| Resumo: |
The emergence of tuberculosis resistant to multiple, first- and second-line antibiotics poses challenges to a global control strategy that relies on standard drug treatment regimens. The high drug-resistant strains of Mycobacterium tuberculosis (Mtb) have been implicated in outbreaks and have been found throughout the world; a comprehensive understanding, the magnitude of this threat requires an accurate assessment of the worldwide burden of resistance. In an attempt to design anti-TB drugs, the target chosen is a key enzyme of Mtb, O-Succinylbenzoate synthase (OSBS), which is an attractive target for its role in electron transport chain as OSBS is not available in humans. An attempt has been to built the 3-D structure of Mtb-OSBS using online Swiss model server. With sequence alignment and scan motif identification, the importance of evolutionarily significant residues that are of functional importance for ligand binding and that form active sites were well established. Molecular simulation calculations of Mtb-OSBS model indicated evolutionarily conserve residues (Lys110 and Lys212) are the best in molecular interaction with substrate 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC). The in silico mutational analysis of Mtb-OSBS model showed the evolutionarily conserved residues that are essential for catalytic activity. It has been found that active site amino acids of Mtb-OSBS are very important to maintain activity of the enzyme, which provides a novel approach to design new pharmacophore SHCHC substrate analogs against Mtb-OSBS. A series of SHCHC substrate analogs (1–100) compounds have been docked with the amino acid residues at the active site of the Mtb-OSBS enzyme, using AutoDock 4.0, a program employed to perform automated molecular docking. The free energies of binding (∆G) and inhibition constants (Ki) of the docked compounds were calculated by the Lamarckian Genetic Algorithm (LGA). Excellent to good correlations between the calculated and experimental Ki values were reported.
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