Abstract
The biosynthetic pathway of the pyrimidine moiety of thiamin in Saccharomyces cerevisiae, a eucaryote, is different from that of procaryotes. In procaryotes, the pyrimidine moiety is synthesized from 5-aminoimidazole ribonucleotide, an intermediate in purine biosynthesis. This has been demonstrated by investigating the nutritional requirement of adenine- and thiamin-requiring mutants of Salmonella typhimurium and by tracer experiments with radioactive compounds in Escherichia coli and S. typhimurium. We investigated pyrimidine biosynthesis in S. cerevisiae by GC-MS analysis using a stable isotope labeled tracer. Origin of the C-4 of pyrimidine was determined by a radioactive tracer method. These experiments showed that in S. cerevisiae, the pyrimidine moiety is synthesized from histidine and pyridoxine.
