Nonstationary inhibition of enzyme Action. The cyanide inhibition of catalase

Various modes of inhibition, on the basis of the peroxidatic mechanism of enzyme action, have been studied The system was not assumed to be in a steady state. The course of the reaction depended on whether the inhibition process was rapid or slow compared to the rate of catalysis. In the case of a rapid equilibrium with the inhibitor, the concentration of the active intermediate always increased in time up to a plateau. Quantitative relations between the initial concentration of the substrate and the final concentration of the active intermediate were derived for the various types of inhibition. In the case of slow equilibrium, and for uncompetitive and noncompetitive inhibition, the concentration of the active intermediate passed through a maximum and then declined to a finite value. The data of Chance on the effect of cyanide on the spectrum of the catalase-H₂O₂ system have been examined. It has been shown that the data were consistent with the assumption of non-competitive inhibition of the system by cyanide. The enzyme substrate intermediate formed a looser complex with cyanide than the free enzyme itself.