Biosynthesis of thiazole from thiamine in Escherichia coli]

The incorporation into the thiazole moiety of thiamine of several labeled compounds has been studied on short time incubations of washed-cells suspensions. No incorporation of radioactivity from G-14C] methionine was found in a mutant auxotrophic for methionine. No radioactivity was incorporated from U-14C] aspartate or from U-14C] serine. The incorporation of 35S from sulphate was lowered by cysteine or glutathione but was unaffected by methionine or homocystine. Although the synthesis of thiazole is dependent on methionine, neither the sulphur atom nor the carbon chain of thiazole originate from methonine in E. coli. No carbon originates from cysteine which is the likely direct donor of sulphur.