Investigating an unusual flavin-dependent mechanism of thymidylate biosynthesis

摘要

Biosynthesis of DNA depends on thymidylate synthase that catalyzes the reductive methylation of uridylate to form the essential base thymidylate. Two classes of thymidylate synthases are known. Humans and all other eukaryotes rely on thyA-encoded TSase, whereas, many microorganisms including several severe pathogens rely on the thyX-encoded flavin-dependent thymidylate synthase (FDTS).This dissertation describes research conducted to delineate the molecular mechanism of FDTS enzymes, and identify distinguishing features from that of classical TSases. Most notably, the findings presented in Chapter II indicate the mechanism of FDTS catalysis is unique to pyrimidine methylation in that it does not involve a covalent enzyme-substrate complex during the reaction.This work further investigates this unusual mechanism, by constructing a more thorough picture of the reaction through characterization of intermediates as shown in Chapter III. Additional studies regarding the structure, substrate binding patterns, FAD cofactor chemistry, and oxidase activity are presented in Chapters IV and V.Overall the work presented here impacts our general knowledge about pyrimidine methylation strategies, and could potentially set the groundwork for mechanism-based rational inhibition of FDTS enzymes leading to possible antibiotic compounds.