Abstract
Enzymatic properties of partially purified O-acylthiamine oxidase from rat liver were investigated. Optimal pH for this enzyme was about 8.5-9.0. The activity was inhibited by metal chelating agents, such as KCN, diethyldithiocarbamate or o-phenanthroline and sulfhydryl reagents, such as PCMB or NEM. The enzyme reaction proceeds scarcely in anaerobic condition, but do by an addition of DCPI, and the enzyme was considered to be a kind of oxidase which requires molecular oxygen as hydrogen acceptor. The enzyme was supposed to be one of metalloflavoproteins since it was inhibited by FAD antagonist. On the base of above properties of this enzyme, the mechanism was proposed that thiamine thiazolone was formed by enzymatic dehydrogenation from pseudobase type O-acylthiamine. This mechanism was supported by the fact that the maximal activity was exhibited in the region of pH 8.5-9.0,where concentration of the pseudobase type is considered to be maximum.
