Cytochrome c-cytochrome oxidase interaction at subzero temperatures.
Cytochrome oxidase forms two distinctive compounds with oxygen at --105 and --90 degrees C, one appears to be oxycytochrome oxidase (Compound A) and the other peroxycytochrome oxidase (Compound B). The functional role of compound B in the oxidation of cytochrome c has been examined in a variety of mitochondrial preparations. The rate and the extent of the reaction have been found to be dependent upon the presence of a fluid phase in the vicinity of the site of the reaction of cytochrome c and cytochrome oxidase. The kinetics of cytochrome c oxidation and of the slowly reacting component of cytochrome oxidase are found to be linked to one another even in cytochrome c depleted preparations, but under appropriate conditions, especially low temperatures, the oxidation of cytochrome c precedes that of this component of cytochrome oxidase. Based upon the identification of the slowly reacting components of cytochrome oxidase with cytochrome c, various mechanisms are considered which allow cytochrome c to be oxidized without the intervention of cytochrome a at very low temperatures, and tunneling seems an appropriate mechanism.
D000818:Animals; D002417:Cattle; D010856:Columbidae; D003574:Cytochrome c Group / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005615:Freezing; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008929:Mitochondria, Heart / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D008931:Mitochondria, Muscle / Q000201:enzymology; D010084:Oxidation-Reduction; D011485:Protein Binding; D051381:Rats
D003574:Cytochrome c Group; D003576:Electron Transport Complex IV