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 ultrastructural localization of the activities of two enzyme systems in the culture forms of Leishmania donovani was shown by means of the diaminobenzidine techniques. The consistent deposition of electron dense reaction product of DAB oxidation without H2O2 in the kinetoplast and mitochondrial cristae and membranes was taken as evidence of the presence of cytochrome oxidase activity and cytochrome c. In the presence of H2O2, a more intense DAB oxidation was attributed to the activity of a peroxidase, possibly cytochrome c peroxidase. Mitochondrial and kinetoplast reactions to DAB were completely inhibited by KCN, methanol-nitroprusside, and by heating to 50 degrees C for 10 min. On the other hand, no inhibitory effect was observed with 100 mM 3-amino-1,2,4-triazole. Under all conditions of incubation tested, the microbodies were completely unreactive to DAB staining, which was utilized as the basis for their identification. These organelles are rounded, moderately electron-opaque bodies with a finely granular matrix and fine tubules or cores and are limited by a single membrane. Under normal staining method, the microbodies were indistinguishable from the rounded sections of mitochondria.
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PMID:Ultrastructural localization of diaminobenzidine reactivity in leishmania donovani promastigotes. 19 23

A c-type cytochrome, cytochrome c-552, from a soluble fraction of an extreme thermophile, Thermus thermophilus HB8, was highly purified and its properties investigated. The absorption peaks were at 552, 522, and 417 nm in the reduced form, and at 408 nm in the oxidized form. The isoelectric point was at PH 10.8, the midpoint redox potential was about +0.23 V, and the molecular weight was about 15,000. The cytochrome c-552 was highly thermoresistant. The cytochrome reacted rapidly with pseudomonas aeruginosa nitrite reductase [EC 1.9.3.2], but slowly with bovine cytochrome oxidase [EC 1.9.3.1], yeast cytochrome c peroxidase [EC 1.11.1.5], or Nitrosomonas europaea hydroxylamine-cytochrome c reductase [EC 1.7.3.4].
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PMID:Purification and some properties of cytochrome c-552 from an extreme thermophile, Thermus thermophilus HB8. 19 83

Intracellular amastigotes of Leishmania donovani obtained from spleens of infected hamsters were studied by means of the diaminobenzidine technique for the presence of cytochromes and the activities of cytochrome oxidase and peroxidase. In the absence of H2O2, the oxidation of DAB, evidenced by electron-dense deposits localized on the cristae, inclusions, and enveloping membranes of the mitochondria and kinetoplast, revealed the activity of the cytochrome oxidase and the presence of the cytochromes. The increased deposition of DAB oxidation especially on the enveloping membranes in the presence of H2O2 suggests the activity of a peroxidase, probably cytochrome c peroxidase.
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PMID:Leishmania donovani: ultrastructural localization of diaminobenzidine reactivity in the amastigotes. 21 7

A model is proposed for the respiratory adaptation to falling oxygen concentration during growth of the microaerophilic bacterium Campylobacter mucosalis. During the early stages of growth, the oxidation of formate is a two-stage branched process involving the production of H2O2 followed by its peroxidatic removal. In later stages of growth, at lower oxygen concentrations, the predominant electron flow is linear to a membrane-bound cytochrome-c oxidase which reduces O2 directly to H2O. Several components of this model have been investigated. H2O2 was produced during formate oxidation and accumulated when electron transfer to the cytochrome-c peroxidase was inhibited. A cytochrome c-553, of the Class 1 types, was purified and shown to be the specific electron donor to both the peroxidase and the membrane-bound oxidase. The levels of this cytochrome c and of the peroxidase were higher in cells harvested early in growth. In later stages of growth, the activity of the membrane-bound oxidase increased. Proton pumping across the membrane was detected with either H2O2 or oxygen as terminal electron acceptor. The novel energy-conserving role of H2O2 in this catalase-negative bacterium is discussed in relation to its microaerophilic nature.
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PMID:The microaerophilic respiration of Campylobacter mucosalis. 283 75

The reaction of peroxide with cytochrome oxidase generates a peroxide compound having a Soret maximum at 428 nm. X-ray absorption spectroscopy analysis of the local structure of the active site iron shows marked similarity to that of the cytochrome c peroxidase intermediate Compound ES, which contains a short iron to proximal nitrogen distance compared to globins. Reductive titration of the 580 nm band of this compound indicates that the iron is one oxidizing equivalent above the resting oxidized form. These results support the presence of a ferryl iron (Fe(IV) = O) in the peroxide compound similar to that found for the peroxidases.
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PMID:Does the peroxide compound of cytochrome oxidase contain a ferryl iron? 283 66

An analysis of the effect of electrostatic properties of 4-carboxy-2,6-dinitrophenyllysine (CDNP-lysine) cytochromes c on their reactions with strongly and weakly binding redox partners is given. For strongly binding systems (cytochrome-c oxidase, cytochrome-c reductase, sulphite oxidase and yeast cytochrome-c peroxidase) the magnitude of the dipole moments of the CDNP cytochromes c determines their relative reactivities. For weakly binding redox agents, such as hexacyanoferrate(III), cobalt(III)tris(1,10-phenanthroline), azurin and plastocyanin, the electrostatic potential at the haem edge accounts for the greater part of the relative activities. Relative rate data were obtained from the literature. It is concluded that the dipole moment of native cytochromes c may account for an approx. 50-fold increase in the efficiency of its physiological activity towards membrane-bound enzymes. A correction on a formula to describe the contribution of a molecular dipole moment to the ionic strength dependence of a bimolecular rate constant (Koppenol, W. H. (1980) Biophys. J. 29, 493-508) leads to an equation nearly identical to that obtained by Van Leeuwen et al. (Van Leeuwen, J.W., Mofers, F.J.M. and Verrman, E.C.I. (1981) Biochim. Biophys. Acta 635, 434-439).
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PMID:Electrostatic interactions of 4-carboxy-2,6-dinitrophenyllysine-modified cytochromes c with physiological and non-physiological redox partners. 284 52

Lysine 32 has been previously implicated by chemical modification and modeling studies as a key component of the domain which controls recognition and binding of cytochrome c to its physiological partners, e.g. cytochrome b2, cytochrome c peroxidase, and cytochrome oxidase. In order to quantitate the importance of this residue, we have investigated the role of Lys-32 in the reactivity of cytochrome c in redox reactions in vitro and in vivo with protein partners by using a series of altered forms of iso-1-cytochrome c from the yeast Saccharomyces cerevisiae in which Lys-32 is replaced by Leu-32, Gln-32, Trp-32, and Tyr-32. Leu-32 and Gln-32 represent substitutions which change charge without seriously affecting the steric bulk of the side chain or the stability of the protein. For the Leu-32- and Gln-32-altered proteins, steady state kinetic studies with cytochrome c peroxidase, cytochrome b2, and cytochrome oxidase showed that neither of the steady state kinetic parameters, Km nor Vmax, were substantially modified by mutation. Studies of single turnover kinetics with a small molecule (ascorbate) or within bound complexes with either cytochrome b5 or cytochrome c peroxidase demonstrated that redox kinetics are only slightly affected by these substitutions. NMR experiments demonstrated that the Gln-32-altered protein can still bind strongly to a physiological partner, cytochrome c peroxidase. Growth in lactate medium demonstrated that the activity in vivo compared with the normal value was reduced to only 85% with the Gln-32- and Leu-32-altered proteins and to 65% with the Trp-32- and Tyr-32-altered proteins. These findings suggest that the evolutionary invariance of Lys-32 reflects only small quantitative changes in the binding and reactivity of cytochrome c.
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PMID:Replacements of lysine 32 in yeast cytochrome c. Effects on the binding and reactivity with physiological partners. 284 32

Phenylalanine 87 of yeast iso-1-cytochrome c (Phe 82 in horse heart and bonito) is phylogenetically conserved and occurs near the surface of the protein. It has been suggested that this residue is directly involved in electron transfer between cytochrome c and cytochrome c peroxidase (CCP) and may also control the polarity of the haem environment. Because Phe residues are not susceptible to chemical modification, no direct means of studying the functional role of Phe 87 has been available, so we have chosen Phe 87 as our initial target here to test the feasibility of using site-directed mutagenesis as a means of studying structure-function relationships in cytochrome c. We have changed the codon for Phe 87 to that of either a Ser, a Tyr or a Gly. The mutated genes have been introduced into a yeast strain lacking both isozymes of cytochrome c. Unlike the recipient strain, transformants grow on a non-fermentable carbon source, indicating that the mutant proteins can reduce cytochrome oxidase. The purified mutant proteins are similar to wild type with respect to their visible spectra, 20-70% as active as wild-type protein in the CCP assay, and their reduction potentials are lowered by as much as 50 mV. Thus Phe 87 is not essential for cytochrome c to transfer electrons but is involved in determining the reduction potential.
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PMID:Site-directed mutagenesis of cytochrome c shows that an invariant Phe is not essential for function. 298 14

Beef heart cytochrome c oxidase contains two cytochromes, a and a3, and Pseudomonas aeruginosa cytochrome c peroxidase has one high- and one low-potential c haem, cHP and cLP. The parallelism in co-ordination and spin states between cytochrome a and haem cHP on the one hand and between cytochrome a3 and haem cLP on the other is illustrated. The two latter haems become accessible to cyanide, when the former are reduced. Such reduction also leads to an activation of the enzymes. Mechanisms are presented in which ferryl forms of cytochromes a3 and haem cLP take part. The enzymes reach an oxidation state, formally the same as resting enzyme, but with different properties.
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PMID:Electron-paramagnetic-resonance studies of structure and function of the two-haem enzymes Pseudomonas cytochrome c peroxidase and beef heart cytochrome c oxidase. 299 75

The proteolytic processing of the mitochondrially encoded subunit II of cytochrome oxidase is prevented by the yeast mutation ts2858. We report that the mutant is, in addition, temperature sensitive for the processing of cytochrome b2, a protein encoded by nuclear DNA. Thus the same mutation affects the removal of pre-sequences from a mitochondrially encoded inner membrane protein and from an imported soluble protein located in the intermembrane space. The mutation blocks the second processing step of cytochrome b2. The cytochrome b2 intermediate accumulates in the mutant at 36 degrees C and assumes its enzyme activity. At 23 degrees C the conversion to the mature protein is considerably slower than in wild-type cells. The similarity of the cleavage sites Asn-Asp and Asn-Glu of the precursors for cytochrome oxidase subunit II and cytochrome b2, respectively, suggests a sequence-specific recognition by one protease or a factor activating a protease. On the other hand maturation of cytochrome c peroxidase, another enzyme of the intermembrane space, is not affected by the pet ts2858 mutation.
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PMID:One nuclear gene controls the removal of transient pre-sequences from two yeast proteins: one encoded by the nuclear the other by the mitochondrial genome. 301 96


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