W0161

Structural Studies on ThiO, a Glycine Oxidase Essential for Thiamin Biosynthesis in B. subtilis. Ethan C. Settembre, Pieter C. Dorrestein, Joo-Heon Park, Amy Augustine, Tadhg P. Begley and Steven E. Ealick, Cornell Univ., Dept. of Chemistry and Chemical Biology, Baker Lab, Ithaca, NY 14853.

The thiO gene of Bacillus subtilis encodes an FAD-dependent glycine oxidase. This enzyme is a homotetramer with a monomer molecular weight of 42 kDa. We have demonstrated that ThiO is required for the biosynthesis of the thiazole moiety of thiamin pyrophosphate and will describe the structure of the enzyme with N-acetylglycine bound at the active site. The closest structural relatives of ThiO are sarcosine oxidase and D-amino acid oxidase. The ThiO structure, as well as the observation that N-cyclopropylglycine is a good substrate, supports a hydride transfer mechanism for the enzyme. A mechanistic proposal for the role of ThiO in thiazole biosynthesis will also be described.