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Bironaite DA, Cenas NK, Anusevicius ZJ, Medentsev AG, Akimenko VK, Usanov SA: Fungal quinone pigments as oxidizers and inhibitors of mitochondrial NADH:ubiquinone reductase. Arch Biochem Biophys. 1992 Sep;297(2):253-7.
The interaction of fungal quinone pigments bostricoidin, fusarubin, javanicin, and 2-oxyjuglone with mitochondrial NADH:ubiquinone reductase (complex I, EC 1.6.99.3) has been studied. The bimolecular rate constants (turnover number (TN)/Km) of rotenone-insensitive reduction of these compounds are in the range of 1.2 x 10 (4)-1.6 x 10 (5) M-1s-1. 2-Oxyjuglone acts as inhibitor of NADH:ferricyanide reductase reaction of complex I (KI = 30 microM). All quinone pigments, except javanicin, decrease the TN of reduction of 5,8-dioxy-1,4-naphtoquinone being reduced at its binding site but with significantly lower TN. They do not affect the rotenone-sensitive reduction of ubiquinone-1. The binding of quinone pigments close to the NADH and ferricyanide binding site is suggested. It seems that quinone pigments, especially 2-oxyjuglone, react with complex I faster than it follows from their approximate values of one-electron reduction potential calculated from their reactivities with flavocychrome b2 and adrenodoxin. |
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