Ionic strength dependence of the oxidation of iodide and ferrocyanide by compound I of horseradish peroxidase.
The kinetics of the oxidation of iodide and ferrocyanide by compound I of horseradish peroxidase have been studied at 25 degrees C as a function of ionic strength and pH. The ionic strength dependencies of the second-order rate constants are tested with an extended form of the Debye-Hückel equation for the activity coefficients of the reacting species. For the reaction of iodide with compound I it is shown that the pH variation of the rate constant at zero ionic strength is caused mainly by titrating a catalytically important acid group and not mainly by the varying charge of the protein. The ferrocyanide reaction rate with compound I does not correlate with enzyme net charge, at all pH values. The influence of electrostatic interactions on reaction rates is discussed.
D005295:Ferrocyanides; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007454:Iodides; D007700:Kinetics; D008433:Mathematics; D009994:Osmolar Concentration; D010544:Peroxidases / Q000378:metabolism*; D013816:Thermodynamics
D005295:Ferrocyanides; D007454:Iodides; D006735:Horseradish Peroxidase; D010544:Peroxidases