Characterization of NAD(P)H-dependent ubiquinone reductase activities in rat liver microsomes

Tsuyoshi Shigemura, Dongchon Kang, Kazue Nagata-Kuno, Koichiro Takeshige, Naotaka Hamasaki

研究成果: Contribution to journalArticle査読

10 被引用数 (Scopus)


Exogenous ubiquinone-10 was efficiently reduced by rat liver microsomes in the presence of NADH and NADPH under anaerobic conditions. Ubiquinone-10 reduced under anaerobic conditions was rapidly re-oxidized by the re-aeration. The reduction and re-oxidation were not observed when the reactions were carried out with the boiled microsomes or without microsomes, suggesting that the reactions were enzymatically catalyzed by the electron transport system(s) from NAD(P)H to O2 through the ubiquinone. The Km and Vmax of the reductase activity for NADH were 0.4 mM and 1.7 nmol/min per mg of protein, and those for NADPH were 19 μM and 2.1 nmol/min per mg of protein, respectively. The NADH-dependent oxidoreduction system was different from the NADPH-dependent system because of the following observations; (1) rotenone inhibited only the NADH-dependent ubiquinone-10 reductase, (2) dicoumarol inhibited the NADPH-dependent ubiquinone-10 reduction more potently than the NADH-dependent reduction and (3) the activity oxidizing the reduced ubiquinone-10 in the presence of NADH was less than that in the presence of NADPH. Endogenous ubiquinone-9 was also reduced and re-oxidized in essentially the same manner as exogenous ubiquinone-10. Thus, ubiquinone-10 oxidoreductase in rat liver microsomes acts on endogenous ubiquinone-9.

ジャーナルBBA - Bioenergetics
出版ステータス出版済み - 3 1 1993

All Science Journal Classification (ASJC) codes

  • 生物理学
  • 生化学
  • 細胞生物学


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