Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q16795 (ubiquinone)
 5,455 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An NADH dehydrogenase possessing a specific activity 3-5 times that of membrane-bound enzyme was obtained by extraction of Acholeplasma laidlawii membranes with 9.0% ethanol at 43 degrees C. This dehydrogenase contained only trace amounts of iron (suggesting an uncoupled respiration), a flavin ratio of 1:2 FAD to FMN and 30-40% lipid. Its resistance to sedimentation is probably due to the high flotation density of the lipids. It efficiently utilized ferricyanide, menadione and dichlorophenol indophenol as electron acceptors, but not O2, ubiquinone Q10 or cytochrome c. Lineweaver-Burk plots of the dehydrogenase were altered to linear functions upon extraction with 9.0% ethanol. A secondary site of ferricyanide reduction could not be explained by the presence of cytochromes, which these membranes lack. In comparison to other respiratory chain-linked NADH dehydrogenases in cytochrome-containing respiratory chains, this dehydrogenase was characterized by similar Km's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, but considerably smaller V's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, and smaller specific activities. It was not stimulated or reactivated by the addition of FAD, FMN, Mg2+, cysteine or membrane lipids, and was less sensitive to respiratory inhibitors than unextracted enzyme. The ineffectiveness of ADP stimulation on O2 uptake, the insensitivity to oligomycin and the very low iron content of A. laidlawii membranes were considered in relation to conservation of energy by these cells. Some kinetic properties of the dehydrogenation, the uniquely high glycolipid content and apparently uncoupled respiration at Site I were noteworthy characteristics of this NADH dehydrogenase from the truncated respiratory chain of A. laidlawii.
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PMID:The reduced nicotinamide adenine dinucleotide "oxidase" of Acholeplasma laidlawii membranes. 17 76

A lipid fraction from Escherichia coli was extracted with apolar solvents and was found to protect mice from a number of experimental bacterial infections. The benzoquinone, ubiquinone-8, was isolated from this extract by high pressure liquid chromatography and identified as such by nuclear magnetic resonance and mass spectrometry. At a dose of 25 mg/kg this substance was found to provide complete protection against otherwise lethal infections with gram-negative and gram-positive bacteria in mice. Treatment was most effective when given intravenously 24 h before infection. In comparative studies, ubiquinone-8 had a clearly higher activity than ubiquinones-4, Q6, and Q10. A highly significant increase in the clearance rate of bacteria from the blood by the spleen and the liver of treated animals, correlated well with the protective effect of ubiquinone-8. The compound stimulated the ability of mouse macrophages to incorporate sheep erythrocytes and significantly increased the number of antibody-producing cells in spleens of mice.
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PMID:Nonspecific resistance to bacterial infections. Enhancement by ubiquinone-8. 36 71

The hyperthermophilic archaebacterium Pyrodictium brockii grows optimally at 105 degrees C by a form of metabolism known as hydrogen-sulfur autotrophy, which is characterized by the oxidation of H2 by S0 to produce ATP and H2S. UV-irradiated membranes were not able to carry out the hydrogen-dependent reduction of sulfur. However, the activity could be restored by the addition of ubiquinone Q10 or ubiquinone Q6 to the UV-damaged membranes. A quinone with thin-layer chromatography migration properties similar to those of Q6 was purified by thin-layer chromatography from membranes of P. brockii, but nuclear magnetic resonance analysis failed to confirm its identity as a ubiquinone. P. brockii quinone was capable of restoring hydrogen-dependent sulfur reduction to UV-irradiated membranes. Hydrogen-reduced-minus-air-oxidized absorption difference spectra on membranes revealed absorption peaks characteristic of c-type cytochromes. A c-type cytochrome with alpha, beta, and gamma peaks at 553, 522, and 421 nm, respectively, was solubilized from membranes with 0.5% Triton X-100. Pyridine ferrohemochrome spectra confirmed its identity as a c-type cytochrome, and heme staining of membranes loaded on sodium dodecyl sulfate gels revealed a single heme-containing component of 13 to 14 kDa. Studies with the ubiquinone analog 2-n-heptyl-4-hydroxyquinoline-N-oxide demonstrated that the P. brockii quinone is located on the substrate side of the electron transport chain with respect to the c-type cytochrome. These first characterizations of the strictly anaerobic, presumably primitive P. brockii electron transport chain suggest that the hydrogenase operates at a relatively high redox potential and that the H2-oxidizing chain more closely resembles those of aerobic eubacterial H2-oxidizing bacteria than those of the H2-metabolizing systems of anaerobes or the hyperthermophile Pyrococcus furiosus.
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PMID:Hydrogen-oxidizing electron transport components in the hyperthermophilic archaebacterium Pyrodictium brockii. 130 14

The electron transfer from ubiquinol-2 to ferricytochrome c mediated by ubiquinol:cytochrome c oxidoreductase [E.C. 1.10.2.2] purified from beef heart mitochondria, which contained one equivalent of ubiquinone-10 (Q10), was investigated under initial steady-state conditions. The Q10-depleted enzyme was as active as the Q10-containing one. Double reciprocal plots for the initial steady-state rate versus one of the two substrates at various fixed levels of the other substrate gave parallel straight lines in the absence of any product. Intersecting straight lines were obtained in the presence of a constant level of one of the products, ferrocytochrome c. The other product, ubiquinone-2, did not show any significant effect on the enzymic reaction. Ferrocytochrome c non-competitively inhibited the enzymic reaction against either ubiquinol-2 or ferricytochrome c. These results indicate a Hexa-Uni ping-pong mechanism with one ubiquinol-2 and two ferricytochrome c molecules as the substrates, which involves the irreversible release of ubiquinone-2 as the first product and the irreversible isomerization between the release of the first ferrocytochrome c and the binding of the second ferricytochrome c. Considering the cyclic electron transfer reaction mechanism, this scheme suggests that the binding of quinone or quinol to the enzyme and electron transfer between the iron-sulfur center and cytochrome c1 are rigorously controlled by the electron distribution within the enzyme.
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PMID:Kinetic mechanism of beef heart ubiquinol:cytochrome c oxidoreductase. 131 82

The localization of ubiquinone has been investigated in phospholipid bilayer vesicles in studies of fluorescence quenching of membrane-bound probes by ubiquinone homologs (Qn, where n is the number of the isoprenoid units of the chain). Fluorescence-quenching data obtained by using a set of anthroylstearate probes, having the fluorophore located at different depths, revealed that ubiquinone-3 is located throughout the whole bilayer thickness. From the bimolecular quenching constants in the membrane, lateral diffusion coefficients in two dimensions were calculated to span values of 10(-7)-10(-6) cm2.s-1. This suggests that ubiquinones laterally diffuse in a very fluid environment. On this basis, it is proposed that their translational diffusion in the bilayer takes place in two dimensions, with the quinone ring oscillating between the two bilayer surfaces within a hydrophobic environment not extending beyond the glycerol region. This model implies that the quinonic head is both settled near the polar surface of the bilayer and buried into the host hydrocarbon interior. This two-site distribution was confirmed for all Qn, except Q0, by their linear dichroism spectra in the bilayers provided by disc-like lyotropic nematic liquid crystals. These spectra also provided detailed information on the preferential orientations of the quinonic head of the different derivatives within the two sites. The mechanism by which the localization and orientation of Qn guest molecules inside the host bilayer is modulated by the isoprenoid chain length is discussed on a thermodynamical basis. Being that Qn is expected to be also widely contained in the highly curved cristae of the mitochondrial inner membrane, by using rod-like lyotropic nematic liquid crystals we searched out effects of the curvature of the host bilayer on those Qn distributions. The linear dichroism measurements reveal that Qn guest molecules are no longer obliged to find a partition between two different types of localizations when the host bilayer is highly curved. In this case all Qn, even the longest Q10, were found to stay parallel to the amphiphilic chains with a single site localization of the head near the polar interface. By the same linear dichroism technique, the local ordering of all Qn derivatives was also evaluated. The order parameters were found to be basically the same for all derivatives. This result is justified on the basis of the relaxation, caused by the surface curvature, of the lateral compression of the host chains.
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PMID:Localization and preferred orientations of ubiquinone homologs in model bilayers. 144 17

The in vitro toxicity of multiple hydrophobic compounds was the focus of this study. A mitochondrial respiratory assay, sensitive to perturbations caused by hydrophobic chemicals, was utilized to measure the effects of individual aromatic hydrocarbon pollutants and their mixtures on mitochondrial respiratory function. Benzene, naphthalene, acenaphthene, and 1-chloronaphthalene, common industrial solvents shown to interact additively in vivo, were evaluated using this in vitro assay system. Mitochondrial respiration was inhibited 50% (EC50) by 525 ppm (6.7 mM) benzene, 15 ppm (117 microM) naphthalene, 3.9 ppm (25.5 microM) acenaphthene, or 3.8 ppm (23.4 microM) 1-chloronaphthalene. NADH:O2 oxidoreductase (NADH-->O2), NADH:ubiquinone oxidoreductase, and ubiquinol:O2 oxidoreductase activities were inhibited by all four compounds, whereas succinate:O2 oxidoreductase, cytochrome c oxidase, and duroquinol:O2 oxidoreductase activities were not inhibited. Inhibition of mitochondrial respiration occurred at the level of ubiquinone (coenzyme Q10) for all four aromatic hydrocarbons. The ultraviolet absorbance spectrum of isolated Q10 was also altered by naphthalene, acenaphthene, or 1-chloronaphthalene, suggesting a specific interaction between that component of the respiratory chain and these aromatic hydrocarbons. Inhibition by a mixture of 2, 3, or 4 of the compounds tested was additive, reflecting a summation effect of each compound present in the mixture. This additive nature is consistent with previously reported effects of these compounds in vivo and with compounds having similar modes of action. The similar mode of action in vitro is a specific interaction with coenzyme Q10, not a generalized membrane perturbation as speculated to occur in vivo, and is the likely mechanism for the observed additive toxicity.
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PMID:Additive effects and potential inhibitory mechanism of some common aromatic pollutants on in vitro mitochondrial respiration. 147 93

Based on the partial nucleotide sequence analysis of 16S ribosomal ribonucleic acid (rRNA), presence of unique sphingoglycolipids in cellular lipid, and the major type of ubiquinone (Q10), we propose Sphingomonas gen. nov. with the type species Sphingomonas paucimobilis (Holmes et al, 1977) comb. nov. From the homology values of deoxyribonucleic acid-deoxyribonucleic acid hybridization and the phenotypic characteristics, three new species, Sphingomonas parapaucimobilis, Sphingomonas yanoikuyae, Sphingomonas adhaesiva, and one new combination, Sphingomonas capsulata, are described. S. parapaucimobilis JCM 7510 (= GIFU 11387), S. yanoikuyae JCM 7371 (= GIFU 9882), and S. adhaesiva JCM 7370 (= GIFU 11458) are designated as the type strains of the three new species. Emended description of the type strain of S. capsulata is presented.
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PMID:Proposals of Sphingomonas paucimobilis gen. nov. and comb. nov., Sphingomonas parapaucimobilis sp. nov., Sphingomonas yanoikuyae sp. nov., Sphingomonas adhaesiva sp. nov., Sphingomonas capsulata comb. nov., and two genospecies of the genus Sphingomonas. 211 72

Co-enzyme Q10 (ubiquinone) is a naturally occurring substance which has properties potentially beneficial for preventing cellular damage during myocardial ischemia and reperfusion. It plays a role in oxidative phosphorylation and has membrane stabilizing activity. The substance has been used in oral form to treat various cardiovascular disorders including angina pectoris, hypertension, and congestive heart failure. Its clinical importance is now being established in clinical trails worldwide.
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PMID:Co-enzyme Q10: a new drug for cardiovascular disease. 220 52

Ubiquinones (CoQn) are intrinsic lipid components of many membranes. Besides their role in electron-transfer reactions they may act as free radical scavengers, yet their antioxidant function has received relatively little study. The efficiency of ubiquinols of varying isoprenoid chain length (from Q0 to Q10) in preventing (Fe2+ + ascorbate)-dependent or (Fe2+ + NADPH)-dependent lipid peroxidation was investigated in rat liver microsomes and brain synaptosomes and mitochondria. Ubiquinols, the reduced forms of CoQn, possess much greater antioxidant activity than the oxidized ubiquinone forms. In homogenous solution the radical scavenging activity of ubiquinol homologues does not depend on the length of their isoprenoid chain. However in membranes ubiquinols with short isoprenoid chains (Q1-Q4) are much more potent inhibitors of lipid peroxidation than the longer chain homologues (Q5-Q10). It is found that: i) the inhibitory action, that is, antioxidant efficiency of short-chain ubiquinols decreases in order Q1 greater than Q2 greater than Q3 greater than Q4; ii) the antioxidant efficiency of long-chain ubiquinols is only slightly dependent on their concentrations in the order Q5 greater than Q6 greater than Q7 greater than Q8 greater than Q9 greater than Q10 and iii) the antioxidant efficiency of Q0 is markedly less than that of other homologues. Interaction of ubiquinols with oxygen radicals was followed by their effects on luminol-activated chemiluminescence. Ubiquinols Q1-Q4 at 0.1 mM completely inhibit the luminol-activated NADPH-dependent chemiluminescent response of microsomes, while homologues Q6-Q10 exert no effect. In contrast to ubiquinol Q10 (ubiquinone Q10) ubiquinone Q1 synergistically enhances NADPH-dependent regeneration of endogenous vitamin E in microsomes thus providing for higher antioxidant protection against lipid peroxidation. The differences in the antioxidant potency of ubiquinols in membranes are suggested to result from differences in partitioning into membranes, intramembrane mobility and non-uniform distribution of ubiquinols resulting in differing efficiency of interaction with oxygen and lipid radicals as well as different efficiency of ubiquinols in regeneration of endogenous vitamin E.
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PMID:Antioxidant action of ubiquinol homologues with different isoprenoid chain length in biomembranes. 222 28

During an epidemiologic survey, an unidentified strain of Legionella was isolated from water of a thermal spa in France. The strain (Lyon 8420412) had the cultural and biochemical characteristics typical of the genus Legionella. In direct immunofluorescence tests, the strain reacted weakly with fluorescein-conjugated antisera prepared against L. bozemanii serogroups 1 and 2, L. longbeachae serogroups 1 and 2 and L. anisa, and failed to react with sera prepared against 36 other species or serogroups. A fluorescein-conjugated antiserum prepared against strain Lyon 8420412 reacted strongly with the homologous strain and only weakly with the above-mentioned species. The cell-wall fatty acid profile, with a predominance of hexadecenoic (16:1) and hexadecanoic (16:0) acids, ubiquinone Q10 as the major quinone and a characteristic protein electrophoresis profile suggested that the isolate was different from other Legionella species. In DNA-DNA hybridization experiments, the strain was distinct from all named Legionella species, and from all unnamed species currently under study at the Centers for Disease Control. The name Legionella gratiana is proposed for the new species (type strain Lyon 8420412; CDC 1242). A serologic survey of antibodies reacting against L. gratiana indicated that personnel or patients at the spa therapy centre where the organism was isolated had higher antibody titres than a control population.
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PMID:Legionella gratiana sp. nov. isolated from French spa water. 269 60


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