Abstract
Studies on the biosythesis of thiamine from 2-methyl-4-amino-5-hydroxymethyl-pyrimidine and 4-methyl-5-β-hydroxyethylthiazole under the existence of ATP and Mg^<..> were carried out by using a precipitated enzyme obtained by 0.65 saturation of the yeast extract with ammonium sulfate. It was recognized that the optimal pH for the crude enzyme was 7.4 and it was stable at the pH value. This crude enzyme was completely inactivated at 45℃ for 10 minutes, and about 60% of the activity was lost at 37℃. The maximum synthesis of thiamine was observed when the yeast extract was incubated for 2 hours at 37℃. The lag time for the synthesis of thiamine was observed at the initial state of the incubation (from 5 to 10 minutes). Therefore, it was assumed that the activation of the substrates might take place at the initial state.
