The participation of coenzyme Q in free radical production and antioxidation

• Published in: Free Radical Biology and Medicine Vol. 8; no. 6; pp. 545 - 565
• Main Author: Beyer, Robert E.
• Format: Book Review Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 1990; Elsevier Science
• Subjects: Animals; Antioxidant; Antioxidants; Biological and medical sciences; Cell structures and functions; Coenzyme Q; DT diaphorase; Electron Transport - drug effects; Free Radicals; Fundamental and applied biological sciences. Psychology; Humans; Lipid peroxidation; Mitochondria - metabolism; Mitochondria and cell respiration; Molecular and cellular biology; Oxidation-Reduction - drug effects; Review; Superoxide dismutase; Ubiquinone; Ubiquinone - pharmacology; Free radicals; CoQH 2; CoQ; Lipid peroxidation; Coenzyme Q; DT diaphorase; Superoxide dismutase; SOD; Review; MDA; Antioxidant; TBA; Ubiquinone; SMPs; Mitochondria; Dihydrolipoamide reductase (NAD+); Electron transfer; Lipids; Oxidation; Coenzyme
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/0891-5849(90)90154-B

Published experimental data pertaining to the participation of coenzyme Q as a site of free radical formation in the mitochondrial electron transfer chain and the conditions required for free radical production have been reviewed critically. The evidence suggests that a component from each of the mitochondrial NADH-coenzyme Q, succinate-coenzyme Q, and coenzyme QH 2-cytochrome c reductases (complexes I, II, and III, most likely a nonheme iron-sulfur protein of each complex, is involved in free radical formation. Although the semiquinone form of coenzyme Q may be formed during electron transport, its unpaired electron most likely serves to aid in the dismutation of superoxide radicals instead of participating in free radical formation. Results of studies with electron transfer chain inhibitors make the conclusion dubious that coenzyme Q is a major free radical generator under normal physiological conditions but may be involved in superoxide radical formation during ischemia and subsequent reperfusion. Experiments at various levels of organization including subcellular systems, intact animals, and human subjects in theclinical setting, support the view that coenzyme Q, mainly in its reduced state, may act as an antioxidant protecting a number of cellular membranes from free radical damage.