Abstract
There are different biosynthetic pathways of the pyrimidine moiety of thiamin in Saccharomyces cerevisiae and Escherichia coli under aerobic and anaerobic conditions. The precursors of the pyrimi dine under anaerobic conditions have not been established. To elucidate the precursors of the pyrim dine under anaerobic conditions, the incorporation of the labels of following compounds, [2,2,3,3-D] succinate, [1-^<13>C]glycine and [2-^<13>C]glycine, into the pyrimidine was studied. The labels of [2,2,3,3-D]succinate were not incorporated into the pyrimidine under anaerobic con ditions in E. coli and S. cerevisiae. These results suggested that succinate had no relation to the bio synthesis of the pyrimidine. The labels of[1-^<13>C]glycine and [2-^<13>C]glycine were incorporated into C-4 and C-6 of the pyrimi dine respectively under anaerobic conditions as well as aerobic conditions in E. coli. We already reported that N atom of glycine, the precursor of N-1 of the pyrimidine under aerobic conditions, was incorporated into it under anaerobic conditions. These results showed that glycine was the precursor of the pyrimidine under anaerobic conditions as well as aerobic conditions.
