Mechanism of N-Demethylation of Aminopyrine by Catalase-Organic Hydroperoxide Systems

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Cumene hydroperoxide (CHP)-and ethyl hydroperoxide (EHP)-supported oxidations of aminopyrine catalyzed by catalase were investigated by electron spin resonance (ESR) studies. The oxidations were also monitored through the measurement of formaldehyde. The EHP-supported oxidation of aminopyrine went to completion within 5 min and was inhibited by sodium azide. When EHP was added to catalase prior to the addition of aminopyrine, the ESR signal intensity of the aminopyrine free radical and the concentration of formaldehyde did not increase to appreciable values. This retardation of the oxidation of aminopyrine was considerably relieved by previously adding sodium azide to catalase. The rate of EHP-supported oxidation of methanol was comparable to that of aminopyrine. CHP previously added to catalase inhibited the EHP-supported oxidation of aminopyrine, whereas it did not inhibit that of methanol. The present results suggest that the active site of catalase for the EHP-supported oxidation of aminopyrine is different from that for the oxidation of methanol.