Thiamine Biosynthesis in Escherichia coli: Identification of the Intermediate and By‐Product Derived from Tyrosine

In anaerobic organisms such as E. coli the tyrosine lyase ThiH is essential for the biosynthesis of the thiazole moiety of the vitamin thiamine. ThiH is a member of the “radical AdoMet” family. The products formed by cleavage of tyrosine in vitro have been identified and suggest a radical-mediated cleavage resulting in p-cresol and dehydroglycine which is hydrolyzed to glyoxylate.