The antioxidant functions of cytochrome c.
Low (C(1/2) = 1.5 x 10(-7) M) concentrations of horse cytochrome c strongly inhibit H(2)O(2) production by rat heart mitochondria under conditions of reverse electron transfer from succinate to NAD(+). The effect is abolished by binding of cytochrome c with liposomes and is not prevented by SOD. Yeast cytochrome c is much less effective than the horse protein whereas acetylated horse cytochrome c is without effect. H(2)O(2) formation stimulated by antimycin A is resistant to added cytochrome c. In inside-out submitochondrial vesicles, H(2)O(2) production is suppressed by all three cytochrome c samples tested, but at higher concentrations (C(1/2) is about 5 x 10(-7) M). In vesicles, SOD abolishes the cytochrome c inhibition. We conclude that extramitochondrial cytochrome c is competent in down-regulation of the Complex I H(2)O(2) production linked to the reverse electron transfer. Such an effect is absent in the inside-out submitochondrial vesicles where another antioxidant cytochrome c function can be observed, i.e. the oxidation of O(2-*) to O(2). A possible role of cytochrome c in the antioxidant defence is discussed.
Korshunov
S S
SS
Department of Bioenergetics, A.N. Belozersky Institute of Physico-Chemical Biology and International Lazer Centre, Moscow State University, Moscow, Russia.
Krasnikov
B F
BF
Pereverzev
M O
MO
Skulachev
V P
VP
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism*; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D008081:Liposomes; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D000975:Antioxidants; D003574:Cytochrome c Group; D008081:Liposomes; D017382:Reactive Oxygen Species; D000968:Antimycin A; D006861:Hydrogen Peroxide