Biosynthesis of thiamin. The precursor of the five-carbon unit of the thiazole moiety.

The precursor of the thiazole moiety of thiamin in Candida utilis was identified. Radioactive C-2, 3, 4, 5 and 6 of glucose was incorporated into C-4', 4, 5, 5' and 5" of the thiazole. This experiment shows that the precursor of the five carbon unit of thiazole is a 5-carbon compound such as ribose or ribulose derived from glucose.