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)

Activities of succinate dehydrogenase, succinate- and NAD-H-cytochrome c--reductases, and cytochrome c--oxidase was compared in 1 g tissue homogenate and homogenate fractions made from 1 g brain tissue using various solutions. Fractionation resulted in the increased activities of NADH- and succinate cytochrome reductases, and in the loss of succinate dehydrogenase activity, cytochrome oxidase was less influenced. These phenomena are regarded as signs of the interrelation between mitochondria and other constituents of brain cell within homogenates. Maximal quantity of mitochondria isolated from homogenates is no more than 20% of all the mitochondrial homogenates (according enzyme data). The electronogram of the brain mitochondrial preparation isolated in the Krebs--Ringer solution without glucose pointed out to a high homogeneity of mitochondria in the residue.
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PMID:[Enzyme, electron microscopic and polarographic characteristics of isolated rat brain mitochondria. III. Quantitative assessment of their distribution in fractions of the homogenate]. 18 80

1. Cells of the hydrogen bacterium Alcaligenes eutrophus are broken by gentle lysis using lysozyme treatment in hypertonic sucrose followed by osmotic shock. By this method, 93% of the in vivo activity of the H2 oxidase is recovered and the ATPase remains particle bound. In contrast, cell disruption in a French pressure cell diminishes the in vivo activity of the H2 oxidase by 50% and solubilizes the bulk of the ATPase. 2. The bacterium contains a periplasmic cytochrome c with bands at 418, 521 and 550 nm (difference spectrum). In addition to cytochrome aa3, b-560, c-553 and o, low temperature difference spectra of membranes show the presence of two further cytochromes (shoulders at 551 and 553 nm). 3. The unsupplemented membrane fraction catalyses the oxidation of hydrogen, NADH, NADPH, succinate, formate and endogenous substrate (NAD linked) at rates 2--3-fold higher than membranes obtained from cells disrupted in a French pressure cell. With the exception of the H2 oxidase all oxidase activities in lysozyme membranes are sensitive to carbonylcyanide m-chlorophenylhydrazone (20-100% stimulation of oxygen uptake). 4. The cytoplasmic fraction contains a B-type cytochrome with absorption maxima at 436 and 560 nm, capable of combining with CO; it contains non-covalently bound protohaem. In alkaline solutions a spectral transition to the haemochrome type with bands at 423, 526 and 556 nm occurs. The addition of NADH to an aerobic suspension of this cytochrome elicits new absorption maxima at 418, 545 and 577 nm (difference spectrum), which are believed to represent an oxygenated form of the reduced cytochrome.
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PMID:Respiratory components and oxidase activities in Alcaligenes eutrophus. 18 46

The production of the soluble cytochrome oxidase/nitrite reductase in the bacterium Pseudomonas aeruginosa is favoured by anaerobic conditions and the presence of KNO3(20g/l) in the culture medium. Of three methods commonly used for the disruption of bacterial suspensions (ultrasonication, liquid-shear homogenization and glass-bead grinding), sonication proved the most efficient in releasing the Pseudomonas cytochrome oxidase. A polarographic assay of Pseudomonas cytochrome oxidase activity with sodium ascorbate as substrate and NNN'N'-tetramethyl-p-phenylenediamine dihydrochloride as electron mediator is described. A purification procedure was developed which can be used on the small scale (40-litre cultures) or the large scale (400-litre cultures) and provides high yields of three respiratory-chain proteins, Pseudomonas cytochrome oxidase, cytochrome c551 and azurin, in a pure state. A typical preparation of 250g of Ps.aeruginosa cell paste yielded 180mg of Pseudomonas cytochrome oxidase, 81 mg of Pseudomonas cytochrome c551 and 275mg of Pseudomonas azurin.
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PMID:A purification procedure for the soluble cytochrome oxidase and some other respiratory proteins from Pseudomonas aeruginosa. 18 50

The kinetics of the electron-transfer process which occurs between ferrocytochrome c and partially reduced mammalian cytochrome oxidase were studied by the rapid spectrophotometric techniques of stopped flow and temperature jump. Stopped-flow experiments showed initial very fast extinction changes at 605 nm and at 563 nm, indicating the simultaneous reduction of cytochrome a and oxidation of ferrocytochrome c. During this 'burst' phase, say the first 50 ms after mixing, it was invariably found that more cytochrome c had been oxidized than cytochrome a had been reduced. This discrepancy in electron equivalents may be accounted for by the rapid reduction of another redox site in the enzyme, possibly that associated with the extinction changes observed at 830 nm. During the incubation period in which the partially reduced oxidase was prepared, the rate of reduction of cytochrome a by ferrocytochrome c, at constant reactant concentrations, decreased with time. Temperature-jump experiments showed the presence of two relaxation processes. The faster of the two phases was assigned to the electron-transfer reaction between cytochrome c and cytochrome a. A study of the concentration-dependence of the reciprocal relaxation time for this phase yielded a rate constant of 9 X 10(6)M-1-s-1 for the electron transfer from cytochrome c to cytochrome a, and a value of 8.5 X 10(6)M-1-s-1 for the reverse reaction. The equilibrium constant for the electron-transfer reaction is therefore close to unity. The slower phase has been interpreted as signalling the transfer of electrons between cytochrome a and another redox site within the oxidase molecule.
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PMID:Studies on partially reduced mammalian cytochrome oxidase reactions with ferrocytochrome c. 18 26

1. The spectral shifts induced on the binding of H2S to ferric cytochrome aa3 are similar to those induced by cyanide, reflecting a possible high- to low-spin state change in the a3 haem. Opposite shifts are seen with either formate or low azide concentrations, while high azide concentrations reverse the change induced at lower concentrations. The unusually high Soret band in the half-reduced sulphide-inhibited species (a2+a33+H2S) results from the superposition of cytochrome a2+ and cytochrome a33+H2S peaks. 2. The difference spectra in the visible region for cytochrome a2+ minus cytochrome a3+ obtained with four inhibitors (cytochrome a2+ a3+I minus minus a3+a33+I)are similar, except that azide and sulphide induce blue shifts of the alpha-peak. The trough in the Soret region for the azide complex is much deeper than that for the other complexes, suggesting changes in the cytochrome a33+HN3 centre on reduction of cytochrome a. 3. The "oxygenated" and "high-energy" forms of cytochrome aa3 both involve spectral changes at the a3 haem similar to the changes induced by cyanide and sulphide. The spectrum of partially reduced cytochrome aa3 in the presence of reductant and oxygen indicates the steady-state occurrence of appreciable levels of low-spin (oxygenated) cytochrome aa3. These may be important for energy conservation during the action of cytochrome aa3 in the intact mitochondrial membrane.
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PMID:Ligand-induced spectral changes in cytochrome c oxidase and their possible significance. 18 15

The 18 extranuclear mutants of Neurospora crassa, without exception, have abnormal mitochondrial respiratory systems. On the basis of genetic, phenotypic and physiological criteria, these mutants are divided into four groups: 1) the cytochrome aa3 and b deficient "poky" variants that are defective in mitochondrial ribosomes assembly, 2) the cytochrome aa3 deficient mutants, [mi-3] and [exn-5], that appear to have genetic lesions affecting a component of a regulatory system controlling cytochrome aa3 synthesis, 3) the cytochrome aa3 and b deficient "stopper" mutants with physiological lesions that probably affect mitochondrial protein synthesis, and 4) cni-3, a mutant that is constitutive for an inducible mitochondrial cyanide-insensitive oxidase in spite of having a normal cytochrome mediated electron-transport system. It is proposed that the mitochondrial genophore not only codes for cellular components that are essential for the formation of the mitochondrial protein synthesizing apparatus, but also for components of a regulatory system that coordinates the expression of nuclear and mitochondrial genes during the biogenesis of the mitochondrial electorn-transport system.
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PMID:The function of mitochondrial genes in Neurospora crassa. 18 90

Magnetic circular dichroism (MCD) spectra have been recorded for beef heart cytochrome oxidase and a number of its inhibitor complexes. The resting enzyme exhibits a derivate shape Faraday C term in the Soret region, characteristic of low spin ferric heme, which accounts for 50% of the total oxidase heme a. The remaining heme a (50%) is assigned to the high spin state. MCD temperature studies, comparison with the MCD spectra of heme a-imidazole model compounds, and ligand binding (cyanide, formate) studies are consistent with these spin state assignments in the oxidized enzyme. Furthermore, the ligand binding properties and correlations between optical and MCD parameters indicate that in the resting enzyme the low spin heme a is due solely to cytochrome a3+ and the high spin heme a to cytochrome a33+. The Soret MCD of the reduced protein is interpreted as th sum of two MCD curves: an intense, asymmetric MCD band very similar to that exhibited by deoxymyoglobin which we assign to paramagnetic high spin cytochrome a3(2+) and a weaker, more symmetric MCD contribution, which is attributed to diamagnetic low spin cytochrome a2+. Temperature studies of the Soret MCD intensity support this proposed spin state heterogeneity. Ligand binding (CO, CN-) to the reduced protein eliminates the intense MCD associated with high spin cytochrome a3(2+); however, the band associated with cytochrome a2+ is observed under these conditions as well as in a number of inhibitor complexes (cyanide, formate, sulfide, azide) of the partially reduced protein. The MCD spectra of oxidized, reduced, and inhibitor-complexed cytochrome oxidase show no evidence for heme-heme interaction via spectral parameters. This conclusion is used in conjunction with the fact that ferric, high spin heme exhibits weak MCD intensity to calculate the MCD spectra for the individual cytochromes of the oxidase as well as the spectra for some inhibitor complexes of cytochrome a3. The results are most simply interpreted using the model we have recently proposed to account for the electronic and magnetic properties of cytochrome (Palmer, G., Babcock, F.T., and Vcikery, L.E. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 2206-2210).
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PMID:Electronic state of heme in cytochrome oxidase. I. Magnetic circular dichroism of the isolated enzyme and its derivatives. 18 99

E.p.r.(electron-paramagnetic-resonance) spectra of the ferricytochromes were studied in normal and 'nickel-plated' pigeon heart mitochondria and pigeon heart submitochondrial particles. NiCL2 added to either mitochondria or particles was bound completely to the membranes, but none was transported across the vesicles. Hence, any perturbations of the haem e.p.r. spectra by Ni(II) should occur only for those cytochromes in close proximity to the exterior surface. Whenever Ni(II) can approach to within 1 nm of cytochrome haem. the consequent acceleration of the haem e.p.r. relaxation kinetics should elicit dipolar line broadening. Relaxation acceleration should also increase the incident power level required to saturate the haem e.p.r. signal. In pigeon heart mitochondria, at least three e.p.r. resonances, attributable in part to cytochromes c1, bK and br, are observed at gz=3.3 resonance. In these submitochondrial particles, the peak at gz=3.5 is missing, and the resonance at gz=3.6 resolves into two components, neither of which is sensitive to added Ni(ii). Addition of free haemin (ferric, a paramagnetic anion) to intact mitochondria elicits the same e.p.r. signal changes as does a preparation of submitochondrial particles. Saturation curves for cytochrome oxidase obtained for e.p.r. spectra of the high-spin form (g = 6) and the low-spin form (gz=3.1) also reveal no effect of Ni(II) on the haem e.p.r. relaxation in either mitochondria or inverted submitochondrial particles. Further, Ni(II) fails to alter the spectra or saturation properties of cytochrome c in either mitochondria or submitochondrial particles therefrom. Only with a 50-fold molar excess of Ni(II) can one accelerate the e.p.r. relaxation of cytochrome c in aqueous solution, although other more subtle types of magnetic interactions may occur between the cytochrome and either Ni(II) or ferricyanide. Addition of haemin to mitochondria likewise failed to alter the e.p.r. characteristics of either cytochrome c or cytochrome oxidase. The present observations strongly suggest that cytochromes bK, br and c1 reside on the exterior surface of the inner mitochondrial membrane. On the other hand, we find no positive evidence for the location of cytochrome c or cytochrome oxidase haem groups within 1 nm of either membrane surface. Because of possible shielding effects from the protein moieties, however, we cannot unequivocally assign the location of the haem groups to the membrane interior. The present results are not inconsistent with the observations of other investigators who used different techniques. However, it is clear that any model of energy coupling in mitochondrial oxidative phosphorylation must account for the positioning of all the b-c cytochrome haem groups on the outside.
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PMID:Intramitochondrial positions of cytochrome haem groups determined by dipolar interactions with paramagnetic cations. 18 58

The effect of CO on the optical absorbance spectrum of partially reduced cytochrome c oxidase has been studied. The changes at 432 and 590 nm suggest that the cytochrome alpha2/3+ - CO compound is formed preferentially and that concomitantly a second electron is taken up by the enzyme. From the CO-induced changes at 830 nm it is concluded that in the partially reduced enzyme addition of CO causes reoxidation of the copper component of cytochrome c oxidase. Addition of CO to partially reduced enzyme (2 electrons per 4 metal ions) also brings about a decrease in the intensities of electron paramagnetic resonance signals of high-spin heme iron near g = 6 and of the low-spin heme at g = 2.6. Concomitantly both the low-spin heme a signal at g = 3 and the copper signal at g = 2 increase in intensity. These results demonstrate that formation of the reduced diamagnetic cytochrome a3 - CO compound is accompanied by reoxidation of both the copper component detectable by electron paramagnetic resonance and possibly also by cytochrome a.
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PMID:The binding of carbon monoxide to cytochrome c oxidase. 19 7

In 175 dogs myocardial infarction was produced by high ligation of descending branch of left coronary artery. At various intervals after the intervention (1, 3, 5, 10, 30, 180 days), the activities and levels of NAD, NADH, FAD, riboflavin, cytochrome C, myoglobin, some NAD-dependent Krebs cycle enzymes, and mitochondrial succinate dehydrogenase and cytochrome oxidase were determined in the infarcted zone. It was found that in the infarcted zone there occurred substantial disturbances of various links constituting the tissue oxidative chain, in the stages of substrate dehydrogenation, electron transport to oxygen molecule, and myocardial oxygen uptake. The greatest disturbances took place in the systems of NAD and NAD-dependent enzymes, whereas the succinate oxidation system sustained substantially lesser damage. The decrease inlevels of flavonoids, which was likewise observed, participated also in the mechanism inhibiting succinate dehydrogenase. The cytochrome system activity was limited by the level of cytochrome C, whose deep decrease persisted considerably long in the infarcted zone. A certain role in disturbances of oxidative processes may have been played by the decreased concentration of myoglobin, an important myocardial reservoir of oxygen.
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PMID:Some myocardial factors of biological oxidation in experimental myocardial infarction. 19 79


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