The Primary and Secondary Compounds of Catalase and Methyl or Ethyl Hydrogen Peroxide

The catalase-ethyl hydrogen peroxide compound studied by Stern (1) formed slowly, even in the presence of a very large concentration of ethyl hydrogen peroxide. In the previous paper (2), Stern’s compound has been shown to be preceded by a green primary compound. These kinetic studies show that the primary compound forms rapidly, has a high affinity* for its substrate, and quantitatively fulfils the requirements for a Michaelis intermediate. The primary compound of catalase and methyl hydrogen peroxide has similar properties. Keilin and Hartree have demonstrated the oxidation of ethanol to acetaldehyde by catalase and ethyl hydrogen peroxide (3). Whereas they believed that this peroxidatic oxidation was caused by the production of hydrogen peroxide from ethyl hydrogen peroxide, the reaction is shown here to be a peroxidatic reaction of the primary catalase ethyl hydrogen peroxide compound with ethanol. The oxidation of acceptors2 such as the lower alcohols is a property common to the primary catalase alkyl hydrogen peroxides and catalase hydrogen peroxide (4). The reactivity of these three compounds towards alcohols is about the same. The variation of the velocity of the reaction of catalase with alkyl hydrogen peroxide and with alcohols of different sizes indicates that the accessibility of the iron atom in catalase hematin is limited to small substrate and acceptor molecules. The relative reactivity of the primary and secondary enzyme-substrate compounds towards alcohols has been evaluated and the inhibition of the oxidation of alcohols by the formation of the secondary catalase alkyl hydrogen peroxide compounds is demonstrated.