Discovery of a Pyrimidinedione Derivative with Potent Inhibitory Activity against Mycobacterium tuberculosis Ketol–Acid Reductoisomerase

Abstract

New drugs aimed at novel targets are urgently needed to combat the increasing rate of drug‐resistant tuberculosis (TB). Herein, the National Cancer Institute Developmental Therapeutic Program (NCI‐DTP) chemical library was screened against a promising new target, ketol–acid reductoisomerase (KARI), the second enzyme in the branched‐chain amino acid (BCAA) biosynthesis pathway. From this library, 6‐hydroxy‐2‐methylthiazolo[4,5‐d]pyrimidine‐5,7(4H,6H)‐dione (NSC116565) was identified as a potent time‐dependent inhibitor of Mycobacterium tuberculosis (Mt) KARI with a Ki of 95.4 nm. Isothermal titration calorimetry studies showed that this inhibitor bound to MtKARI in the presence and absence of the cofactor, nicotinamide adenine dinucleotide phosphate (NADPH), which was confirmed by crystal structures of the compound in complex with closely related Staphylococcus aureus KARI. It is also shown that NSC116565 inhibits the growth of H37Ra and H37Rv strains of Mt with MIC50 values of 2.93 and 6.06 μm, respectively. These results further validate KARI as a TB drug target and show that NSC116565 is a promising lead for anti‐TB drug development.

Characterization of a class II ketol-acid reductoisomerase from Mycobacterium tuberculosis

“…By this assay, MtKARI-II was found to have catalytic parameters that are in good agreement with those reported for EcoKARI with k cat = 2.23 ± 0.1 s −1 , K M = 250 ± 30 μM, 18 MtKARI with k cat = 1.4 ± 0.02 s −1 , K M = 110 ± 4 μM (ref. 1 ) (Table S1 † ) and MtH37Rv (Mtb-Rv) and Mt H37Ra (Mtb-Ra) strains with a K M = 110 ± 4 μM. 18 MtKARI-II also displayed similar catalytic parameters to that found for KARIs from other microorganisms, suggesting a conserved reaction mechanism (Table S1 † ).…”

“… 6 Animals, including humans, do not have this pathway and rely on obtaining BCAAs from their diet. 1 In this respect, the BCAA pathway makes it an attractive target for antimicrobial lead compound discovery. 7 A typical pathway of BCAAs, such as valine, starts with an acetohydroxyacid synthase (AHAS) which acts on two molecules of pyruvate 1 via a decarboxylation and subsequent condensation to generate acetolactate 2 ( Fig.…”

“… 14 MtKARI is a typical class I KARI with a sequence length of 337 amino acid residues which only utilize NADPH as the reducing agent. 1 …”

Unveiling of Pyrimidindinones as Potential Anti-Norovirus Agents—A Pharmacoinformatic-Based Approach

“…Besides, 6-hydroxy-2-methylthiazolo [4,5-d]pyrimidine-5,7(4H,6H)-dione (NSC116565) has been identified as potential lead compound for anti-tuberculosis drug. nsC116565 hinders the growth of H37Ra and H37Rv strains of mycobacterium tuberculosis with MIC50 values of 2.93 µM and 6.06 µM, respectively [40]. Hence, we deduce that developing the potent and noncytotoxic lead compounds ZINC1617939 and ZINC1642549 as a drug candidate for treating HNV infection will be effective.…”

Cell-Penetrating Peptides-Based Liposomal Delivery System Enhanced Immunogenicity of Peptide-Based Vaccine against Group A Streptococcus

“…The cytotoxicity of L1 , L3 , and L14 was assessed using HEK-293 (human embryonic kidney) cell line, following previously reported methods [ 38 , 39 ]. HEK-293 Cells were seeded into 96-well microtiter assay plates at a density of 8 × 10 3 cells in 190 μL per well of DMEM or RPMI complete media, respectively.…”