抄録
In the present report, the experiments were performed to prove that dihydrothiamine (DHB_1), assumed as the precursor of thiamine biosynthesis, was oxidatively converted to thiamine using the partially purified potato tyrosinase. The results indicated that the tyrosinase-catechol system catalyzed the oxidation of DHB_1 to thiamine to the extent of 20% only when both tyrosinase and catechol were added. Some of other phenolic compounds, such as guaiacol and L-tyrosine was less useful. This enzymatic oxidation showed rather sharp pH optimum between 6 to 7,and the results obtained at optimum pH showed that the amount of thiamine produced was proportional to catechol concentration and tyrosinase activity within a limited range. The possibility that DHB_1 may be a precursor of thiamine biosynthesis in nature was discussed.
