Lead identification and optimization of bacterial glutamate racemase inhibitors

Abstract

Mycobacterium tuberculosis glutamate racemase is an essential enzyme involved in peptidoglycan synthesis and conserved in most bacteria. Small molecule inhibitors were reported on other bacterial species whereas in M. tuberculosis it wasn't explored much. In this study we have screened in house compound library using fluorescence thermal shift assay and enzyme inhibition assay, form this (1-(3-(benzo[d]thiazol-2-yl)phenyl)-3-(p-tolyl)thiourea) was identified as lead compound with IC₅₀ 19.47 ± 0.81 μM. Further lead optimization by synthesis resulted in twenty-three compounds, of which Compound 25 has shown more efficacy compared to lead 1 showing non-competitive mode of inhibition with IC₅₀ 1.32 ± 0.43 μM. It also showed significant activity (represented in log reduction) in nutrient starved dormant M. tuberculosis model (2.1), M. tuberculosis biofilm assay (2.0) and in vivo M. marinum infected zebrafish model (3.5).

Keywords: Biofilm; Dormant tuberculosis; Fluorescence thermal shift assay; Glutamate racemase; Tuberculosis; Zebra fish.