Ferrocyanide as electron donor to cytochrome aa3. Cytochrome c requirement for oxygen uptake |
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Authors: | K Krab EC Slater |
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Institution: | Laboratory of Biochemistry, B.C.P. Jansen Institute, University of Amsterdam, Plantage Muidergracht 12, 1018 TV Amsterdam The Netherlands |
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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. |
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Keywords: | Cytochrome c oxidase Cytochrome c Oxygen uptake Ferrocyanide Electron donor TMPD Mops morpholinopropane sulphonic acid |
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