and in vivo effects of methyl isocyanate (MIC) on rat brain mitochondrial function. Addition of MIC to tightly coupled brain mitochondria in vitro resulted in a mild stimulation of state 4 respiration, abolition of respiratory control, decrease in ADP/O ratio, and inhibition of state 3 oxidation. The oxidation of NAD(+)-linked substrates (glutamate + malate) was more sensitive (fourfold) to the inhibitory action of MIC than succinate while cytochrome oxidase was unaffected. Administration of MIC subcutaneously at a lethal dose affected respiration only with glutamate+malate as the substrate (site I) and caused a 20% decrease in state 3 oxidation leading to a significant decrease in respiratory control index while state 4 respiration and ADP/O ratio remained unaffected. As both the malondialdehyde and iron contents of brain mitochondria were not altered, it may be inferred that the observed in vivo inhibition of state 3 oxidation is induced by MIC through systemic stagnant hypoxia leading to ischemia of brain, which further contributes to the cerebral hypoxia.
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PMID:In vitro and in vivo effects of methyl isocyanate on rat brain mitochondrial respiration. 806 Jan 73


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