Abstract
The cell suspensions of baker's yeast and a thiamine requiring mutant of E. coli (OMP-less, 70-17) are able to synthesize a thiamine analogue, 2-nor-thiamine from 2-nor-OMP and thiazole. This is determined fluorometrically and bioautographically by paper partition chromatography after treatment of the extract with Takadiastase. The formation of 2-nor-thiamine by yeast was limited and showed substrate inhibition differing from thiamine synthesis from OMP. The OMP-less mutant of E. coli had response for growth in 1×10^<-9>-10×10^<-9>M 2-nor-OMP or 2-nor-thiamine, but the activity was 70% of OMP or thiamine. The growing cells of the mutant in the presence of 2-nor-OMP produced 2-nor-thiamine, probably its esterified form, not thiamine. In addition, they pyroduced a larger amount of 2-nor-thiamine than they can produce thiamine in the presence of same molar OMP. This indicates that the mutants grow by utilizing 2-nor-thiamine formed and can not convert it to thiamine. The concentrates obtained from the extracts of the growing cells supplemented with 2-nor-OMP or OMP were subjected to estimation of the cocarboxylase activity manometrically using partially purified apocarboxylase from baker's yeast. The cell extracts supplemented with 2-nor-OMP showed much lower activity than that of the cell extracts supplemented with OMP, though the former contained much more esterified compound as determined by the thiochrome method than the latter.
