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The mitochondrial site of superoxide formation
Biochemical and Biophysical Research Communications
|July 31, 1986
Summary
Mitochondrial oxygen formation is linked to cytochrome b566, not ubiquinone, as electron transfer to oxygen requires proton availability. This study investigates electron transfer pathways in mitochondria.
Area of Science:
- Biochemistry
- Mitochondrial Physiology
- Electron Transport
Background:
- Ubiquinone and cytochrome b566 are implicated in mitochondrial oxygen formation via autoxidation.
- Their roles in electron transfer to oxygen outside the normal respiratory pathway require clarification.
Purpose of the Study:
- To evaluate the capacity of ubiquinone and cytochrome b566 to transfer electrons to molecular oxygen.
- To determine the conditions influencing out-of-sequence electron transfer in mitochondria.
Main Methods:
- Investigated electron transfer from reduced ubiquinone and cytochrome b566 to molecular oxygen.
- Assessed the impact of proton availability on ubiquinone's autoxidation.
- Correlated cytochrome b566 potential with oxygen release from mitochondria.
Main Results:
- Electron transfer from ubisemiquinone to oxygen is proton-dependent.
- Ubiquinone autoxidation was not observed in the mitochondrial membrane's aprotic environment.
- Mitochondrial O2 release correlated with low-potential cytochrome b566.
- Shifting cytochrome b566 to more positive potentials inhibited univalent electron transfer to oxygen.
Conclusions:
- Cytochrome b566 likely plays a role in mitochondrial oxygen formation.
- Ubiquinone's contribution is improbable under conditions lacking proton penetration.