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

---

Query: EC:1.9.3.1 (cytochrome oxidase)
8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of antimycin on (i) the respiratory activity of the KCN-insensitive pathway of mitochondria of Neurospora grown on chloramphenicol (chloramphenicol-grown) with durohydroquinone and succinate or NADH as substrate, (ii) the electron transfer from the b-type cytochromes to ubiquinone with durohydroquinone as electron donor as well as (iii) the electron transfer from the b-type cytochromes to duroquinone with succinate as electron donor in chloramphenicol-grown Neurospora and beef heart submitochondrial particles was studied. All experiments were performed in the uncoupled state. 1. The respiratory chain of chloramphenicol-grown Neurospora mitochondria branches at ubiquinone into two pathways. Besides the cytochrome oxidase-dependent pathway, a KCN-insensitive branch equiped with a salicylhydroxamate-sensitive oxidase exists. Durohydroquinone, succinate or NADH are oxidized via both pathways. The durohydroquinone oxidation via the KCN-insensitive pathway is inhibited by antimycin, wheras the succinate or NADH oxidation is not. The titer for ful inhibition is one mol antimycin per mol cytochrome b-563 or cytochrome b-557. 2. The electron transfer from durohydroquinone to ubiquinone, which takes place in the KCN-inhibited state, does not occur in the antimycin-inhibited state. 3. The reduction of duroquinone by succinate in the presence of KCN is inhibited by antimycin. The titer for full inhibition is one mol antimycin per mol cytochrome b-566 or cytochrome b-562 for beef heart (or cytochrome b-563 or cytochrome b-557 for Neurospora). 4. When electron transfer from the b-type cytochromes to cytochrome C1, ubiquinone and duroquinone is inhibited by antimycin, the hemes of cytochrome b-566 and cytochrome b-562 (or cytochrome b-563 and cytochrome b-557) are in the reduced state. 5. The experimental results suggest that the two b-type cytochromes form a binary complex the electron transferring activity of which is inhibited by antimycin, the titer for full inhibition being one mol of antimycin per mol of complex. The electron transfer from the b-type cytochromes to ubiquinone is inhibited in a non-linear fashion.
...
PMID:Inhibition of electron transfer from ferrocytochrome b to ubiquinone, cytochrome c1 and duroquinone by antimycin. 16 67

The electron-transfer reaction between azurin and cytochrome c1 isolated from Pseudomonas aeruginosa was investigated by rapid-reaction techniques. Temperture-jump studies clearly reveal two chemical relaxations, the amplitudes of which have ikentical spectral distributions, but relaxation times show different dependencies on reactant concentrations. Stopped experiments also showed complex kinetics. A model is proposed which is consistent with the kinetic and equilibrium data obtained. The central feature of this model is the proposal that two intercenvertible forms of reduced azurin exist in solution, only one of which si able to participate directly in the electron-transfer reaction with cytochrome c-551. Support for the hypothesis that two forms of reduced azurin exist is derived from studies on the electron-transfer reaction between azurin and Pseudomonas cytochrome oxidase. The possible physiological significance of such a situation is discussed.
...
PMID:Electron transfer between azurin and cytochrone c-551 from Pseudomonas aeruginosa. 16 67

In stopped-flow experiments in which oxidized cytochrome c oxidase was mixed with ferrocytochrome c in the presence of a range of oxygen concentrations and in the absence and presence of cyanide, a fast phase, reflecting a rapid approach to an equilibrium, was observed. Within this phase, one or two molecules of ferrocytochrome were oxidized per haem group of cytochrome a, depending on the concentration of ferrocytochrome c used. The reasons for this are discussed in terms of a mechanism in which all electrons enter through cytochrome a, which, in turn, is in rapid equilibrium with a second site, identified with 'visible' copper (830 nm-absorbing) Cud (Beinert et al., 1971). The value of the bimolecular rate constant for the reaction between cytochromes c2+ and a3+ was between 10(6) and 10(7) M(-1)-S(-1); some variability from preparation to preparation was observed. At high ferrocytochrome c concentrations, the initial reaction of cytochrome c2+ with cytochrome a3+ could be isolated from the reaction involving the 'visible' copper and the stoicheiometry was found to approach one molecule of cytochrome c2+ oxidized for each molecule of cytochrome a3+ reduced. At low ferrocytochrome c concentrations, however, both sites (i.e. cytochrome a and Cud) were reduced simultaneously and the stoicheiometry of the initial reaction was closer to two molecules of cytochrome c2+ oxidized per molecule of cytochrome a reduced. The bleaching of the 830 nm band lagged behind or was simultaneous with the formation of the 605 nm band and does not depend on the cytochrome c concentration, whereas the extinction at the steady-state does. The time-course of the return of the 830 nm-absorbing species is much faster than the bleaching of the 605 nm-absorbing component, and parallels that of the turnover phase of cytochrome c2+ oxidation. Additions of cyanide to the oxidase preparations had no effect on the observed stoicheiometry or kinetics of the reduction of cytochrome a and 'visible' copper, but inhibited electron transfer to the other two sites, cytochrome a3 and the undetectable copper, Cuu.
...
PMID:Kinetic studies on the reaction between cytochrome c oxidase and ferrocytochrome c. 16 79

1) Cells of Saccharomyces cerevisiae have been analysed by single and double-bean spectroscopy. Evidence is given for two components of cytochrome c oxidase in the alpha-region of their absorption spectrum. A rapidly reduceable component with a maximum at 600 nm and a slowly reduceable component with a maximum at 604 nm contribute about equal amounts to the total alpha-absorption of cytochrome c oxidase. 2) The component absorbing at 600 nm was identified as the high-potential component with a redox potential of 340 - 355mV, and the 604-nm component as the low-potential component of cytochrome c oxidase with redox potential of 180 - 190 mV. 3) Both components can be characterized by analysing the reduction kinetics in the presence of carbon monoxide. In the presence of saturating concentrations of carbon monoxide, an oxygen pulse leads to a rapid oxidation and subsequent reduction of cytochrome c oxidase, but the rapid reduction phase at 600 nm completely disappears, demonstrating its identity with cytochrome a3, which, being liganded by carbon monoxide in its reduced state, cannot react any more. The component which becomes oxidized and later reduced in the presence of carbon monoxide -- by definition cytochrome a -- has an absorption maximum at 604 nm. 4) The total extinction change at 604 nm in the presence of carbon monoxide is nearly as high as in its absence, but the reduction occurs in two phases and only the second phase, which contributes 50 - 60% to the total absorbance, corresponds in redox potential and kinetic properties to cytochrome a. Because the redox potential of the first reduction phase is very close to that of the low-potential copper atom of cytochrome c oxidase, it is concluded that the apparent increase in the extinction coefficient of cytochrome a in the presence of carbon monoxide is the result of a strong interaction between the ligand fields of cytochrome a and copper, induced by the binding of carbon monoxide to reduced cytochrome a3.
...
PMID:Identification of cytochrome a and a3 in yeast cells. 17 24

The effects of hydroxycobalamin on inhibition of cytochrome c oxidase by cyanida in isolated intact mitochondria were studied. No effect of hydroxycobalamin (HCo) and cyanocobalamin (CNCo) was observed on normal mitochondria. When mitochondria inhibited by cyanida were treated with HCo the respiration with ADP, the respiration after ADP and respiratory coefficient (RC) were increased. No effect was observed with CNCo. Difference spectra of the effect of HCo on the inhibition of cytochrome c oxidase by cyanida and azide in isolated intact mitochondria were recorded using a split beam spectrophotometer. The results presented herein suggest that HCo reverses the cyanide inhibition because part of cytochrome a3 is free from cyanide as a consequence of dissociation of the complex, resulting in CNCo formation. If this reaction continues to occur together with a probable by pass between cytochrome a and oxygen throught the HCo (which was not transformed in CNCo), oxygen consumption and most of the respiratory chain will be maitened in the active state.
...
PMID:Effect of hydroxycobalamin on the inhibition of cytochrome c oxidase by cyanide. I - In intact mitochondria. 17 99

The basic protein protamine is found to be a potent inhibitor of mitochondrial cytochrome c oxidase, while the oxidase activity of the "inside out" submitochondrial particles is only slightly affected by this polycation. The site of inhibition of mitochondrial respiration by protamine is localized between cytochromes c and a, protamine combining with cytochrome oxidase competitively to cytochrome, c, Ki=2,5 x 10(-6) M. The data obtained suggest that it is the outer side of the mitochondrial membrane where oxidation of cytochrome c by cytochrome a occurs.
...
PMID:[Protamine as a specific inhibitor of electron transport between cytochromes c and a on the outer surface of the mitochondrial membrane]. 17 21

1. Beef heart mitochondria have a cytochrome c1:c:aa3 ratio of 0.65:1.0:1.0 as isolated; Keilin-Hartree submitochondrial particles ahve a ratio of 0.65:0.4:1.0. More than 50% of the submitochondrial particle membrane is in the 'inverted' configuration, shielding the catalytically active cytochrome c. The 'endogenous' cytochrome c of particles turns over at a maximal rate between 450 and 550 s-1 during the oxidation of succinate or ascorbate plus TMPD; the maximal turnover rate for cytochrome c in mitochondria is 300-400 s-1, at 28 degrees-30 degrees C, pH 7.4. 2. Ascorbate plus N,N,N',N'-tetramethyl-p-phenylene diamine added to antimycin-treated particles induces anomalous absorption increases between 555 and 565 nm during the aerobic steady state, which disappear upon anaerobiosis; succinate addition abolishes this cycle and permits the partial resolution of cytochrome c1 and cytochrome c steady states at 552.5-547 nm and 550-556.5 nm, respectively. 3. Cytochrome c1 is rather more reduced than cytochrome c during the oxidation of succinate and of ascorbate + N,N,N',N'-tetramethyl-p-phenylene diamine in both mitochondria and submitochondrial particles; a near equilibrium condition exists between cytochromes c1 and c in the aerobic steady state, with a rate constant for the c1 leads to c reduction step greater than 10(3) s-1. 4. The greater apparent response of the c/aa3 electron transfer step to salts, the hyperbolic inhibition of succinate oxidation by azide and cyanide, and the kinetic behaviour of the succinate-cytochrome c reductase system, are all explicable in terms of a near-equilibrium condition prevailing at the c1/c step. Endogenous cytochrome c of mitochondria and submitochondrial particles is apparently largely bound to cytochrome aa3 units in situ. Cytochrome c1 can either reduce the cytochrome c-cytochrome aa3 complex directly, or requires only a small extra amount of cytochrome c to carry the full electron transfer flux.
...
PMID:Catalytic activity of cytochromes c and c1 in mitochondria and submitochondrial particles. 17 75

The ratio between the nitrite reductase and cytochrome oxidase activities of Pseudomonas aeruginosa nitrite reductase [EC 1.9.3.2.] varies with kind of C-type cytochrome used as the electron donor. Withe cytochrome c-548, 554 (Micrococcus sp.), the nitrite reductase activity is greater than the cytochrome oxidase activity, while the former is smaller than the latter with cytochrome c-554 (Navicula pelliculosa). The aerobic oxidation catalyzed by this enzyme of denitrifying bacterial ferrocytochrome c is greatly accelerated on addition of nitrite, while that of the algal ferrocytochrome c is not affected or is even depressed by the salt. An accelerative effect of nitrite is generally observed with many kinds of C-type cytochromes which react with the enzyme very or fairly rapidly. The difference in the ratio of the two activities of the enzyme seems to arise according to whether or not nitrite affects the interaction of C-type cytochrome with the enzyme.
...
PMID:Change in the ratio of cytochrome oxidase activity to nitrite reductase activity of Pseudomonas aeruginosa nitrite reductase with the kind of C-type cytochrome used as an electron donor. 17 46

Rat heart and liver cytochrome concentrations were determined after three hypoxic conditions (atmospheric pressure 50.5 kPa, 40.8 kPa and 38.0 kPa) lasting one week and two weeks. The heart showed clear hypertrophy which was 38% in most severe hypoxia (38 kPa, 2 weeks). A small decline in the liver weight to body weight ratio was observed, this decrease being 21% in the most severe case. During the hypoxic periods the mitochondrial cytochrome concentration decreased. This phenomenon was more obvious when the degree of hypoxia was increased and more pronounced after 2 weeks than one week. The heart and liver showed quite similar patterns in this respect. In most severe hypoxia the decreases in the liver were 29% for cytochrome aa3, 30% for cytochrome b, 20% for cytochrome c and 15% for cytochrome c1, with the concentrations expressed on mitochondrial protein basis. The corresponding values in the heart were 31%, 43%, 28%, and 22%. It can be concluded that in mammals the mitochondrial cytochrome content probably varies according to the amount of oxygen available.
...
PMID:Mitochondrial cytochrome concentrations in rat heart and liver as a consequence of different hypoxic periods. 17 79

A model is proposed for the active center of cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in which cytochrome a is a low-spin ferrihemoprotein and cytochrome a3 is a high-spin ferrihemoprotein antiferromagnetically coupled to one of the two Cu2+ ions present in the enzyme. It is further proposed that reduction is accompanied by a conformational change in the enzyme thus exposing the sixth coordination site of cytochrome a3 to ligands. With this model it is possible to account for a variety of outstanding observations including the results of magnetic circular dichroism, Mossbauer, and electron paramagnetic resonance spectroscopies, as well as magnetic susceptibility measurements.
...
PMID:A model for cytochrome oxidase. 18 47


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---