ORIGIN OF THE NITROGEN ATOM OF PYRIDOXINE IN SACCHAROMYCES-CEREVISIAE

The origin of the nitrogen atom of pyridoxine was studied in Saccharomyces cerevisiae. The N-15 atom of (NH4Cl)-N-15 added to the growth medium as the nitrogen source was incorporated efficiently into the nitrogen atom of pyridoxine. The competitive effects of N-14-amino acids on the incorporation of (NH4Cl)-N-15 were examined. Incorporation of N-15 into pyridoxine was inhibited by glutamine. The label of L-[amide-N-15]glutamine was incorporated effectively into pyridoxine in S. cerevisiae. On the other hand, the label from L-[amide-N-15]glutamine was not incorporated into pyridoxine in Escherichia coli. These findings suggest that the biosynthetic pathway of pyridoxine in S. cerevisiae differs from that in E. coli.