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 bioenergetic pattern of a cell clone derived from rat lung with ultrastructural and biochemical characteristics like those of type II pneumocytes (T-II-P), has been studied in a tissue culture system. During air cultivation, these cells have a high rate of aerobic and anaerobic glycolysis associated with high activities of two rate-limiting enzymes in glycolysis (pyruvate kinase [PyKi] and phosphofructokinase [PFK]). This is present despite the rates of oxygen consumption and activities of cytochrome oxidase (CyOx) similar to other lung cells. Presumably the high rate of aerobic glycolysis explains the substantial lactate production previously described in lung slices and in the intact perfused lung. Hypoxic cultivation results in a decrease in CyOx. Acute re-exposure to air does not restore the oxygen consumption to normal, presumably as a result of decreased mitochondrial O(2) utilization associated with decreased CyOx activity. As a result, hypoxically cultivated T-II-P cells have a decreased capacity for mitochondrial ATP generation in air as compared to air-cultivated cells. During hypoxia, aerobic and anaerobic glycolysis are further increased as well as the activities of PyKi and PFK. The high rate of glycolysis and high activities of PyKi and PFK in cultivated T-II-P appear to reflect intrinsic genetic regulation. The decreased CyOx activity and increased PyKi and PFK activities in hypoxic T-II-P appear to reflect alterations in enzyme biosynthesis/biodegradation regulated by O(2) availability.
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PMID:Bioenergetic pattern of isolated type II pneumocytes in air and during hypoxia. 20 32

Oxidation of exogenous NADH in mitochondria isolated from wild type and mi-1 mutant of Neurospora crassa decreases rapidly in vitro. In mi-1 mutant mitochondria the inactivation concerns the alternate pathway of oxidation whereas in the wild type it involves an unknown component of the respiratory chain. The activity of the primary NADH dehydrogenase is constant within the time of the experiments (2-4 h). NADH oxidase is not inactivated if oxygen is removed from the incubation medium by nitrogen bubbling. Succinate oxidase does not show any remarkable changes in activity within 2-3 h. In fresh mitochondria of the mi-1 mutant reduced ubiquinone is completely reoxidized by cytochrome oxidase but only 80% reoxidized by the alternate oxidase. In aged mitochondria of the mi-1 mutant in the presence of cyanide, ubiquinone is reduced to the level characteristic for fresh mitochondria in which respiration is completely inhibited by cyanide plus salicylhydroxamic acid. In these mitochondria the reoxidation of the reduced ubiquinone proceeds only via the cytochrome pathway. It is supposed that a labile component(s) of the respiratory chain present in the mi-1 mutant and the wild type mitochondria may, in mi-1 mutant, act as an alternate oxidase.
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PMID:Disappearance of the cyanide-insensitive pathway of oxidation in mitochondria of MI-1 mutant of Neurospora crassa in vitro. 20 34

The ability of various native and modified cytochromes c to transfer electrons to cytochrome oxidase is compared in cytochrome c depleted beef heart mitochondrial particles. The kinetics are followed at -49 degrees C after the reaction is initiated by photolysis of the CO compound of cytochrome oxidase in the presence of oxygen. Horse, human, yeast iso-2, and carboxydinitrophenyl (CDNP)-lysine-60 horse cytochromes c all give initial rates of electron transfer that are equal to those observed in whole beef mitochondria. Euglena, CDNP-lysine-72, and CDNP-lysine-13 horse cytochromes c give rates about one-tenth that of whole mitochondria. These rates were independent of the concentration of cytochrome c. Since the inhibited cytochromes c, but not the active proteins, had previously been shown to have lowered affinity for cytochrome oxidase, the results indicate that the structural characteristics important for the association of cytochrome c and oxidase are also essential for achieving normal rates of electron transfer within the complex once formed.
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PMID:Low-temperature studies of electron transfer between different cytochromes c and cytochrome c oxidase. 20 99

Cytochrome oxidase forms two distinctive compounds with oxygen at --105 and --90 degrees C, one appears to be oxycytochrome oxidase (Compound A) and the other peroxycytochrome oxidase (Compound B). The functional role of compound B in the oxidation of cytochrome c has been examined in a variety of mitochondrial preparations. The rate and the extent of the reaction have been found to be dependent upon the presence of a fluid phase in the vicinity of the site of the reaction of cytochrome c and cytochrome oxidase. The kinetics of cytochrome c oxidation and of the slowly reacting component of cytochrome oxidase are found to be linked to one another even in cytochrome c depleted preparations, but under appropriate conditions, especially low temperatures, the oxidation of cytochrome c precedes that of this component of cytochrome oxidase. Based upon the identification of the slowly reacting components of cytochrome oxidase with cytochrome c, various mechanisms are considered which allow cytochrome c to be oxidized without the intervention of cytochrome a at very low temperatures, and tunneling seems an appropriate mechanism.
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PMID:Cytochrome c-cytochrome oxidase interaction at subzero temperatures. 20 1

The effect of pre-energization of isolated mitochondria by ATP at room temperature upon the kinetics of oxygen intermediates (measured at very low temperatures) of cytochrome c oxidase has been studied. It was found that "energization" of mitochondria at room temperature had dramatic effects on several partial reactions of cytochrome aa3. Thus, in the "energized" frozen state, the rate of O2 binding to ferrous cytochrome a3 and the subsequent formation of the "peroxy" compound B are accelerated, while oxidation of cytochromes c and c1 is inhibited. These effects of ATP are abolished by oligomycin and uncoupling agents and may, therefore, be reflections of the coupling of the mitochondrial ATP synthetase to the respiratory chain at the level of cytochrome c oxidase, which is the basis of the mechanism of coupling respiration to ATP synthesis and respiratory control.
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PMID:The effect of mitochondrial energization on cytochrome c oxidase kinetics as measured at low temperatures. II. The binding and reduction of dioxygen. 20 3

The heat resistance of the oxygen consumption by the mitochondria, temperature dependence of the Michaelis' constant (CM) and heat resistance of cytochrome oxidase were studied in the embryos and larvae of fish hybrids (Misgurnus X Brachydanio). The oxygen consumption by the mitochondria from the larvae of Misgurnus ceased (following the 10 min heating) at 50 degrees, from Brachydanio at 54 degrees and from the hybrids at 52 degress suggesting control of the respiratory function. CM of cytochrome oxidase has the same minimum in the larvae of Misgurnus and Brachydanio, therefore this criterion was not used to study the genetic control in their hybrids. The heat resistance of cytochrome oxidase (T50) differed in Misgurnus and Brachydanio and was of intermediate value in their hybrids. At the early stages of hybrid development T50 was of maternal type (Misgurnus) but beginning from the mid-gastrula stage T50 increased and attained the maximum prior to the hatching. Chloramphenicol did not affect the increase of T50 in hybrids, but actinomycin decreased it almost down to the level characteristic of Misgurnus. The data obtained suggest that the genetic control of cytochrome oxidase activity begins earlier than that of other studied enzymes.
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PMID:[Expression of paternal genes controlling cytochrome oxidase activity in hybrid fish]. 20 80

The reaction of ascorbate-reduced Pseudomonas cytochrome oxidase with oxygen was studied by using stopped-flow techniques at pH 7.0 and 25 degrees C. The observed time courses were complex, the reaction consisting of three phases. Of these, only the fastest process, with a second-order rate constant of 3.3 X 10(4) M-1.S-1, was dependent on oxygen concentration. The two slower processes were first-order reactions with rates of 1.0 +/- 0.4s-1 and 0.1 +/- 0.03s-1. A kinetic titration experiment revealed that the enzyme had a relatively low affinity constant for oxygen, approx. 10(4)M-1. Kinetic difference spectra were determined for all three reaction phases, showing each to have different characteristics. The fast-phase difference spectrum showed that changes occurred at both the haem c and haem d1 components of the enzyme during this process. These changes were consistent with the haem c becoming oxidized, but with the haem d1 assuming a form that did not correspond to the normal oxidized state, a situation that was not restored even after the second kinetic phase, which reflected further changes in the haem d1 component. The results are discussed in terms of a kinetic scheme.
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PMID:The reaction of Pseudomonas aeruginosa cytochrome c-551 oxidase with oxygen. 21 Jul 64

In order to investigate the effects of high concentrations of oxygen on the lung, experiments were performed on 18 baboons exposed to a humidified environment of 95% oxygen for five days. Open lung biopsies for biochemical assay, histologic and electron microscopic analysis and measurement of tissue respiration were performed before and after oxygen exposure. Pulmonary function was evaluated by measurement of arterial blood gases, compliance, closing capacity (CC), functional residual capacity (FRC), total lung capacity (TLC), residual volume (RV) and vital capacity (VC) before and after exposure and then at seven and 14 days in the animals which recovered. Six baboons removed from the oxygen environment after 96--110 hours and exposed to room air died within three to 20 hours of profound hypoxemia (PaO2 40 +/- 6). The remaining 12 baboons were successfully weaned to room air over a three day period with a return of ABGs to control values (PaO2 89+/- 2). Electron microscopic analysis of alveolar membranes exposed to 120 hours of hyperoxia demonstrated endothelial cell swelling, interstitial alveolar membrane edema, and an increased predominance of Type II pneumocytes. Lung volume measurements showed significant decreases in TLC (25%), VC (34%), CC/TLC (28%) and dynamic compliance (47%). Biochemical studies indicated a shift toward anaerobic metabolism with a decrese in tissue oxygen consumption, reduced cytochrome oxidase activity, and increased lung lactic acid production. These changes were all found to be reversible in the 12 baboons slowly weaned back to room air.
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PMID:Reversible pulmonary oxygen toxicity in the primate. 21 38

1. The membrane-bound succinoxidase of Escherichia coli was fractionated with deoxycholate into three soluble components, viz. succinate dehydrogenase.cytochrome b1 complex, cytochrome oxidase complex, and a factor identified as a phospholipid-containing component. 2. The dehydrogenase and cytochrome oxidase complexes were partially purified by filtration on Amicon membranes, Sepharose 4B chromatography, and sucrose gradient centrifugation. 3. Reconstitution of membranous succinoxidase, which catalyzes the oxidation of succinate by molecular oxygen by an integrated CN(-)-sensitive pathway, was achieved by mixing the soluble succinate dehydrogenase.cytochrome b1 complex with the soluble cytochrome oxidase complex in the presence of deoxycholate and then removing the detergent by gel filtration on Sephadex G-75. The phospholipid-containing factor stimulated the formation of succinoxidase by about 100% over that observed with the two complexes. 4. Isopycnic sucrose gradient centrifugation of succinate dehydrogenase.cytochrome b1 complex, cytochrome oxidase, and the reconstituted succinoxidase gave buoyant densities (p value) as 1.167, 1.229, and 1.194, respectively. 5. Electron microscopic evidence is presented for the vesicular nature of the reconstituted succinoxidase.
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PMID:Reconstitution of escherichia coli succinoxidase from soluble components. 21 41

Cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1) has been resolved into a pair of complexes of unequal molecular weight. The larger complex (electron transfer complex) contains exclusively the oxidation-reduction proteins characteristic of cytochrome oxidase; the smaller complex (ion transfer complex) shows exclusively the capability for cation-dependent induction of the fluorescence of 8-anilino-1-naphthalenesulfonic acid--a capability demonstrable in preparations of cytochrome oxidase. The duplex nature of cytochrome oxidase has important implications for the mechanism of energy coupling.
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PMID:Resolution of cytochrome oxidase into two component complexes. 21


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