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)

Cytochrome P-450 was shown to be involved in 11 alpha-, and 11 beta-hydroxylation of Substance S in intact C. elegans protoplasts. The steroid transformation was inhibited by carbon monoxide, the inhibitory effect being dependent on CO concentration. The function of cyt P-450 in intact protoplasts was confirmed by the estimation of strong absorption at 450 nm in the CO difference spectrum. The presence of antimycin A was necessary to prevent the reduction of the cytochrome oxidase and its interference with the cyt P-450 in the spectrophotometric analysis. The intracellular content of cyt P-450 could be increased from 5.25 pM/mg protein to 26.88 pM/mg protein when the steroid inducer was present in the medium at each stage of protoplast preparation and during cyt P-450 determination. The enriched microsomal fraction obtained from the crude extract of ruptured protoplasts contained the steroid 11 alpha-hydroxylase system of C. elegans. The activity of 11 beta-hydroxylase could not be detected under the conditions of the experiment. The localization of steroid hydroxylases of C. elegans in microsomes was confirmed by cyt P-450 detection in the 9600 x g supernatant. Membranous fractions (pellets 1100 x g and 9600 x g) of the concanavaline A stabilized protoplasts, carrying the marker plasma-membrane-bound and mitochondrial ATPases, did not show maximum absorption at 450 nm in the CO difference spectrum.
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PMID:Determination of cytochrome P-450 in Cunninghamella elegans intact protoplasts and cell-free preparations capable of steroid hydroxylation. 181 23

Further genetic evidence is provided here that Bradyrhizobium japonicum possesses a mitochondria-like electron-transport pathway: 2[H]----UQ----bc1----c----aa3----O2. Two Tn5-induced mutants, COX122 and COX132, having cytochrome c oxidase-negative phenotypes, were obtained and characterized. Mutant COX122 was defective in a novel gene, named cycM, which was responsible for the synthesis of a c-type cytochrome with an Mr of 20,000 (20K). This 20K cytochrome c appeared to catalyse electron transport from the cytochrome bc1 complex to the aa3-type terminal oxidase and, unlike mitochondrial cytochrome c, was membrane-bound in B. japonicum. The Tn5 insertion of mutant COX132 was localized in coxA, the structural gene for subunit I of cytochrome aa3. This finding also led to the cloning and sequencing of the corresponding wild-type coxA gene that encoded a 541-amino-acid protein with a predicted Mr of 59,247. The CoxA protein shared about 60% sequence identity with the cytochrome aa3 subunit I of mitochondria. The B. japonicum cycM and coxA mutants were able to fix nitrogen in symbiosis with soybean (Fix+). In contrast, mutants described previously which lacked the bc1 complex did not develop into endosymbiotic bacteroids and were thus Fix-. The data suggest that a symbiosis-specific respiratory chain exists in B. japonicum in which the electrons branch off at the bc1 complex.
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PMID:Genetic analysis of the cytochrome c-aa3 branch of the Bradyrhizobium japonicum respiratory chain. 196 17

Under anaerobic circumstances in the presence of nitrate Paracoccus denitrificans is able to denitrify. The properties of the reductases involved in nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase are described. For that purpose not only the properties of the enzymes of P. denitrificans are considered but also those from Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas stutzeri. Nitrate reductase consists of three subunits: the alpha subunit contains the molybdenum cofactor, the beta subunit contains the iron sulfur clusters, and the gamma subunit is a special cytochrome b. Nitrate is reduced at the cytoplasmic side of the membrane and evidence for the presence of a nitrate-nitrite antiporter is presented. Electron flow is from ubiquinol via the specific cytochrome b to the nitrate reductase. Nitrite reductase (which is identical to cytochrome cd1) and nitrous oxide reductase are periplasmic proteins. Nitric oxide reductase is a membrane-bound enzyme. The bc1 complex is involved in electron flow to these reductases and the whole reaction takes place at the periplasmic side of the membrane. It is now firmly established that NO is an obligatory intermediate between nitrite and nitrous oxide. Nitrous oxide reductase is a multi-copper protein. A large number of genes is involved in the acquisition of molybdenum and copper, the formation of the molybdenum cofactor, and the insertion of the metals. It is estimated that at least 40 genes are involved in the process of denitrification. The control of the expression of these genes in P. denitrificans is totally unknown. As an example of such complex regulatory systems the function of the fnr, narX, and narL gene products in the expression of nitrate reductase in E. coli is described. The control of the effects of oxygen on the reduction of nitrate, nitrite, and nitrous oxide are discussed. Oxygen inhibits reduction of nitrate by prevention of nitrate uptake in the cell. In the case of nitrite and nitrous oxide a competition between reductases and oxidases for a limited supply of electrons from primary dehydrogenases seems to play an important role. Under some circumstances NO formed from nitrite may inhibit oxidases, resulting in a redistribution of electron flow from oxygen to nitrite. P. denitrificans contains three main oxidases: cytochrome aa3, cytochrome o, and cytochrome co. Cytochrome o is proton translocating and receives its electrons from ubiquinol. Some properties of cytochrome co, which receives its electrons from cytochrome c, are reported.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolic regulation including anaerobic metabolism in Paracoccus denitrificans. 205 Jun 53

Paracoccus denitrificans is able to grow on the C1 compounds methanol and methylamine. These compounds are oxidized to formaldehyde which is subsequently oxidized via formate to carbon dioxide. Biomass is produced by carbon dioxide fixation via the ribulose biphosphate pathway. The first oxidation reaction is catalyzed by the enzymes methanol dehydrogenase and methylamine dehydrogenase, respectively. Both enzymes contain two different subunits in an alpha 2 beta 2 configuration. The genes encoding the subunits of methanol dehydrogenase (moxF and moxI) have been isolated and sequenced. They are located in one operon together with two other genes (moxJ and moxG) in the gene order moxFJGI. The function of the moxJ gene product is not yet known. MoxG codes for a cytochrome c551i, which functions as the electron acceptor of methanol dehydrogenase. Both methanol dehydrogenase and methylamine dehydrogenase contain PQQ as a cofactor. These so-called quinoproteins are able to catalyze redox reactions by one-electron steps. The reaction mechanism of this oxidation will be described. Electrons from the oxidation reaction are donated to the electron transport chain at the level of cytochrome c. P. denitrificans is able to synthesize at least 10 different c-type cytochromes. Five could be detected in the periplasm and five have been found in the cytoplasmic membrane. The membrane-bound cytochrome c1 and cytochrome c552 and the periplasmic-located cytochrome c550 are present under all tested growth conditions. The cytochromes c551i and c553i, present in the periplasm, are only induced in cells grown on methanol, methylamine, or choline. The other c-type cytochromes are mainly detected either under oxygen limited conditions or under anaerobic conditions with nitrate as electron acceptor or under both conditions. An overview including the induction pattern of all P. denitrificans c-type cytochromes will be given. The genes encoding cytochrome c1, cytochrome c550, cytochrome c551i, and cytochrome c553i have been isolated and sequenced. By using site-directed mutagenesis these genes were mutated in the genome. The mutants thus obtained were used to study electron transport during growth on C1 compounds. This electron transport has also been studied by determining electron transfer rates in in vitro experiments. The exact pathways, however, are not yet fully understood. Electrons from methanol dehydrogenase are donated to cytochrome c551i. Further electron transport is either via cytochrome c550 or cytochrome c553i to cytochrome aa3. However, direct electron transport from cytochrome c551i to the terminal oxidase might be possible as well.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:C1 metabolism in Paracoccus denitrificans: genetics of Paracoccus denitrificans. 205 Jun 54

An increase of proton permeability, creation of the possibility for the superoxide radical O2-. to escape and a decrease in the oxidation rate of acetyl-CoA due to the stress origin with such membrane-bound enzymes as succinate dehydrogenase and cytochrome oxidase remaining as active as they were, have been observed under the myocardial necroses reproduced after the endured stress in the internal mitochondrial membrane of the "non-ischemized" division of the left ventricle of the heart. Against a background of mitochondria denergization the content of non-esterified fatty acids in blood increases mainly as a result of the influx of non-esterified fatty acids of membrane origin.
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PMID:[Activity of enzymes of the internal membrane of heart mitochondria and spectrum of blood fatty acids during myocardial necrosis reproduced after the stress]. 215 66

Energy-dependent Ca2+ uptake was characterized in vesicles derived from rat submandibular salivary glands. Ca2+ transport was stimulated by submicromolar levels of Ca2+, reached a plateau at 1-20 microM Ca2+ then again increased as the Ca2+ concentration rose to millimolar levels. Ruthenium red (2.5 microM) was used to resolve this pattern of uptake into two components: ruthenium red-insensitive Ca2+ transport occurs in the presence of the dye, is stimulated by submicromolar Ca2+ concentrations and reaches a maximum steady state at about 1 microM Ca2+. The distribution of ruthenium red-insensitive Ca2+ uptake in membrane subfractions obtained by differential centrifugation is positively (r = 0.717) and significantly (p = 0.001) correlated with the distribution of membrane-bound RNA in the same subfractions. Ca2+ uptake which is abolished by ruthenium red is greatest at millimolar Ca2+ concentrations. Its distribution is positively (r = 0.828) and significantly (p = 0.0001) correlated with the cytochrome-c oxidase activity of the membrane subfractions but is unrelated to the distribution of particulate RNA and is negatively correlated with Na+-K+ ATPase activity. We conclude that vesicles derived from the endoplasmic reticulum of rat submandibular glands actively transport Ca2+ by a ruthenium red-insensitive mechanism which is stimulated at Ca2+ concentrations typical of the cytosol. Membranes derived from mitochondria also sequester Ca2+ but by a mechanism which is inhibited by ruthenium red and which reaches its maximum steady state capacity at relatively high Ca2+ concentrations.
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PMID:Characterization and localization of two forms of active Ca2+ transport in vesicles derived from rat submandibular glands. 242 Apr 66

Mitochondrial cytochrome oxidase is a functionally complex, membrane-bound respiratory enzyme which catalyses both the reduction of O2 to water and proton-pumping. During respiration, an exogenous donor, cytochrome c, donates four electrons to O2 bound at the bimetallic haem alpha 3 Fe-Cu centre within the enzyme. These four electron transfers are mediated by the enzyme's haem alpha and CuA redox centres and result in the translocation of four protons across the inner mitochondrial membrane. The molecular mechanism of proton translocation has not yet been delineated, however, and in the absence of direct experimental evidence all four electron transfers have been assumed to couple equally to proton-pumping. Here, I report the effects of proton-motive force and membrane potential on two equilibria involving intermediates of the bimetallic centre at different levels of O2 reduction. The results show that only two of the electron transfers, to the 'peroxy' and 'oxyferryl' intermediates of the bimetallic centre, are linked to proton translocation, a finding which strongly constrains candidate mechanisms for proton-pumping.
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PMID:Identification of the electron transfers in cytochrome oxidase that are coupled to proton-pumping. 246 60

COIII is one of the major subunits in the mitochondrial and a bacterial cytochrome c oxidase, cytochrome aa3. It does not contain any of the enzyme's redox-active metal centres and can be removed from the enzyme without major changes in its established functions. We have deleted the COIII gene from Paracoccus denitrificans. The mutant still expresses spectroscopically detectable enzyme almost as the wild-type, but its cytochrome c oxidase activity is much lower. From 50 to 80% of cytochrome a is reduced and its absorption maximum is 2-3 nm blue-shifted. The EPR signal of ferric cytochrome a is heterogeneous indicating the presence of multiple cytochrome a species. Proteolysis of the membrane-bound oxidase shows new cleavage sites both in COI and COII. DEAE-chromatography of solubilized enzyme yields fractions that contain a COI + COII complex and in addition haem-binding, free COI as well as free COII. The mutant phenotype can be complemented by introducing the COIII gene back to cells in a plasmid vector. We conclude that cytochrome oxidase assembles inefficiently in the absence of COIII and that this subunit may facilitate a late step in the assembly. The different oxidase species in the mutant represent either accumulating intermediates of the assembly pathway or dissociation products of a labile COI + COII complex and its conformational variants.
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PMID:Deletion of the gene for subunit III leads to defective assembly of bacterial cytochrome oxidase. 255 69

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

We have studied the reactions of the oxidase of Paracoccus dentrificans with its membrane-bound cytochrome c and with soluble cytochrome c550 of Paracoccus and of bovine heart. The turnover rate of Paracoccus oxidase with membrane-bound cytochrome c is high, approaching 1000/sec. at 25 degrees. When soluble cytochrome c is added to the electron transport chain oxidizing NADH or succinate, no increase in 02 uptake is observed. When the oxidase is reacting with the membrane-bound cytochrome c, the reaction site is not exposed for reaction with soluble cytochrome c. We have purified the Paracoccus oxidase, following relatively simple methodology. It has three major subunits similar in molecular weight to those of the larger subunits of the bovine oxidase. When reconstituted in the presence of asolectin, it is just as active as the intact membrane-bound oxidase in reaction with soluble cytochrome c. The soluble cytochrome c reacts directly with the cytochrome aa3. We found direct evidence that the oxidase is stimulated in the presence of low concentrations of cytochrome c. The stimulatory effect could be the explanation for the so-called "high affinity" site for reaction with cytochrome c. The reaction of bovine cytochrome c with Paracoccus oxidase resembles that with the bovine oxidase in every way tested. The Paracoccus oxidase must have a cytochrome c binding site equivalent to that of the bovine enzyme. The reaction of the Paracoccus oxidase with its own soluble cytochrome c550, which has a highly negative hemisphere on the side of the molecule away from the heme crevice, has different properties from those seen in its reaction with bovine cytochrome c. However the properties all change to be like those with bovine cytochrome c on addition of poly-L-lysine. These data emphasize the importance of all of the charged groups on the cytochrome c in influencing binding or electron transfer reactions. The respiratory chain on the membranes of a cytochrome c-deficient mutant can reduce cytochrome aa3 using NADH as substrate in a manner similar to that of the wild type, although at somewhat lower rate, suggesting diffusional encounter of the large complexes within the membrane. Our data permit speculations about the possible evolution from the bacterial to the mitochondrial electron transport system.
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PMID:Kinetics of the interaction of cytochrome c oxidase of Paracoccus denitrificans with Paracoccus and mitochondrial cytochrome c. 284 81


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