Abstract
It has been known that formate is incorporated into the pyrimidine moiety of thiamin with only small dilution of specific activity by some microorganisms. However, some disagreements have arisen regarding the specific carbons of the pyrimidine that are derived from formate. David et al. reported that formate is incorporated only into C-4 of the pyrimidine in Saccharomyces cerevisiae, whereas Johnson et al. reported the methyl group attached to C-2 is derived from formate. The present investigations were carried out to determine which pyrimidine carbon atoms are labeled when S. cerevisiae is grown in the presence of [^<14>C] formate. The results of degradative reactions different from the methods by David et al. and Johnson et al. show that formate is incorporated into C-4 of the pyrimidine in S. cerevisiae.
