Thiamin is synthesized by most prokaryotes and by eukaryotes such as yeast and plants. In
all cases, the thiazole and pyrimidine moieties are synthesized in separate branches of the
pathway and coupled to form thiamin phosphate. A final phosphorylation gives thiamin
pyrophosphate, the active form of the cofactor. Over the past decade or so, biochemical and
structural studies have elucidated most of the details of the thiamin biosynthetic pathway in
bacteria. Formation of the thiazole requires six gene products, and formation of the …