Development of novel pantothenate synthetase and lysine aminotransferase inhibitors against active and dormant tuberculosis

Abstract

Tuberculosis (TB) is the leading disease in the world today causing world-wide death among the infectious diseases and is responsible for the greatest morbidity and mortality. In this study we have focused on developing novel leads for the enzyme targets of infectious disease tuberculosis in both active and dormant forms. newlineWe employed computer-aided drug design tool, to identify new leads for Mycobacterium tuberculosis (Mtb) enzyme targets pantothenate synthetase (PS) and lysine aminotransferase (LAT). For Mtb PS we utilized the reaction intermediate and the inhibitor bound with active site of the protein. Energy-based pharmacophore hypotheses based on the crystal structures of Mtb PS bound to reaction intermediate and inhibitor were generated and validated using enrichment calculations. Further virtual high-throuput screening and docking were performed to identify new inhibitors for the targets. The leads identified were further modified using medicinal chemistry approach. From the first set of optimized leads, compounds Pa-9 and Pa-12 emerged as most potent Mtb PS leads with IC50s of 0.35and#61617;0.81 and#61549;M and 0.37and#61617;0.92 respectively; Mtb MIC of 0.38 and#61549;M and 0.85 and#61549;M respectively in the presence of efflux inhibitors. The stabilization of protein-ligand complexes was re-ascertained by differential scanning fluorimetry, wherein the melting temperature was monitored. All the top active hits showed a shift in Tm in the range of 2-4.3°C compared to the native protein which implied binding of inhibitors towards the protein. Compound Pa-12 was found to be effective against dormant Mtb. newlineFor the second enzyme target Mtb LAT, we employed similar approach as mentioned above. As there were no inhibitors available for this enzyme target, we employed two crystal structures from protein data bank that were bound with substrates like lysine and and#61537;-ketoglutarte to design leads. Compounds La-1 and La-17 exhibited good inhibition of Mtb LAT at IC50s of 4.09and#61617;0.09 and#61549;M and 4.34and#61617;0.01 and#61549;M respectively; whereas, compounds La-28 and La-30 showed IC50s.