[44] Preparation and properties of reduced coenzyme Q-cytochrome c reductase (complex III of the respiratory chain)
1967; Academic Press; Linguagem: Inglês
10.1016/0076-6879(67)10047-5
ISSN1557-7988
Autores Tópico(s)Mitochondrial Function and Pathology
ResumoThis chapter describes the preparation and properties of reduced coenzyme Q-cytochrome c reductase (complex III of the respiratory chain). The rate of reduction of cytochrome c by reduced coenzyme Q2 is estimated from the amount of cytochrome c that is reduced (absorbency change at 550 mμ) in a sample of the assay mixture that has been allowed to react for 10 seconds. The enzyme-catalyzed reaction is stopped by the addition of an appropriate stop reagent. Three procedures for the preparation of (reduced coenzyme Q) cytochrome c reductase are described. All three procedures utilize the S-1 fraction of the procedure described for the preparation of DPNH cytochrome c reductase. The purification procedure described in the chapter utilizes the final supernatant solution obtained in the preparation of DPNH-cytochrome c reductase. (Reduced eoenzyme Q)-eytoehrome e reduetase can be stored as a solution in the Tris-suerose-histidine buffer for weeks at –20° with little loss in activity. The reduced forms of coenzyme Q1, eoenzyme Q2, and eoenzyme Q10 all serve as electron-donor substrates with complex III. (Reduced coenzyme Q)-cytochrome c reductase is inhibited almost completely by antimycin A at concentrations approaching the concentration of cytochrome cl in the solution of enzyme (1.5 μg per milligram of protein of complex III). In the assay system described, (reduced coenzyme Q)-cytochrome c reductase is active in the pH range from 6.0 to 8.5, with an optimal activity at pH 7.4.
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