Electron transfer copper oxidases

FIGURE 21.17 The electron transfer pathway for cytochrome oxidase. Cytochrome c binds on the cytosolic side, transferring electrons through the copper and heme centers to reduce O9 on the matrix side of the membrane. 

Cytochrome c oxidase contains two heme centers (cytochromes a and %) as well as two copper atoms (Figure 21.17). The copper sites, Cu and Cug, are associated with cytochromes a and respectively. The copper sites participate in electron transfer by cycling between the reduced (cuprous) Cu state and the oxidized (cupric) Cu state. (Remember, the cytochromes and copper sites are one-electron transfer agents.) Reduction of one oxygen molecule requires passage of four electrons through these carriers—one at a time (Figure... 

Cytochrome c oxidase contains two, or possibly three, copper atoms referred to as Cua and Cub since they do not fit into the usual classification. The former (possibly a dimer) is situated outside the mitochondrial membrane, whereas the latter is associated with an iron atom within the membrane. Both have electron transfer functions but details are as yet unclear. 

Blue copper electron transfer proteins, 6,712-717 Blue copper oxidases, 6,699 Blue copper proteins, 2, 557 6, 649 Blue electron transfer proteins, 6,649,652 spectroscopy, 6, 651 Blue oxidases copper, 6,654,655 Blueprint process, 6,124 Blue proteins model studies, 6,653 Boleite... 

Laccase, 6,699 copper, 6,654 cytochrome oxidases concerted electron transfer, 6,683 fungal... 

Copper 55 3 x 1(T3 Electron transfer, oxidases, oxygen transport... 

Fig. 6.9 The catalysts for denitrification. Nitrate is reduced by a molybdenum enzyme while nitrite and oxides of nitrogen are reduced today mainly by copper enzymes. However, there are alternatives, probably earlier iron enzymes. The electron transfer bct complex is common to that in oxidative phosphorylation and similar to the bf complex of photosynthesis, while cytochrome c2 is to be compared with cytochrome c of oxidative phosphorylation. These four processes are linked in energy capture via proton (H+) gradients see Figure 6.8(a) and (b) and the lower parts of Fig. 6.9 which show separately the active site of the all iron NO-reductase, and the active site of cytochrome oxidase (02 reductase).

Binding of anions, cations, and organic substrates. In order to probe the roles of the different types of copper atoms and the nature of the electron transfer pathways between them, a variety of complexes of hCP with inhibitors of oxidase activity and... 

Cytochrome c oxidase is a copper protein, which, in the respiratory electron-transfer chain of mitochondria and many bacteria, catalyses the reduction of molecular oxygen to water, according to the reaction ... 

Copper, Cu (d °), Cu " (d ) 3, trigonal planar A-Imidazole Electron transfer in Type III heme-copper oxidases (Cub in cytochrome c oxidase, for example)... 

Figure 1 also contains a drawing of the electronic structure of plastocy-anin (Penfield et al., 1981, 1985), oriented according to the first part of Fig. 1. The d-orbital plane appears to be normal to the peptide plane that is extended by the hydrogen-bonding pair the it orbital of the thiolate would then also be affected, poising the cluster for electron transfer and, interestingly, apparently in the direction utilized by the multi-copper protein ascorbate oxidase (see Section V,A).

Electron transfer (continued) intramolecular, from type-1 copper center to trinuclear copper center blue copper oxidases, 40 175-178 iron-sulfur proteins, 47 405, 474-479 kinetic model, flavocytochrome bj, 36 282-283... 

Ceruloplasmin is involved in copper storage and transport as well as in iron mobilisation and oxidation. Among the blue oxidases it is unique since it contains, in addition to the usual motif of a type 1 combined with the trinuclear cluster, two other type 1 coppers. Electron transfer occurs, however, only between five of the six copper ions since one of the type 1 centres is not catalytically relevant due to its too high redox potential. The redox potentials of the centres were determined and possible electron transfer pathways among the copper sites were discussed.101... 

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