Oxidation of nicotinamide coenzyme dimers by one-electron-accepting proteins.
The nicotinamide nucleotide dimers (NAD)2 and (NADP)2, obtained by electrochemical reduction of NAD+ and NADP+, are able to reduce such single-electron acceptors as the proteins cytochrome c, azurin and methaemoglobin, though at different rates. Under the same conditions the reduced nicotinamide coenzymes NADH and NADPH are not able to reduce these proteins at measurable rates unless a catalyst (phenazine methosulphate or NADH-cytochrome c reductase in the case of cytochrome) is present. The redox mechanism seems to involve the formation of an NAD(P). radical that in the presence of O2 gives rise to superoxide (O2.-), since superoxide dismutase inhibited these reactions.
D001400:Azurin / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D005609:Free Radicals; D046911:Macromolecular Substances; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D005609:Free Radicals; D046911:Macromolecular Substances; D009243:NAD; D001400:Azurin; D009249:NADP; D013482:Superoxide Dismutase; D010100:Oxygen