BIOSYNTHESIS OF THIAMIN .4. C-2 OF GLYCINE AS PRECURSOR OF C-2 OF THIAZOLE MOIETY IN YEAST

[2-14C]Glycine was fed to growing cells of Saccharomyces cerevisiae in the presence of a large excess of unlabelled L-methionine. The thiazole moiety of thiamin was obtained from the cells and purified using a revised procedure. Incorporation of activity into the thiazole was not diminished significantly by methionine competition. This suggests that the C-2 glycine is a closer precursor of the C-2 of the thiazole ring than is the methyl carbon atom of methionine in the system studied. It has been shown that there was an insignificant incorporation of label from [1-14C]glycine, [3-14C]serine and [14C]formate into the purified thiazole moiety. Possible pathways for thiazole biosynthesis are discussed in the light of the available data. © 1969.