Steady-state kinetics of peroxidation of 2-chloro-10-(3-dimethylaminopropyl)-phenothiazine catalyzed by horseradish peroxidase

The steady-state kinetics of peroxidation of 2-chloro-10-(3-dimethylaminopropyl)-phenothiazine (Aminazine) catalyzed by horseradish peroxidase was studied. Aminazine was shown to be a substrate of peroxidase which is oxidized with a slow rate. The values of the catalytic constant (kcat) and Km were measured within the pH range from 4.5 to 7.0. In the presence of Aminazine, there was an increase in the rate of peroxidation of potassium ferrocyanide. Binding of an activator to the peroxidase active center caused an increase in the enzyme affinity for ferrocyanide, although had no effect on the kcat value within the pH range from 5 to 7.