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)

An active respiratory chain system was demonstrated in sonically treated mycelium of Streptomyces antibioticus, the producer of antimycin A. The respiratory electron transfer from substrate to oxygen proceeded successively through flavoprotein(s), b-, c-, and a-type cytochromes, and terminated with the cyanide-sensitive cytochrome oxidase. The cytochrome composition of the culture was not affected by the age of the mycelium, the intensity of antimycin A production, or differences in the media. Slater factor, coenzyme Q, and vitamin K were not interposed as hydrogen carriers in the respiratory chain between flavoproteins and cytochromes. The oxidation of reduced nicotinamide adenine dinucleotide and succinate was unaffected by antimycin A. Evidence is presented in support of the absence of the antimycin A-sensitive site from the electron transport system of S. antibioticus.
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PMID:Respiratory chain of antimycin A-producing Streptomyces antibioticus. 429 78

Toyopearl media for gel filtration tend to adsorb proteins at high ionic strength, presumably by hydrogen bonding. This is used in the technique proposed here for resolution of crude protein mixtures and initial purification of their components. Proteins can be selectively adsorbed on a column of Toyopearl at high ammonium sulfate concentration and then eluted by decreasing the salt concentration. This single-step procedure can replace the usual salt fractionation of protein mixtures, which is demonstrated with yeast cytochrome oxidase.
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PMID:Adsorption chromatography on Toyopearl: a single-step alternative to salt fractionation of protein mixtures. 609 56

Oxidative titration of reduced cytochrome oxidase (cytochrome c oxidase; ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in the presence of carbon monoxide and sulfide, at potentials greater than +500 mV (vs. the neutral hydrogen electrode), have failed to produce new copper signals in the electron paramagnetic resonance spectrum of this enzyme. This observation implies that once of the copper centers in cytochrome oxidase remains Cu(I) under strongly oxidizing conditions. The rationalization of this fact, and the possible explanation of a great accumulation of spectroscopic data, is that cytochrome a3 may be a two-electron redox center, with stable Fe(IV), Fe(III), and Fe(II) states during its redox cycle. This oxidase model does not require an antiferromagnetic coupling scheme, in contrast to currently prevalent models.
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PMID:Cytochrome oxidase: an alternative model. 624 5

A hypothetical three-dimensional model of the cytochrome c peroxidase . tuna cytochrome c complex is presented. The model is based on known x-ray structures and supported by chemical modification and kinetic data. Cytochrome c peroxidase contains a ring of aspartate residues with a spatial distribution on the molecular surface that is complementary to the distribution of highly conserved lysines surrounding the exposed edge of the cytochrome c heme crevice, namely lysines 13, 27, 72, 86, and 87. These lysines are known to play a functional role in the reaction with cytochrome c peroxidase, cytochrome oxidase, cytochrome c1, and cytochrome b5. A hypothetical model of the complex was constructed with the aid of a computer-graphics display system by visually optimizing hydrogen bonding interactions between complementary charged groups. The two hemes in the resulting model are parallel with an edge separation of 16.5 A. In addition, a system of inter- and intramolecular pi-pi and hydrogen bonding interactions forms a bridge between the hemes and suggests a mechanism of electron transfer.
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PMID:A hypothetical model of the cytochrome c peroxidase . cytochrome c electron transfer complex. 625 70

Oxidized cytochrome c oxidase can bind hydrogen peroxide, as evidenced by changes in its spectrum and its ability to use hydrogen peroxide as an electron acceptor in cytochrome c oxidation. The affinity of the oxidized enzyme for hydrogen peroxide is high, with a Kd of less than 10 microM, and the binding is inhibited by ligands of cytochrome a3. Oxidized cytochrome c oxidase, in submitochondrial particles or solubilized in several ionic and nonionic detergents, binds peroxide with comparable affinities. The size of the spectral shift observed upon peroxide binding depends on the pH of the solution and differs in extinction coefficient between preparations, but all preparations tested appeared to bind peroxide. The differences in the magnitude of the spectral shift upon peroxide binding to different preparations suggest that oxidized cytochrome c oxidase as prepared may be made up of more than one species and that the proportion of the species which binds peroxide varies with the preparation. These studies of the binding of peroxide clarify the mechanism by which cytochrome c oxidase catalyzes the reduction of oxygen to water without the formation of free-radical intermediates.
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PMID:Cytochrome c oxidase binding of hydrogen peroxide. 628 5

I have found that mammalian cytochrome oxidase catalyzes the peroxidatic oxidation of ferrocytochrome c under strictly anaerobic conditions. An apparent Km value for ferrocytochrome c was 2 microM, and a second order rate constant, estimated as an extrapolated value, was 1.4 X 10(6) M-1 s-1 at pH 7.4 at 25 degrees C. These values were quite similar to the corresponding values of 6.4 microM and 1.9 X 10(6) M-1 s-1 determined for the intrinsic oxidase activity. The rate of the peroxidatic oxidation showed a hyperbolic dependence on the concentration of hydrogen peroxide, and the apparent Km value ws 0.18 mM. Cyanide and azide at 0.1 mM inhibited the peroxidase activity by 100 and 98%, respectively, whereas, under carbon monoxide at 750 mm Hg, 10% of the activity still remained. Under air, cytochrome oxidase acted simultaneously as oxidase and peroxidase.
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PMID:The cytochrome c peroxidase activity of cytochrome oxidase. 628 8

The heme a formyl group of cytochrome a in cytochrome oxidase appears to be involved in a hydrogen-bond interaction with a proton donor associated with the polypeptide backbone [Callahan, P.M., & Babcock, G.T. (1983) Biochemistry 22, 452-461]. Resonance Raman and optical absorption spectroscopies have been applied to the beef heart and Thermus thermophilus proteins and to heme a and copper porphyrin a models in order to assess the spectroscopic manifestations and the energetics of the hydrogen-bond interaction. We find a linear relationship between optical absorption red shift and carbonyl vibrational frequency decrease for a series of hydrogen-bonded model complexes; the magnitude of both changes increases as the hydrogen-bond strength increases. Comparison of the model compound data with analogous data for the proteins indicates that the strength of the formyl hydrogen bond in situ increases by 2-2.5 kcal/mol upon reduction of ferric cytochrome a. The selective stabilization of reduced cytochrome a by the stronger hydrogen bond is expected to increase the redox potential of this center; the energy made available as the hydrogen bond strengthens during reduction may be used to drive redox-coupled events in the protein. Thus, the linkage between cytochrome a redox state and chromophore/protein interaction energy provides a mechanism by which electron-transfer events and protein structure are coupled. Two models, which incorporate this linkage into a redox-driven proton pump centered at cytochrome a in cytochrome oxidase, are presented.
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PMID:Redox-linked hydrogen bond strength changes in cytochrome a: implications for a cytochrome oxidase proton pump. 630 99

Reduction and reoxidation of beef heart cytochrome oxidase, under conditions that ensure the strict absence of hydrogen peroxide, produce a fully oxidized form of the enzyme that has the Soret band at 420 nm, as opposed to the 428 nm band normally associated with the pulsed or oxygenated enzyme. The 420 nm form shows the enhancement of catalytic activity associated with the pulsed enzyme. Addition of hydrogen peroxide to the 420 nm form gives rise to the 428 nm band of the oxygenated enzyme, thereby clearly establishing that the 428 nm form is a peroxide derivative of the fully oxidized enzyme. Previous data from other groups are re-evaluated in the light of our experiments.
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PMID:The identity of pulsed cytochrome oxidase. 632 57

A paramagnetic intermediate with an unusual e.p.r. spectrum is formed when fully reduced cytochrome c oxidase is allowed to react with dioxygen at 173 K. The effect on the e.p.r. spectrum of using dioxygen enriched in 17O was investigated. These experiments show that an oxygen atom derived from dioxygen is bound to Cu2+ in the intermediate. The e.p.r. parameters can be explained in terms of a weak antiferromagnetic interaction (J approximately equal to 10 cm-1) between Cu2+B and cytochrome a3 in the low-spin ferryl ion state. It is suggested that an OH- ion bound to Cu2+B is hydrogen bonded to the oxygen atom of the ferryl ion in cytochrome a3.
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PMID:The structure of the paramagnetic oxygen intermediate in the cytochrome c oxidase reaction. 632 62

Even 70 years ago Gram-negative coccobacilli had been recognized in vaginal discharge and were cultured 30 years ago. The need to have blood in agar medium for cultivation suggested that the organisms might be a Haemophilus species. Later, however, growth characteristics and other features resulted in their being placed in the genus Corynebacterium, before it was realized that this was inappropriate and they were transferred to a new genus and species Gardnerella vaginalis. The organisms are Gram-variable, non-sporing, non-flagellate, non-motile coccobacilli of average size 0.4 X 1-1.5 microns. The cell wall is laminated and some strains possess pili. G. vaginalis is fermentative and dextrose, fructose, galactose, glucose, maltose, mannose, ribose and starch are most likely to be metabolized. However, published patterns of the sugars fermented vary widely and most workers do not rely on such tests as a means of identification. Of many other features exhibited by G. vaginalis, the following are outstanding: it does not produce catalase, cytochrome oxidase, hydrogen sulphide, indole, or urease. Nor does it degrade aesculin, liquefy gelatin, reduce nitrate, or decarboxylate arginine, lysine or ornithine. On the other hand, it is sensitive to hydrogen peroxide, often causes beta-haemolysis and usually hydrolyses hippurate and starch. G. vaginalis is serologically heterogeneous and causes haemagglutination which is mannose resistant. It is resistant to several antibiotics, including amphotericin, colistin, nalidixic acid and gentamicin, which may be incorporated in selective media.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The bacteriology of Gardnerella vaginalis. 639 9


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