On the oxidation of dihydrothiamine by the peroxidatic reaction of liver catalase.

As reported in the previous paper, dihydrothiamine (DHT), does not seem to be oxidized in biological systems by pyridine nucleotide enzymes or flavin enzymes in view of a high redox-potential of DHT (1). Its possible mecha nism, therefore, is assumed to be oxidation of DHT by a coupled oxidation at a terminal step of the respiratory system by a specific oxidase. Uehara's observation of the oxidation of DHT by radish peroxidase in the presence of H2O2 (2), seems to be an information quite worthy of note in this connection On the other hand, it is well known, that the peroxidatic effi ciencies of various heme-proteins are variable depending on the kinds of sub strates employed (3). Therefore, the experiments of DHT oxidation coupled to the glucose oxidase-catalase system were undertaken.