Abstract
The enzyme preparations obtained from acetone powders of 5 kinds of green leaves contained the enzyme system responsible for the synthesis of thiamine from pyrimidine (2-methyl-4-amino-5-hydroxymethylpyrimidine) and thiazole (4-methyl-5-β-hydroxyethylthiazole) moieties. The condensation reaction of the moieties was dependent upon the presence of ATP and Mg2+. The enzyme preparations showed the optimal activity at around pH 7.5 and lost its activity abruptly beyond 48°.
The rate of thiamine synthesis increased with the increase of ATP concentration and reached an optimum. Beyond the optimum, the rate decreased as ATP concentration increased. The additional Mg2+ not only accelerated the rate but also partially removed the inhibition by ATP. In addition to Mg2+, Mn2+ and Co2+ also activated the thiamine synthesis.
