Abstract
Studies on the biosynthesis of 4-methyl-5-β-hydroxyethylthiazole-monophosphate from 4-methyl-5-β-hydroxyethylthiazole were carried out by means of bioautography with thiazole-less and pyrimidine-less mutants of Escherichia coli. It was observed that thiazole phosphate was produced in the yeast cells when either Saccharomyces cerevisiae was cultivated in the Reader's medium containing thiazole or the yeast suspension in a buffer solution containing glucose and thiazole was incubated at 37℃. It was found that the thiazole-kinase in the yeast extract was considerably stable in the range of pH 4.2 to 8.0,and its optimal pH was between 5.8 and 7.8. Thiazole-kinase was inactivated at 65℃ for 10 minutes and not perfectly inactivated at 55℃. It was assumed that the rate limiting process in the biosynthesis of thiamine by the yeast extract might be the activation of 2-methyl-4-amino-5-hydroxymethylpyrimidine.
