抄録
Biosynthesis of thiamine from its pyrimidine and thiazole moieties by Sacch. cerevisiae harvested in the medium containing thiamine or its pyrimidine and thiazole moieties, was shown to be more retarded than that by cells harvested in the medium without thiamine or with either pyrimidine or thiazole moiety. When the cells harvested in the medium without thiamine, had been incubated with thiamine for 1 or 3 hours before the reaction of biosynthesis, no retardation for biosynthesis was demonstrated. Biosynthesis of thiamine by crude enzyme extracted from cells harvested in the thiamine-containing medium was also proved to be more retarded and less phosphorylated than that from cells in thiamine-free medium. Under the retarded biosynthesis of thiamine by yeast cells, it was shown that uptake of the pyrimidine moiety by cells from the medium was also repressed.
