It has been shown that the experimental results obtained by Morgulis in a study of the decomposition of hydrogen peroxide by liver catalase at 20°C. and in the presence of an excess of a relatively high concentration of peroxide are quantitatively accounted for by the following mechanisms.
1. The rate of formation of oxygen is independent of the peroxide concentration provided this is greater than about 0.10 M.
2. The rate of decomposition of the peroxide is proportional at any time to the concentration of catalase present.
3. The catalase undergoes spontaneous monomolecular decomposition during the reaction. This inactivation is independent of the concentration of catalase and inversely proportional to the original concentration of peroxide up to 0.4 M. In very high concentrations of peroxide the inactivation rate increases.
4. The following equation can be derived from the above assumptions and has been found to fit the experiments accurately.
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in which x is the amount of oxygen liberated at the time t, A is the total amount of oxygen liberated (not the total amount available), and K is the inactivation constant of the enzyme.