Peroxidase experiment with oxygen

In a reinvestigation of this cyanide effect, the writer found a stimulation of both enzymic and nonenzymic reactions by cyanide at low DHF concentrations (Nicholls, 1959, 1961). In manometric experiments, Theorell had to use 5 mM DHF or more to obtain measurable oxygen uptakes. Under these conditions, both peroxidase and cyanide stimulate autoxidation, and the interaction is difficult to measure. Some inhibition can usually be observed, however, if the rate with cyanide alone be subtracted from the combined rate (that is, the two effects are not additive). In spectrophotometric experiments, much lower DHF concentrations can be used (10 to 10 M) and at 10 MDHF, the addition of cyanide is invariably stimulatory to both oxidations. The reaction rate in air at pH 4.6 and 20°C. is reported as shown in Eq. (11) (Nicholls, 1961). 

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