Volume 552, Issue 2 p. 335-344
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Mitochondrial formation of reactive oxygen species

Julio F. Turrens

Corresponding Author

Julio F. Turrens

Department of Biomedical Sciences, University of South Alabama, Mobile, AL 36688, USA

Corresponding author J. F. Turrens: Biomedical Sciences UCOM 6000, University of South Alabama, Mobile, AL 36688-0002, USA. Email: [email protected]Search for more papers by this author
First published: 01 October 2003
Citations: 2,445


The reduction of oxygen to water proceeds via one electron at a time. In the mitochondrial respiratory chain, Complex IV (cytochrome oxidase) retains all partially reduced intermediates until full reduction is achieved. Other redox centres in the electron transport chain, however, may leak electrons to oxygen, partially reducing this molecule to superoxide anion (O2•). Even though O2• is not a strong oxidant, it is a precursor of most other reactive oxygen species, and it also becomes involved in the propagation of oxidative chain reactions. Despite the presence of various antioxidant defences, the mitochondrion appears to be the main intracellular source of these oxidants. This review describes the main mitochondrial sources of reactive species and the antioxidant defences that evolved to prevent oxidative damage in all the mitochondrial compartments. We also discuss various physiological and pathological scenarios resulting from an increased steady state concentration of mitochondrial oxidants.