Superoxide radical formation by pure complex I (NADH : Ubiquinone oxidoreductase) from Yarrowia lipolytica

Alexander Galkin, U. Brandt

Research output: Contribution to journalArticlepeer-review

144 Citations (Scopus)


Generation of reactive oxygen species (ROS) is increasingly recognized as an important cellular process involved in numerous physiological and pathophysiological processes. Complex I ( NADH: ubiquinone oxidoreductase) is considered as one of the major sources of ROS within mitochondria. Yet, the exact site and mechanism of superoxide production by this large membrane-bound multiprotein complex has remained controversial. Here we show that isolated complex 1 from Yarrowia lipolytica forms superoxide at a rate of 0.15% of the rate measured for catalytic turnover. Superoxide production is not inhibited by ubiquinone analogous inhibitors. Because mutant complex I lacking a detectable iron-sulfur cluster N2 exhibited the same rate of ROS production, this terminal redox center could be excluded as a source of electrons. From the effect of different ubiquinone derivatives and pH on this side reaction of complex I we concluded that oxygen accepts electrons from FMNH2 or FMN semiquinone either directly or via more hydrophilic ubiquinone derivatives.
Original languageEnglish
Pages (from-to)30129-30135
Number of pages7
JournalJournal of Biological Chemistry
Issue number34
Publication statusPublished - 26 Aug 2005

ASJC Scopus subject areas

  • Biochemistry


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