title: Ferrocyanide as electron donor to cytochrome aa3. Cytochrome c requirement for oxygen uptake.
abstract: 1. In the absence of cytochrome c, ferrocyanide or ferrous sulphate reduces cytochrome c oxidase (EC 1.9.3.1), but no continuous oxygen uptake ensues, as it does with N,N,N',N'-tetramethyl-p-phenylenediamine or reduced phenazine methosulphate as reductants, unless a substoichiometric amount of cytochrome c or an excess of clupein is present. Cytochrome c cannot be replaced by porphyrin cytochrome c. 2. Cytochrome c, porphyrin cytochrome c and clupein all stimulate the reduction of cytochrome aa3 by ferrocyanide. 3. A model is proposed to explain these findings in which a high-affinity site for cytochrome c on the oxidase regulates the access of hydrophilic electron donors to a low-affinity site, and reduction via the high-affinity site is required for continuous oxygen uptake. 4. Furthermore, it is shown that upon reaction of oxidase with ferrocyanide, cyano-oxidase is formed.
mesh_terms: D003486:Cyanides; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005295:Ferrocyanides; D007700:Kinetics; D007773:Lactates; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011166:Porphyrins; D011485:Protein Binding; D011773:Pyruvates; D013053:Spectrophotometry
chemical_list: D003486:Cyanides; D003574:Cytochrome c Group; D005295:Ferrocyanides; D007773:Lactates; D011166:Porphyrins; D011773:Pyruvates; D003576:Electron Transport Complex IV