Different biosynthetic pathways of the pyrimidine moiety of thiamin in procaryotes and eucaryotes

¹⁴C]Formate is incorporated into the C-2 of the pyrimidine moiety of thiamin by Escherichia coli and Salmonella typhimurium. In Saccharomyces cerevisiae, it is incorporated into C-4. Radioactive carbons of 1-¹⁴C]glycine and 2-¹⁴C]glycine are incorporated by S. typhimurium into the C-4 and C-6 of the pyrimidine, respectively, but not by S. cerevisiae. These facts suggest that procaryotes and eucaryotes have different biosynthetic pathways for pyrimidine. In this study, the procaryotes tested incorporated ¹⁴C]formate into the C-2 and the eucaryotes incorporated it into the C-4 of the pyrimidine.