Cited by 1,214Mitochondrial Function and PathologyCoenzyme Q10 studies and effectsRedox biology and oxidative stress

Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria

Turrens, Julio F., Alexandre, Adolfo, Lehninger, Albert L.·1985·Archives of Biochemistry and Biophysics

Abstract

Much evidence indicates that superoxide is generated from O2 in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O2, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the H2O2-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of H2O2, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent H2O2 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of O2. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate- and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of O2. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing O2 to O2-.

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Crossref · 10.1016/0003-9861(85)90293-0

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  • The unpaired electron of ubisemiquinone is normally transferred to the cytochrome b center of complex III, but can also react with molecular oxygen to form superoxide.

    “Normally, the unpaired electron of ubisemiquinone is transferred to the cytochrome b center of complex III; however, this electron can also react with molecular oxygen to form superoxide 2, 26.”

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Authors
Turrens, J. F., Alexandre, A., & Lehninger, A. L.
Affiliations
University of Padua (IT)
Corresponding author
Lehninger, Albert L.
Venue
Archives of Biochemistry and Biophysics
Publisher
Elsevier BV
Published
1985-03
Volume
237
Issue
2
Pages
408-414
ISSN
0003-9861 (ISSN-L)
OpenAlex
W2060363769
Cited by
1,214
References
23
Citations by year
2026: 8 · 2025: 12 · 2024: 15 · 2023: 10 · 2022: 22 · 2021: 33 · 2020: 27 · 2019: 18 · 2018: 26 · 2017: 22 · 2016: 31 · 2015: 40 · 2014: 45 · 2013: 37 · 2012: 50
FWCI
2.88
Type
journal article
Language
en
Open access
closed
Locations
  • Archives of Biochemistry and Biophysics (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Cancer Institute (CA 25360)
  • National Institute of General Medical Sciences (GM05919)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Mitochondrial Function and Pathology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Coenzyme Q10 studies and effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Redox biology and oxidative stress
Keywords
ubisemiquinone, superoxide production, mitochondrial complex III, heart mitochondria, antimycin A, hydrogen peroxide production, myxothiazol, cytochrome c, cytochrome b, ubiquinol, Q-cycle, electron transfer to oxygen, superoxide dismutase
MeSH terms
Animals, Antimycin A, Coenzymes, Cytochrome b Group, Cytochrome c Group, Electron Transport, Hydrogen Peroxide, Methacrylates, Mitochondria, Heart, Multienzyme Complexes, NADH, NADPH Oxidoreductases, Oxygen Consumption, Quinone Reductases, Succinates, Superoxides, Thiazoles, Electron Transport Complex III, Ubiquinone, Rats, In Vitro Techniques

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