Structure Guided Lead Generation toward Nonchiral <i>M. tuberculosis</i> Thymidylate Kinase Inhibitors

TLDR

Thymidylate kinase is essential for bacterial DNA synthesis and has been targeted for new antibacterial agents against Mycobacterium tuberculosis. The study designs a novel series of non‑nucleoside inhibitors of MtTMPK to address the need for more effective anti‑TB drugs. The authors examined the discrepancy between enzyme inhibition and whole‑cell activity by testing efflux pump inhibitors and creating efflux pump knockout mutants. The inhibitors reveal unique active‑site interactions that inform structure–activity relationships, and their minimum inhibitory concentrations rise markedly in an efflux‑pump‑knockout mutant, partially explaining the activity gap.

Abstract

In recent years, thymidylate kinase (TMPK), an enzyme indispensable for bacterial DNA biosynthesis, has been pursued for the development of new antibacterial agents including against Mycobacterium tuberculosis, the causative agent for the widespread infectious disease tuberculosis (TB). In response to a growing need for more effective anti-TB drugs, we have built upon our previous efforts toward the exploration of novel and potent Mycobacterium tuberculosis TMPK (MtTMPK) inhibitors, and reported here the design of a novel series of non-nucleoside inhibitors of MtTMPK. The inhibitors display hitherto unexplored interactions in the active site of MtTMPK, offering new insights into structure–activity relationships. To investigate the discrepancy between enzyme inhibitory activity and the whole-cell activity, experiments with efflux pump inhibitors and efflux pump knockout mutants were performed. The minimum inhibitory concentrations of particular inhibitors increased significantly when determined for the efflux pump mmr knockout mutant, which partly explains the observed dissonance.