Home
Resources
Publications
Generation of Superoxide Anion by Succinate-Cytochrome C Reductase From Bovine Heart Mitochondria

Generation of Superoxide Anion by Succinate-Cytochrome C Reductase From Bovine Heart Mitochondria

L Zhang, L Yu, C A Yu

J Biol Chem. 1998 Dec 18;273(51):33972-6.

PMID: 9852050

Abstract:

Production of superoxide anion (O-2), measured as the chemiluminescence of the 2-methyl-6-(p-methoxyphenyl)-3, 7-dihydroimidazo[1,2-a]pyrazin-3-one hydrochloride (MCLA)-O-2 adduct, was observed during electron transfer from succinate to cytochrome c by reconstituted succinate-cytochrome c reductase-phospholipid vesicles replenished with succinate dehydrogenase. Addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone or detergent to the reconstituted reductase-phospholipid vesicles abolished O-2 production, suggesting that O-2 generation is caused by the membrane potential generated during electron transfer through the cytochrome bc1 complex. Production of O-2 was also observed during electron transfer from succinate to cytochrome c by antimycin-treated reductase, in which approximately 99.7% of the reductase activity was inhibited. The rate of O-2 production was closely related to the rate of antimycin-insensitive cytochrome c reduction. Factors affecting antimycin-insensitive reduction of cytochrome c also affected O-2 production and vice versa. When the oxygen concentration in the system was decreased, the rate of O-2 production and cytochrome c reduction by antimycin-treated reductase decreased. When the concentrations of MCLA and cytochrome c were increased, the rate of O-2 production and cytochrome c reduction by antimycin-treated reductase increased. The rate of antimycin-insensitive cytochrome c reduction was sensitive to Qo site inhibitors such as 5-undecyl-6-hydroxy-4,7-dioxobenzothiazole. These results indicate that generation of O-2 during the oxidation of ubiquinol by the cytochrome bc1 complex results from a leakage of the second electron of ubiquinol from its Q cycle electron transfer pathway to interact with oxygen. The electron-leaking site is located at the reduced cytochrome b566 or ubisemiquinone of the Qo site because addition of MCLA to antimycin-treated cytochrome bc1 complex, in the presence of catalytic amounts of succinate-cytochrome c reductase, delayed cytochrome b reduction by succinate. In the presence of oxidized cytochrome c, purified succinate dehydrogenase also catalyzed oxidation of succinate to generate O-2. When succinate dehydrogenase was reconstituted with the bc1 particles to form succinate-cytochrome c reductase, the production of O-2 diminished. These results suggest that reduced FAD of succinate dehydrogenase is the electron donor for oxygen to produce O-2 in the absence of their immediate electron acceptor and in the presence of cytochrome c.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP9007436	Cytochrome c from bovine heart		9007-43-6	Price

As a specialist in analytical chemical Products, Alfa Chemistry offers consumers a wealth of raw materials and a full range of technologies and services.

QUICK LINKS

HEADQUARTERS

Tel:

Fax:

Email: