The restoration of DPNH oxidase activity by coenzyme Q (ubiquinone)

Szarkowska, L

doi:10.1016/0003-9861(66)90228-1

Cited by 161 publications

(31 citation statements)

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“…NADH oxidase could not be restored in these preparations. To overcome any possible acetone inactivation of NADH oxidase, pentane was subsequently employed to extract ubiquinone from lyophilized membranes [2]. Using this technique it was clearly demonstrated that ubiquinone is required for both succinate oxidase and NADH oxidase [2,3].…”

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confidence: 99%

“…The original methods developed for the incorporation of Q into solvent-extracted membranes involved additions of alcoholic solutions of Q directly to particles suspended in buffer [1,2,7]. Though this method can be effectively used for reactivation of NADH oxidase and succinate oxidase, the concentrations of Q required for complete activation far exceed those normally present in the membrane.…”

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Studies with Ubiquinone‐Depleted Submitochondrial Particles

Norling

et al. 1974

European Journal of Biochemistry

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1 . The incorporation of small amounts of ubiquinone (Q) into pentane-extracted submitochondrial particles has been studied. A procedure is described which allows nearly quantitative incorporation of as little as 0.2 to 0.3 nmol Q/mg protein, i.e: less than 10 % of the Q present in the lyophilized particles prior to extraction.2. It is shown that both NADH oxidase and succinate oxidase activities can be restored to 100 % of that in lyophilized particles by incorporation of 6 -8 nmol Q/mg protein. The relative activities of both oxidases show a parallel response to an increase of the Q content of the particles between 0.2 and 22 nmol Q/mg protein, 50 % reactivation being obtained at about 2 nmol Q/mg protein.3. 50 to 60% of the incorporated Q can be reduced by NADH or succinate, independent of the total concentration of Q in the membrane. Similar reduction values were obtained for lyophilized particles prior to extraction, suggesting that incorporated Q functions similarly to that originally present in the particles.4. Succinate dehydrogenase activity, which is decreased 50% by extraction of Q, can be completely restored upon incorporation of only 1.5 nmol Q/mg protein.5. Extraction of lyophilized particles with pentane + 10% acetone results in a more effective removal of Q, but also in a differential Q requirement for NADH oxidase and succinate oxidase.Thin-layer chromatography shows that extraction with pentane + acetone removes an additional, unidentified, nonpolar lipid.6. The present data do not support the belief that succinate oxidase and NADH oxidase communicate with separate pools of Q. Ubiquinone (Q) was first established as an obligate member of the electron transport chain by experiments in which succinate oxidase activity was decreased by acetone extraction, and then restored by incorporation of ubiquinone [l]. NADH oxidase could not be restored in these preparations. To overcome any possible acetone inactivation of NADH oxidase, pentane was subsequently employed to extract ubiquinone from lyophilized membranes [2]. Using this technique it was clearly demonstrated that ubiquinone is required for both succinate oxidase and NADH oxidase [2,3].In spite of these advances, the position and function of Q in the electron transport sequence are still Abbreviation. Q, ubiquinone-50 or coenzyme Qlo. Enzlvne. Succinate dehydrogenase (E.C. 1.3.99.1).___ . -not entirely clear. Kroger and Klingenberg [4,5] suggested that the Q pool in mitochondria is mobile, and, as such, interacts freely with both the succinate and NADH dehydrogenases. In this scheme Q acts as a general reservoir for protons and electrons at that point where the dehydrogenases converge with cytochrome b. On the other hand, experiments showing that NADH oxidase has more specific structural requirements for Q [6], and that more Q is needed for complete reactivation of NADH oxidase than for succinoxidase [4,7], have led Gutman et al. [7] to conclude that different fixed pools of Q are associated with the two primary dehydrogenases.In addition to fun...

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Studies with Ubiquinone‐Depleted Submitochondrial Particles

Norling

et al. 1974

European Journal of Biochemistry

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“…The data ( (11). Pentane was used for ex- Although CoQio was more effective than CoQ7 on a molar basis in preventing inhibition, a higher molar ratio of CoQ7 to adriamycin was as effective as CoQio.…”

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confidence: 99%

Bioenergetics in clinical medicine: prevention by forms of coenzyme Q of the inhibition by adriamycin of coenzyme Q10-enzymes in mitochondria of the myocardium.

Kishi¹,

Watanabe²,

Folkers³

1976

Proc. Natl. Acad. Sci. U.S.A.

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Adriamycin inhibits the succinoxidase system and the NADH-oxidase system. Both of the intact mitochondrial enzymes and the pentane-extracted preparations are inhibited. The inhibition can be prevented by a molar ratio of coenzyme to adriamycin of 3:1 for coenzyme QIo (ubiquinone) Adriamycin and related anthracyclines are now widely used in clinical medicine for the chemotherapy of cancer (1). Carter and Blum (2) summarized the wide range of clinical antitumor activities and the integration of adriamycin into combined modality protocols. The clinical use of adriamycin is accompanied by serious side-effects, which rigidly restrict its use. Although cardiotoxicity is the most serious side-effect in cancer patients, there is a spectrum of other major side-effects, including hematologic toxicity. The biochemical elucidation of the mechanism (3) of these side-effects, particularly the cardiotoxicity, has become urgent, and particularly if such knowledge could minimize side-effects.We have considered that the cardiotoxicity of adriamycin might be due to inhibition of coenzyme Q1o-enzymes. Data have now been obtained on four forms of coenzyme Q (CoQ) that show that the coenzymes prevent this inhibition in vitro. The biochemical basis of this study of cardiotoxicity is the knowledge that coenzyme Qio (ubiquinone) is an indispensable component of the succinoxidase and the NADH-oxidase systems and other CoQi0-enzymes which are essential to the electron transfer mechanism and oxidative phosphorylation ("bioenergetics") of mitochondria of the human myocardium. Inhibition (toxicity) of enzymes of respiration could be damaging to the heart, and could range from a minor to a major component of the cardiotoxicity of adriamycin. METHODS The methods for these assays with adriamycin, the two aglycones, and the four forms of coenzyme Q have been reported (4). Preparation of beef heart mitochondria (5) and extraction with pentane (6) were described. The determination of the specific activities of succinoxidase and NADH-oxidase, inhi-

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“…Lyophilized ETP were mechanically homogenized with pentane (Szarkowska, 1966). Where the distribution of quinone was investigated the 15 S and 105s fractions were assayed.…”

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