Kinetics of cytochrome b reduction in submitochondrial particles.
(1) In agreement with Eisenbach and Gutman (Eisenbach, M. and Gutman, M. (1975) Eur. J. Biochem. 52, 107--116) the reduction of cytochrome b in beef-heart submitochondrial particles by succinate in the presence of antimycin was found to be biphasic, the relative amounts of fast and slow phases being dependent on the redox state of a compound located on the oxygen side of the antimycin block. (2) HQNO is a concentration sufficiently large to saturate the specific antimycin- and HQNO-binding sites can substitute for antimycin in these experiments. (3) The rate of the slow phase of the reduction of cytochrome b is decreased under anaerobic conditions and after pretreatment with 2,3-dimercaptopropanol (BAL). (4) In the presence of antimycin and cyanide, cytochrome b-562 is, to some extent, preferentially reduced in the rapid phase and b-566 in the slow phase. (5) The previously proposed regulatory effects of redox-sensitive components X and Y on the redox level and reduction kinetics, respectively, of cytochrome b are ascribed to the role of the Fe-S protein, when it is oxidized, in producing the reductant of cytochrome b by oxidation of QH2, and by the fact that when QH2 is bound to it, the reduced Fe-S protein cannot be oxidized by its natural oxidant, cytochrome c.
D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D002417:Cattle; D003573:Cytochrome b Group; D003580:Cytochromes / Q000378:metabolism*; D006912:Hydroxyquinolines / Q000494:pharmacology; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism; D010084:Oxidation-Reduction; D011190:Potassium Cyanide / Q000494:pharmacology; D013053:Spectrophotometry; D013367:Submitochondrial Particles / Q000378:metabolism*; D013772:Tetramethylphenylenediamine / Q000494:pharmacology
D003573:Cytochrome b Group; D003580:Cytochromes; D006912:Hydroxyquinolines; C001333:2-(n-heptyl)-4-hydroxyquinoline N-oxide; D000968:Antimycin A; D011190:Potassium Cyanide; D013772:Tetramethylphenylenediamine