title: The oxidation of Pseudomonas cytochrome c-551 oxidase by potassium ferricyanide.
abstract: Stopped-flow kinetics were made of the reaction between ascorbate-reduced Pseudomonas cytochrome oxidase and potassium ferricyanide under both N2 and CO atmospheres. Under N2 three kinetic processes were observed, two being dependent on ferricyanide concentration, with second-order rate constants of 9.6 X 10(4)M-1.s-1 and 1.5 X 10(4)M-1.s-1, whereas the other was concentration-independent, with a first-order rate constant of 0.17 +/- 0.03s-1. Measurements of their kinetic difference spectra have allowed the fastest and second-fastest phases of the reaction to be assigned to direct bimolecular reactions of ferricyanide with the haem c and haem d, moieties of the enzyme respectively. Under CO, the second-order rate constant for the reaction of the haem c was, at 1.3 X 10(5)M-1.s-1, slightly enhanced over the rate in a N2 atmosphere, but the reaction velocity of the haem d1 component was greatly decreased, being apparently limited to that of the rates of CO dissociation from the molecule (0.15s-1 and 0.03s-1). The results are compared with those obtained during a previous study of the reaction of reduced Pseudomonas cytochrome oxidase with oxidized azurin.
mesh_terms: D002248:Carbon Monoxide / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005292:Ferricyanides / Q000378:metabolism*; D007700:Kinetics; D009584:Nitrogen; D010084:Oxidation-Reduction; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D013057:Spectrum Analysis
chemical_list: D005292:Ferricyanides; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV; D009584:Nitrogen