A 96-well microtiter plate assay for high-throughput screening of Mycobacterium tuberculosis dTDP-d-glucose 4,6-dehydratase inhibitors.

Mycobacterium tuberculosis dTDP-d-glucose 4,6-dehydratase (RmlB) is the second enzyme for the biosynthesis of dTDP-l-rhamnose, which is a sugar donor to the synthesis of the cell wall linker, d-N-acetylglucosamine-l-rhamnose. RmlB is essential to mycobacterial growth and is not found in humans; therefore, it is a potential target for developing new anti-tuberculosis drugs. So far, there has been no suitable method for high-throughput screening of RmlB inhibitors. Here, the recombinant M. tuberculosis RmlB was purified and an absorbance-based microtiter plate assay was developed for RmlB activity. It could be used for high-throughput screening of RmlB inhibitors. The kinetic properties of M. tuberculosis RmlB, including optimal pH, optimal temperature, the effect of metal ions, and the kinetic parameters, were determined with this assay. The inhibitory effects of dTTP and dTDP on M. tuberculosis RmlB were also studied with the assay.

Virtual screening for the identification of novel inhibitors of Mycobacterium tuberculosis cell wall synthesis: inhibitors targeting RmlB and RmlC.

BACKGROUND: Tuberculosis remains one of the deadliest infectious diseases in humans. It has caused more than 100 million deaths since its discovery in 1882. Currently, more than 5 million people are infected with TB bacterium each year. The cell wall of Mycobacterium tuberculosis plays an important role in maintaining the ability of mycobacteria to survive in a hostile environment. Therefore, we report a virtual screening (VS) study aiming to identify novel inhibitors that simultaneously target RmlB and RmlC, which are two essential enzymes for the synthesis of the cell wall of M. tuberculosis. METHODS: A hybrid VS method that combines drug-likeness prediction, pharmacophore modeling and molecular docking studies was used to indentify inhibitors targeting RmlB and RmlC. RESULTS: The pharmacophore models HypoB and HypoC of RmlB inhibitors and RmlC inhibitors, respectively, were developed based on ligands complexing with their corresponding receptors. In total, 20 compounds with good absorption, distribution, metabolism, excretion, and toxicity properties were carefully selected using the hybird VS method. DISCUSSION: We have established a hybrid VS method to discover novel inhibitors with new scaffolds. The molecular interactions of the selected potential inhibitors with the active-site residues are discussed in detail. These compounds will be further evaluated using biological activity assays and deserve consideration for further structure-activity relationship studies.