Protonmotive stoichiometry of rat liver cytochrome c oxidase: determination by a new rate/pulse method.
The stoichoimetry of vectorial H+ ejection coupled to electron flow through the cytochrome c oxidase (EC 1.9.3.1) of rat liver mitochondria was determined by a new rate/pulse method. This is a modification of the oxygen-pulse method. Electron flow through the oxidase is initiated by adding oxygen to suspensions of anaerobic mitochondria at a known and constant rate. Cytochrome c oxidase was examined directly or in combination with cytochrome c reductase (ubiquinol:ferricytochrome c oxidoreductase). In both cases the----H0+/2e- ratio was found to be constant during the time-course of oxygen reduction, and thus independent of delta pH. The stoichiometries observed were consistent with mechanistic stoichiometries of 2 and 6 for cytochrome c oxidase alone and cytochrome c oxidase together with cytochrome c reductase, respectively. The stoichiometry of cytochrome c reductase alone was also examined, by using ferricyanide in place of oxygen. The results obtained were consistent with the accepted mechanistic stoichiometry of 4 for this enzyme.
Moody
A J
AJ
Glynn Research Institute, Bodmin, Cornwall, U.K.
Mitchell
R
R
West
I C
IC
Mitchell
P
P
D000818:Animals; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005292:Ferricyanides / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000201:enzymology; D009994:Osmolar Concentration; D010100:Oxygen / Q000378:metabolism; D011522:Protons; D051381:Rats; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
D005292:Ferricyanides; D011522:Protons; D014451:Ubiquinone; C007931:hexacyanoferrate III; D003576:Electron Transport Complex IV; C003741:ubiquinol; D010100:Oxygen