A study of the inhibition of catalase by 3-amino-1:2:4-triazole

Abstract

3-Amino-l,2,4-triazole caused a complete, irreversible and relatively rapid inhibition of crystalline purified preparations of liver and erythrocyte catalase in the presence of low and constant concentrations of H2O2. Without H2O2 the inhibition of catalase by 3-amino-l,2,4-triazole was slight and proceeded much more slowly. Other substances that could replace H2O2 required the presence of O2, and it is con-sidered that they acted by producing peroxide by auto-oxidation. Ferricyanide, but not ferrocyanide, prevented this inhibition. The spectrum of inhibited catalase differed from that of catalase. The visible part of the spectrum was shifted towards the longer wave lengths, and the Soret band was slightly lowered. Inhibited catalase was obtained in a crystalline form that did not differ from that of uninhibited catalase. The ability of catalase inhibited by 3-amino-l,2,4-triazole to oxidize ribose 5-phosphate with potassium ferricyanide as hydrogen acceptor was unchanged. In the presence of O2, but in the absence of added H2O2, 3-amino-l,2,4-triazole caused the inhibition of catalase in liver and kidney suspensions, but had no effect in blood hemolysates. The catalatic activity of blood hemolysates could be inhibited by 3-amino-l,2,4-triazole only in the presence of added H2O2.