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:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Electron transport particles obtained from cell-free extracts of Propionibacterium shermanii by centrifugation at 105000 times g for 3 hrs oxidized NADH, D,L-lactate, L-glycerol-3-phosphate and succinate with oxygen and, except for succinate, with fumarate, too. 2. Spectral investigation of the electron transport particles revealed the presence of cytochromes b, d and o, and traces of cytochrome alpha1 and a c-type cytochrome. Cytochrome b was reduced by succinate to about 50%, and by NADH, lactate or glycerol-3-phosphate to 80--90%. 3. The inhibitory effects of amytal and rotenone on NADH oxidation, but not on the oxidation of the other substrates, indicated the presence of the NADH dehydrogenase complex, or "site I region", in the electron transport system of P. shermanii. 4. NQNO inhibited substrate oxidations by oxygen and fumarate, as well as equilibration of the flavoproteins of the substrate dehydrogenases by way of menaquinone. The inhibition occurred at low concentrations of the inhibitor and reached 80--100%, depending on the substrate tested. The site of inhibition of the respiratory activity was located between menaquinone and cytochrome b. In addition, inhibition of flavoprotein equilibration suggested that NQNO acted upon the electron transfer directed from menaquinol towards the acceptor to be reduced, either cytochrome b or the flavoproteins, which would include fumarate reductase. 5. In NQNO-inhibited particles, cytochrome b was not oxidized by oxygen-free fumarate, but readily oxidized by oxygen. It was concluded from this and the above evidence that the branching-point of the electron transport chain towards fumarate reductase was located at the menaquinone in P. shermanii. It was further concluded that all cytochromes were situated in the oxygen-linked branch of the chain, which formed a dead end of the system under anaerobic conditions. 6. Antimycin A inhibited only oxygen-linked reactions of the particles to about 50% at high concentrations of the inhibitor. Inhibitors of terminal oxidases were inactive, except for carbon monoxide.
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PMID:The electron transport system of the anaerobic Propionibacterium shermanii: cytochrome and inhibitor studies. 16 27

Cytochrome b-559 was isolated from spinach and the alga Bumilleriopsis filiformis (Xanthophyceae) and characterized by functional properties: (a) It was active as electron acceptor in a diaphorase system using NADPH as donor and ferredoxin and ferredoxin-NADP reductase as redox proteins. (b) It exhibited photooxidation with Photosystem-I particles, when illuminated with 707 nm light. (c) It was photooxidized by Photosystem-II particles and 652 nm light at room temperature. Light greater than 702 nm was ineffective. The data corroborate previous reports on redox reactions of bound cytochrome b-559.
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PMID:Some photoreactions of isolated cytochrome b-559. 91 18

1. Cytochrome b-562 is more reduced in submitochondrial particles of mutant 28 during the aerobic steady-state respiration with succinate than in particles of the wild type. When anaerobiosis is reached, the reduction of cytochrome b is preceded by a rapid reoxidation in the mutnat. A similar reoxidation is observed in the wild type in the present of low concentrations of antimycin. 2. In contrast to the wild type, inhibition of electron transport in the mutant has a much higher antimycin titre than effects on cytochromes b (viz., aerobic steady-state reduction; reduction in the presence of substrate, cyanide and oxygen; the 'red shift' and lowering of E'-o of cytochrome b-562). Moreover, the titration curve of electron transport is hyperbolic whereas the curves for the reduction are sigmoidal. The conclusion is, that in both mutant and wild type, the actions of antimycin on electron transport and cytochromes b are separable. 3. The red shift in the mutant is more extensive than in the wild type. 4. Cytochrome b-558 and cytochrome b-566 (that absorbs in mutant and wild type at 564.5 nm) do not respond simultaneously to addition of antimycin, indicating that they are two separate cytochromes. 5. The difference between the effect of antimycin on electron transport and cytochromes b reduction is also found in intact cells of the mutant. 6. A model is suggested for the wild-type respiratory chain in which (i) the cytochromes b lie, in an uncoupled system, out of the main electron-transfer chain, (ii) antimycin induces a conformation change in QH-2-cytochrome c reductase resulting in effects on cytochrome b and inhibition of electron transport, (iii) a second antimycin-binding site with low affinity to the antibiotic is present, capable of inhibiting electron transport.
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PMID:Antimycin-insensitive mutants of Candida utilis II. The effects of antimycin on Cytochrome b. 116 99

A new method of preparation of bovine polymorphonuclear leukocytes (PMN) is described. The subcellular distribution of cytochrome b in resting and activated bovine PMN was compared to that of the O2-.-generating oxidase (assessed as NADPH cytochrome c reductase inhibited by superoxide dismutase). In resting PMN and in PMN activated by phorbol myristate acetate (PMA), cytochrome b was located into two membrane fractions, one of which was enriched in plasma membrane and cosedimented with alkaline phosphatase, while the other consisted of a denser material cosedimenting with markers of the specific and azurophil granules, i.e. the vitamin-B12-binding protein and myeloperoxidase respectively. During activation of PMN by PMA, 15-20% cytochrome b migrated from dense granules to the plasma membrane. The distribution of the O2-. generating oxidase and cytochrome b in subcellular particles was studied during the course of phagocytosis of PMA-coated latex beads by bovine PMN. At the onset of the respiratory burst, the phagocytic vacuoles arising from internalization of the plasma membrane were enriched in oxidase and alkaline phosphatase, but their specific content of cytochrome b was limited; in contrast, cytochrome b was predominant in denser membrane fractions cosedimenting with myeloperoxidase and the vitamin-B12-binding protein. After a few minutes of phagocytosis, a fraction of light vacuoles, slightly denser than the phagocytic vacuoles, became enriched in O2-.-generating oxidase, cytochrome b, the vitamin-B12-binding protein and myeloperoxidase. These vacuoles probably arose from the fusion of the phagocytic vacuoles with dense granules. In bovine PMN supplemented with glucose and maintained in anaerobiosis, activation by PMA induced slow reduction of cytochrome b (60-70% in 15 min at 37 degrees C). Similar results were obtained with cytoplasts after activation by PMA (30% reduction in 3 min at 37 degrees C). Cytochrome b in a particulate fraction obtained by centrifugation at 100 000 X g of an homogenate of PMA-activated PMN, was slowly reduced upon addition of NADPH under anaerobiosis (less 20% in 20 min at 37 degrees C). No reduction occurred in the 100 000 X g fraction prepared from non-activated PMN. The Soret band of cytochrome b reduced by dithionite was displaced by CO only by 1-2 nm. At subsaturating concentrations, CO had no effect on the rate of O2 uptake by activated bovine PMN.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The respiratory burst of bovine neutrophils. Role of a b type cytochrome and coenzyme specificity. 405 28

1. A mehod for the isolation of a monodisperse ubiquinol-cytochrome c reductase (complex III) from beef heart mitochondria has been developed. The procedure consists of an enzyme solubilization in Triton X-100 followed by hydroxyapatite and gel chromatography. 2. The minimum unit of the isolated complex is composed of 9 polypeptide subunits with Mr of 49000, 47000, 30000, 25000, 12000, 11000 and 6000. It contains 8 mumol of cytochrome b, 4 mumol of cytochrome c1, 7-8 mumol of nonhemne iron, corresponding to 3.5-4 mumol of the Rieske iron-sulfur protein, less than 1.0 mumol of ubiquinone and about 60 mumol of phospholipids, per g of protein. The specific detergent binding amounts to 0.2g of Triton X-100 per g protein. 3. Cytochrome b exhibits an alpha-absorbance maximum at 562 nm. In redox titrations it reveals two half-reduction potentials, i.e. -10 and + 100 mV, at pH 7.0. The absorbance maximum of cytochrome c1 lies at 553 nm and its half-reduction potential amounts to +250 mV. 4. The reductase reveals electron-transferring activity with ubiquinol-1, -2, -3, and -9 as donor and cytochrome c as acceptor. The activity with ubiquinol-9 was analyzed according to the surface dilution scheme developed for the action of phospholipases. The molecular activity amounts to 75 mol of cytochrome c reduced per s at 20%C. 5. A dissociation constant K's of 5.5 mM has been determined for the Tritonsolubilized enzyme: ubiquinol-containing micelle association. In this case the total concentration of ubiquinol plus Triton X-100 has been substituted for the concentration of binding areas on the ubiquinol-containing micelles. This substitution makes the reasonable assumption that the sum of ubiquinol concentration plus Triton X-100 is proportional to the number of available binding areas. 6. A K'm value of 0.025 was found for ubiquinol-9. This is an analog to the Michaelis constant and is expressed as mol fraction of ubiquinol in the ubiquinol-Triton micelle.
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PMID:Ubiquinol-cytochrome c reductase (EC 1.10.2.2). Isolation in triton X-100 by hydroxyapatite and gel chromatography. Structural and functional properties. 625 May 88

An NADH-cytochrome c reductase (complex I-III) was isolated from Ascaris suum muscle mitochondria. The enzyme preparation catalyzed the reduction of 1.68 mumol cytochrome c min-1 mg-1 protein at 25 degrees C with NADH but not with NADPH, and retained its sensitivity to rotenone, piericidin A and 2-heptyl-4-hydroxyquinoline-N-oxide as with the submitochondrial particles. The isolated complex I-III, essentially free of succinate-cytochrome c reductase and cytochrome c oxidase, consisted of fourteen polypeptides with apparent molecular weights ranging from 76 000 to 12 000. The complex I-III contained three cytochromes, b-559.5, b-563 and c1-550.5 and Pigment-558 at concentrations of 1.28, 0.211, 1.23 and 0.321 nmol mg-1 protein, respectively. Cytochrome b-558, a major constituent cytochrome of Ascaris mitochondria and previously suggested to participate in the fumarate reductase system, was not fractionated in the complex I-III. Localization of the cytochromes in Ascaris electron transfer complexes is discussed.
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PMID:Electron transfer complexes of Ascaris suum muscle mitochondria: I. Characterization of NADH-cytochrome c reductase (complex I-III), with special reference to cytochrome localization. 651 90

NADPH-dependent O2- -generating activity was extracted and partially purified from guinea pig polymorphonuclear leukocytes. The most active preparation generated 202.8 nmol O2- min/min per mg protein. This activity was 30-fold higher than that of extracts from resting cells, indicating that the activated state of the oxidase was retained after solubilization. The solubilization and purification of the enzyme activity were followed by a parallel solubilization and purification of cytochrome b. Spectroscopic studies showed that solubilized cytochrome b has an Em of -245 mV and binds CO to about 30%. Cytochrome b was reduced by NADPH in anaerobiosis at a low rate and was rapidly reoxidized by air. A correlation was found between the inhibition of O2- formation caused by the SH reagent p-chloromercuribenzoate and the alterations induced by this compound on the Em of cytochrome b. These observations strongly support the participation of cytochrome b in the catalytic activity of the solubilized NADPH oxidase. The enzyme preparations contained FAD, which was found to be associated both with NADPH oxidase and with diaphorase activities. The fraction with the highest O2- forming activity contained FAD and cytochrome b in a ratio of about 0.5:1. The participation of FAD in the electron transport from NADPH to O2 is supported also by the inhibitory effect exerted by quinacrine on O2- formation.
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PMID:The cytochrome b and flavin content and properties of the O2- -forming NADPH oxidase solubilized from activated neutrophils. 687 Dec 31

This paper presents biochemical data upon a young male with a mitochondrial myopathy characterised by weakness, severe exercise intolerance, muscle wasting and exercise-induced lactic acidaemia. Two similar cases have been previously documented (Morgan-Hughes et al. 1979). This report more precisely locates the mitochondrial defect. In vitro mitochondrial studies show markedly decreased respiratory rates with all NAD-linked substrates whilst that with flavin-linked succinate is normal. Oxidative phosphorylation is normally coupled. Mitochondrial cytochrome components as determined by low temperature spectroscopy are normal. NADH-ferricyanide reductase and primary dehydrogenase activities are present at levels far in excess of that required to support normal NAD-linked substrate oxidation rates. Intramitochondrial NAD levels are similar to those found in other mammalian muscle. It is proposed therefore that the mitochondrial defect is situated between NADH dehydrogenase and the CoQ--Cytochrome b complex; possibly being a derangement of a non-haem iron sulphur centre.
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PMID:Mitochondrial myopathy. Biochemical studies revealing a deficiency of NADH--cytochrome b reductase activity. 722 53

Cytochrome b-c1 complex (ubiquinol-cytochrome c reductase) of beef heart mitochondria has been crystallized. Crystals grown in capillary tubes diffracted X-rays from a laboratory source to a resolution of 7 A and synchrotron radiation to a resolution of 4.5 A in the presence of mother liquor. However, the movement of crystals in the mother liquor makes data collection very difficult. Removal of the mother liquor from the crystals causes severe loss of diffraction quality. To circumvent these difficulties we have recently developed a method for crystallization of the cytochrome b-c1 complex from a gel. The sizes, shapes and diffraction qualities of crystals grown in gel approach those of crystals obtained from liquid. Preliminary experiments on a Xuong-Hamlin area detector indicate that these crystals have the symmetry of a body centered tetragonal space group with cell constants a = b = 157 A, c = 590 A. Assuming eight cytochrome b-c1 complex dimers per unit cell, the crystals have a solvent content of 70% (v/v). Under reduced pressure the crystallization time is significantly decreased. Although crystals obtained under reduced pressure are generally smaller, the shorter crystallization time provides an opportunity to explore more crystallization conditions.
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PMID:Crystallization of mitochondrial cytochrome b-c1 complex from gel with or without reduced pressure. 796 99

Nuclear respiratory deficient mutants of Saccharomyces cerevisiae have been screened for lesions in genes affecting ubiquinol-cytochrome c reductase activity. In the present study we describe a new gene, CBP4, whose encoded product is absolutely essential for the activity and expression of the respiratory enzyme. We have cloned and sequenced CBP4, which encodes a 20-kDa protein having no obvious homology to any known protein. cbp4 mutants are unable to respire due to specific loss of ubiquinol-cytochrome c reductase activity. cbp4 mutants demonstrate a pleiotropic reduction in the steady state levels of four subunits of ubiquinol-cytochrome c reductase, namely core 4, core 5, the Rieske protein and cytochrome b. Cytochrome b is not spectrally visible in the mutants, although transcription and translation of the apoprotein is normal. Antiserum prepared against a trpE/CBP4 gene fusion react with an 18.4-kDa mitochondrial protein in wild type yeast, but the protein is not found in a mutant containing a deletion of 86% of the CBP4 coding region. CBP4 protein is tightly associated with the mitochondrial membrane as evidenced by the association of the protein with the membrane fraction following carbonate extraction. The phenotype of cbp4 mutants is similar to that of cbp3 mutants. CBP3 encodes a second protein essential for ubiquinol-cytochrome c reductase activity. We found that loss of CBP3 protein does not affect the membrane stability or steady state concentration of CBP4 protein. A double mutant containing a deletion in both CBP3 and CBP4 was constructed. Our study shows that the phenotype of the double mutant is identical to the phenotypes of the individual single mutants.
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PMID:Characterization of CBP4, a new gene essential for the expression of ubiquinol-cytochrome c reductase in Saccharomyces cerevisiae. 806 53


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