Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have identified two distinct pools of superoxide dismutase in fractions of human peripheral neutrophils obtained by the isopycnic fractionation of homogenates of the latter with linear sucrose gradients. Superoxide dismutase activity, observed with polyacrylamide gels impregnated with Nitro Blue Tetrazolium, was present in: (1) the mitochondrial fraction [density (rho) 1.169g/ml], containing the high-molecular-weight KCN-resistant enzyme, and (2) the cytoplasm fraction, containing the low-molecular-weight KCN-sensitive enzyme. Superoxide dismutase activity, observed with a quantitative assay involving cytochrome c, was present in: (1) the mitochondria, (2) the cytoplasm, and (3) the azurophil-granule fractions (rho=1.206 and 1.222g/ml). No substantial enzyme activity was observed in specific-granule fractions (rho=1.187g/ml) or in the membranous fraction (rho=1.136g/ml) in either assay. The apparent superoxide dismutase activity observed in the azurophil granules with the cytochrome c assay was attributable not to true superoxide dismutase but to myeloperoxidase, an enzyme found solely in the azurophil granules. In the presence of H(2)O(2), human neutrophil myeloperoxidase oxidized ferrocytochrome c. Thus, in the cytochrome c assay for superoxide dismutase, the oxidation of ferrocytochrome c by myeloperoxidase mimicked the inhibition of reduction of ferricytochrome c by superoxide dismutase. When myeloperoxidase was removed from azurophilgranule fractions by specific immuno-affinity chromatography, both myeloperoxidase and apparent superoxide dismutase activities were removed. It is concluded that there is no detectable superoxide dismutase in either the azurophil or specific granules of human neutrophils. Mitochondrial superoxide dismutase, 15% of the total dismutase activity of the cells, occurred only in fractions of density 1.160g/ml, where isocitrate dehydrogenase and cytochrome oxidase were also observed.
 ...
PMID:Subcellular distribution of superoxide dismutases in human neutrophils. Influence of myeloperoxidase on the measurement of superoxide dismutase activity. 19 57

Oxidative titrations were performed on the electrostatic complex formed between cytochrome c and cytochrome aa3 at low ionic strength. Midpoint potentials of the redox centers in the proteins in 1:1 and 2:1 complexes were compared with those in mixtures of the cytochromes at high ionic strength. Computer simulations of all titrations yielded midpoint potentials for the components of cytochrome aa3 which were consistent with literature values for isolated cytochrome aa3 or mixture of cytochromes c and aa3. However, the unequal heme extinction coefficients observed previously (Schroedl, N.A., and Hartzell, C.R. (1977), Biochemistry 16, 1327) during oxidative titrations of cytochrome aa3 became equal in magnitude under these experimental conditions. The binding of cytochrome c to cytochrome aa3 changed the midpoint potentials of cytochrome aa3 by 15-20 mV, while the midpoint potentials for cytochrome c were altered by 50-60 mV. Careful analysis of these titrations including computer simulation revealed that cytochrome c was able to bind to cytochrome aa3 only after cytochrome aL2+ had become oxidized. When bound to cytochrome aa3, the midpoint potential of cytochrome c was 210 7V. Titrations performed under a carbon monoxide atmosphere revealed cytochrome aa3 midpoint potentials unchanged from reported values. Cytochrome c again exhibited a midpoint potential of 210 mV after binding to cytochrome aa3.
 ...
PMID:Oxidative titrations of reduced cytochrome aa3: influence of cytochrome c and carbon monoxide on the midpoint potential values. 19 44

The reaction of cytochrome c with trifluoromethylphenyl isocyanate was carried out under conditions which led to the modification of a small number of the 19 lysines. Extensive ion-exchange chromatography was used to separate and purify six different derivatives, each modified at a single lysine residue, lysines 8, 13, 27, 72, 79, and 100, respectively. The only modifications which affected the activity of cytochrome c with cytochrome oxidase (EC 1.9.3.1) were those of lysines immediately surrounding the heme crevice, lysines 13, 27, 72, and 79, and also lysine 8 at the top of the heme crevice. In each case, the modified cytochrome c had the same maximum velocity as that of native cytochrome c, but an increased Michaelis constant for high affinity phase of the reaction. This supports the hypothesis that the cytochrome oxidase reaction site is located in the heme crevice region, and the highly conserved lysine residues surrounding the heme crevice are important in the binding.
 ...
PMID:Use of specific lysine modifications to locate the reaction site of cytochrome c with cytochrome oxidase. 19 45

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].
 ...
PMID:Purification and some properties of cytochrome c-552 from an extreme thermophile, Thermus thermophilus HB8. 19 83

Cytochrome c oxidase activity and cytochromes b, (c+c1) and a(+a3) concentrations were determined in liver mitochondria from rats fed the following diets: controls (group 1) fed ad libitum, energy-restricted (group 2) and protein-deficient (group 3). The animals were fed for two time intervals, 3--5 and 7--9 weeks. At 3--5 weeks, the cytochrome oxidase specific activity (nmol cytochrome c oxidized/mg protein/min) and cytochrome concentrations (nmol/mg protein) were not different in groups 2 and 3 as compared to group 1. At 7--9 weeks, the cytochrome oxidase specific activity and concentrations of cytochromes b, (c+c1) and a(+a3) were significantly reduced in group 2 rats as compared to well-fed controls. The Michaelis-Menten constant, Km apparent for ferrocytochrome c, was significantly higher in group 2 as compared to group 1. In group 3 rats, cytochrome oxidase specific activity and cytochrome b, a(+a3) concentrations were not different from group 1 at 7-9 weeks. However, cytochrome (c+c1) concentration was higher in group 3, resulting in an elevated ratio of cytochrome (c+c1) to cytochrome a(+a3) as compared to groups 1 and 2.
 ...
PMID:Rat liver mitochondrial cytochrome c oxidase and cytochromes in experimental protein-energy malnutrition. 20 90

The luminescent properties of metal-free, tin(IV) and zinc(II) cytochromes c have been used to characterize the interaction of cytochrome c with mitochondria and cytochrome oxidase. Diminution in the fluorescence yields of tin and zinc cytochrome c occur when these derivates bind to cytochrome oxidase or mitochondria. Based upon spectral overlap and quantum yield, the distance between the porphyrin rings of cytochrome a and cytochrome c is estimated according to Forster theory to be in the neighborhood of 3.5 nm. Measurements of the polarized emission of metal-free 'porphyrin' cytochrome c when bound to oriented layers of cytochrome c oxidase indicate that the porphyrin is bound obliquely to the plane of the oxidase layers with an angle of about 70 degrees C from heme plane to membrane plane. It is proposed that these data have significance for elucidation of electron transfer mechanisms.
 ...
PMID:Metal-free and metal-substituted cytochromes c. Use in characterization of the cytochrome c binding site. 20 55

Dehydrogenases of glycolysis, Kreb's cycle, and pentose-phosphate shunt were detected in cystozoites of Toxoplasma gondii strain SS-119 with various degrees of activity. A mixed oxidative metabolism may be postulated on this stage of the toxoplasma life cycle. Besides, the activity of cytochrome oxidase was detected in cystozoites; the addition of cytochrome c to the incubation medium significantly intensified the reaction intensity. Of interest seems the observation of a layer of higher enzymatic activity in the host brain tissue in the immediate neighbourhood with the cyst body. This may be regarded as the host cells' (or tissue') response to the presence of the parasite's alien body.
 ...
PMID:[Cytochemical study of different stages in the life cycle of Toxoplasma gondii. VII. Oxidation--reduction enzymes in the cyst forms]. 20 66

Isolated rat heart was perfused with Langendorff's retrograde perfusion method, while the oxygen consumption and the left ventricular pressure were monitored continually. The steady-state contents of metabolites in the cardiac tissue, freeze clamped under various work-load conditions, were determined and the concentrations of free cytosolic ADP and AMP were calculated from the near equilibrium in creatine phosphokinase and adenylate kinase reactions. Increasing respiratory rate with increasing load was accompanied by a fall in the cytosolic free [ATP]/[ADP][Pi] but little change in the mitochondrial free [NAD+]/[NADH]. The free energy of ATP hydrolysis was calculated from the concentrations of the adenine nucleotides and compared with the values computed from the measured turnover number for cytochrome c and redox state of the mitochondrial NAD couple according to a mathematical model. The agreement between the two values was good over a wide range of metabolic conditions, which provides further support for the proposed near-equilibrium model of mitochondrial respiration with control exerted at the cytochrome oxidase-oxygen reaction.
 ...
PMID:Energy relationships between cytosolic metabolism and mitochondrial respiration in rat heart. 20 95

Kinetic studies of the reactions of selected eukaryotic and prokaryotic cytochromes c with mitochondrial cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase (EC 1.9.3.1) using a standardized complex IV preparation from beef heart are reported. Data on reactions with NADH-linked cytochrome c reductase (complexes I and III) are included. The concentration ranges employed provide a basis for quantitative demonstration of a general rate law applicable to oxidase reactions of cytochrome c of greatly differing reactivities. Results are interpreted on the basis of a modified Minnaert mechanism (Minnaert, K. (1961) Biochim. Biophys. Acta 50, 23), assuming productive complex formation between cytochrome c and free oxidase in addition to further complex binding of a second cytochrome c molecule to the initially formed oxidase complex. Kinetic constants so obtained are consistent with the assumption that binding is the dominant parameter in reactivity, and can be rationalized most simply on this basis.
 ...
PMID:Comparative kinetic studies of cytochromes c in reactions with mitochondrial cytochrome c oxidase and reductase. 20 37

Cytochrome c derivatives labeled with a 3-nitrophenylazido group at lysine 13, at lysine 22, or at both residues have been prepared. The interaction of the cytochrome c derivatives with beef heart cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) in the presence of ultrviolet light results in formation of a covalent complex between cytochrome c and the oxidase. Using the lysine 22 derivative, the polypeptide composition of the oxidase is not modified, nor is its catalytic activity, whereas with the lysine 13 derivative, the gel electrophoretic pattern is altered and the catalytic activity of the complex diminished. The data are consisten with a specfic covalent interaction of the lysine 13 derivative of cytochrome c with the polypeptide of molecular weight 23,700 (Subunit II) of cytochrome c oxidase.
 ...
PMID:Interaction of cytochrome c with cytochrome c oxidase. Photoaffinity labeling of beef heart cytochrome c oxidase with arylazido-cytochrome c. 20 34


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