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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 cytochrome oxidase (EC 1.9.3.1) of Rhodopseudomonas palustris was extracted with Triton X-100 plus KCl, from the membrane fraction of cells grown aerobically in the dark. The solubilized enzyme was purified by (NH4)2SO4 precipitation and chromatography on DEAE-cellulose. The purification resulted in a 108-fold enrichment of cytochrome oxidase on the basis of specific activity when compared to the membrane fraction. The purified enzyme was phosphate-sensitive (less than mM), oxidized reduced bovine, horse and yeast cytochrome c, and was inhibited 50% by 0.5 muM KCN or 7 muM NaN3. The native purified preparation migrated as one band in polyacrylamide gel electrophoresis. In the presence of dodecylsulfate four major polypeptides with apparent molecular weights of 30500, 25500, 12200 and 9500 were observed. The enzyme reacted with oxygen via cytochrome o. The purified preparation contained cytochrome c but was free of flavoproteins and NADH-linked and succinate-linked enzyme activities of the respiratory chain.
Eur J Biochem 1976 Sep
PMID:Isolation and partial characterization of the cytochrome oxidase from Rhodopseudomonas palustris. 0 86

Oxidized and reduced manganese cytochromes c, Mn Cyt c+ and Mn Cyt c, have been synthesized. Mn Cyt c+ and Fe Cyt c+ have identical electrophoretic and ion exchange mobilities. Mn Cyt c+ does not bind F-, CN-, or N3- ions; Mn Cyt c does not bind CO or O2. Mn Cyt c is very rapidly autooxidized by O2 even at -50 degrees. The manganese ion is readily dissociated from Mn Cyt c at acidic pH values. Both Mn Cyt c and Mn Cyt c+ are high spin complexes with 3d5 S = 5/2 and 3d4 S = 2 electronic configurations, respectively. The epr spectrum of Mn Cyt c is rhombic with (formula: see text). Both oxidized and reduced Mn Cyt c react with NO; the former reaction is reversible and the product has the following epr spectral parameters: (formula: see text). There is no superhyperfine interaction observable with the NO ligand, and the unpaired electron density is estimated to be mostly in the metal ion d xy orbital. The structure is best formulated as Mn Cyt c (NO)+. The half-reduction potential of Mn Cyt c is + 60 +/- 40 mV. It is neither oxidized by cytochrome oxidase nor reduced by NADH, NADPH, or succinate cytochrome reductase. These physical, chemical, and enzymic properties of manganese cytochromes c suggest a five-coordinate metalloporphyrin prosthetic group with the manganese ion situated significantly out-of-plane toward the side of His-18.
J Biol Chem 1977 Sep 10
PMID:Manganese cytochrome c. Structure and properties. 1 68

Four cytoplasmic mutants of Saccharomyces cerevisiae showing loss of mitochondrial rutamycin-sensitive ATPase activity but having significant cytochrome oxidase and NADH-cytochrome c reductase have been isolated. Genetic studies indicate the mutations to be closely linked to each other and have been assigned to a new locus, PHO1. The mutations show a low frequency of recombination with the OL12 locus, suggesting a linkage to this marker. They are not, however, linked to the OLI1 locus. Linkage of the ATPase mutations to the OLI2 locus is also indicated by restoration of wild-type diploids by sigma- clones that retain the segment of mitochondrial DNA carrying OLI2. Based on the recombinants issued from crosses of the mutants with a triple drug-resistant strain and an analysis of the resistance markers present in sigma- clones that are effective in restoring a wild-type phenotype, the PHO1 locus has been placed in the segment of DNA located between PAR1 and OLI2.
Eur J Biochem 1976 Sep
PMID:Localization on mitochondrial DNA of mutations leading to a loss of rutamycin-sensitive adenosine triphosphatase. 13 92

A Mendelian mutation, r-1, in Chlamydomonas reinhardtii has been isolated which elevates protoporphyrin accumulation of the Mendelian protoporphyrin mutants brS-1 and brC-1 more than 20 fold. This increased protoporphyrin accumulation is shown to result from increased delta-aminolevulinic acid synthesis in the double mutants brS-1 r-1 and brC-1 r-1 over that of brS-1 and brC-1 alone. By itself, the r-1 mutation has no detectable protoporphyrin accumulation and has reduced levels of delta-aminolevulinic acid synthesizing activity, chlorophyll, protoheme, and cytochrome oxidase activity. The low levels of chlorophyll and protoheme in r-1 can be increased by feeding delta-aminolevulinic acid. We hypothesize that r-1 may be a mutation of the gene coding for the delta-aminolevulinic acid synthesizing enzyme which reduces the sensitivity of this enzyme to feedback inhibition by protoporphyrin or heme as well as reducing the overall activity of the enzyme. Evidence is also presented for a single delta-aminolevulinic acid synthesizing enzyme serving both chlorophyll and heme biosynthesis.
Cell 1975 Sep
PMID:Genetic control of chlorophyll biosynthesis in chlamydomonas: analysis of a mutant affecting synthesis of delta-aminolevulinic acid. 17 3

Reactivity of mitochondria and peroxisomes to diaminobenzidine was investigated in Tetrahymena pyriformis and in wild-type and cytochrome oxidase-deficient Paramecium aurelia. Wild-type and cytochrome oxidase-deficient Paramecium gave positive mitochondrial reactions in the absence of added H2O2, and the deposits were enhanced by the addition of H2O2, whereas Tetrahymena gave positive mitochondrial reactions only upon addition of H2O2. These results are discussed in the light of the current ideas concerning the mechanism of staining by diaminobenzidine. Peroxisome-like organelles which react positively to diaminobenzidine, the reaction being partially inhibited by aminotriazole, were identified in both protozoa.
J Histochem Cytochem 1975 Sep
PMID:Diaminobenzidine reactivity of mitochondria and peroxisomes in Tetrahymena and in wild-type and cytochrome oxidase-deficient Paramecium. 17 Mar 31

Rat liver mitochondrial enzyme activities were measured after exposing the animals to the atmospheric pressure of 380 mm Hg for 5 h and 14 days. Succinate dehydrogenase and succinate oxidase activities increased significantly during the hypoxic period of 14 days. No change was observed in cytochrome oxidase activity. Malate dehydrogenase and glutamate dehydrogenase activities increased somewhat, but not significantly. The efficiency of oxidative phosphorylation (the ADP:O ratio) in the isolated mitochondria remained unchanged. The exact mitochondrial protein values showed a 15% decrease as compared with the control group. The concentrations of cytochromes did not change significantly in the hypoxic group. During the short hypoxic period succinate dehydrogenase, succinate oxidase and cytochrome oxidase activities increased as compared with those in the control group.
Acta Physiol Scand 1975 Sep
PMID:Rat liver mitochondrial enzyme activities in hypoxia. 17 Jul 95

A new method was devised for the isolation of foetal and neonatal rat lvier mitochondria, giving higher yields than conventional methods. 2. During development from the perinatal period to the mature adult, the ratio of cytochrome oxidase/succinate-cytochrome c reductase changes. 3. The inner mitochondrial membrane of foetal liver mitochondria possesses virtually no osmotic activity; the permeability to sucrose decreases with increasing developmental age. 4. Foetal rat liver mitochondria possess only marginal respiratory control and do not maintain Ca2+-induced respiration; they also swell in respiratory-control medium in the absence of substrate. ATP enhances respiratory control and prevents swelling, adenylyl imidodiphosphate, ATP+atractyloside enhance the R.C.I. (respiratory control index), Ca2+-induced respiratory control and prevent swelling, whereas GTP and low concentrations of ADP have none of these actions. It is concluded that the effect of ATP depends on steric interaction with the inner mitochondrial membrane. 5. When 1-day pre-partum foetuses are obtained by Caesarean section and maintained in a Humidicrib for 90 min, mitochondrial maturation is "triggered", so that their R.C.I. is enhanced and no ATP is required to support Ca2+-dependent respiratory control or to inhibit mitochondrial swelling. 6. It is concluded that foetal rat liver mitochondria in utero do not respire, although they are capable of oxidative phosphorylation in spite of their low R.C.I. The different environmental conditions which the neonatal rat encounters ex utero enable the hepatic mitochondria to produce ATP, which interacts with the inner mitochondrial membrane to enhance oxidative phosphorylation by an autocatalytic mechanism.
Biochem J 1975 Sep
PMID:The maturation of the inner membrane of foetal rat liver mitochondria. 17 46

Incubation of inner mitochondrial membranes from rat liver in the presence of inducers of peroxidation reactions, such as ascorbate or cysteine, produced a large loss in cytochrome oxidase activity parallel to the disappearance of phosphatidylcholine and phosphatidylethanolamine molecular species, which contained a saturated and an unsaturated fatty acid. The loss in enzyme activity was unrelated to alterations in other species of these phospholipids or other ones. These results may reflect the existence of specific associations within the membrane between cytochrome oxidase and monosaturated phosphatidylcholines and/or phosphatidylethanolamines.
Rev Esp Fisiol 1976 Sep
PMID:Relationship between losses in cytochrome oxidase activity and peroxidation of monosaturated phosphatidylcholines and phosphatidylethanolamines. 18 69

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.
Biochem J 1976 Sep 01
PMID:Studies on partially reduced mammalian cytochrome oxidase reactions with ferrocytochrome c. 18 26

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.
Can J Genet Cytol 1976 Sep
PMID:The function of mitochondrial genes in Neurospora crassa. 18 90


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