Doctor of Philosophy (PhD)
Dr. Donald R. Ronning
Tuberculosis (TB) is one of the world’s oldest contagious diseases caused by Mycobacterium tuberculosis (M. tb). With the emergence and spread of drug-resistant M. tb strains, there is an urgent need to discover novel drugs and drug targets specifically against drug-resistant strains and dormant bacteria. This dissertation focuses on M. tbenzymes essential for the M. tb cell wall and ergothioneine biosynthesis. The M. tb cell wall acts as a protective barrier due to the presence of unique lipids and mycolic acids. Among these lipids, trehalose-dimycolate and mycolylarabinogalactan play a major role in constructing and maintaining the outer membrane (mycomembrane) of the cell wall. The Ag85 Complex (Ag85A, Ag85B, Ag85C) catalyzes the biosynthesis of these lipids. A previous student in our lab showed that tetrahydrolipstatin (THL), an FDA-approved lipase inhibitor, covalently binds to the Ag85C forming an acyl-enzyme intermediate. Based on this finding, a library of THL derivatives was synthesized and tested against Ag85C and Ag85A. As a result, a clear structure-activity relationship was observed for these derivatives. Thus, the structural and inhibitory information of this study can be utilized to develop selective novel inhibitors that target Ag85 enzymes. The second protein of interest is EgtD, an essential enzyme for ergothioneine biosynthesis in M. tb. Ergothioneine is a low molecular weight histidine betaine found in all domains of life. Ergothioneine is critical for maintaining bioenergetic homeostasis and protect M. tb against alkylating agents, oxidative stresses, and antitubercular drugs. Two strategies were implemented to discover inhibitors for EgtD; screened a library of histidine/histamine derivatives to identify peptide-like inhibitors targeting the L-Histidine binding site and screened drug libraries to identify drug-like inhibitors targeting the AdoMet binding site. This study presents inhibitory studies and X-ray co-crystal structures of a library of peptide-like inhibitors and the first discovery of indole-containing inhibitors and inhibitors against M. tb EgtD.
Sudasinghe, Thanuja D., "Structural and Inhibitory Studies of Enzymes Essential for Cell Wall and Ergothioniene Biosynthesis in Mycobacterium Tuberculosis" (2021). Theses & Dissertations. 567.