Desidroquinato desidratase (EC 4.2.1.10) e chiquimato desidrogenase (EC 1.1.1.25) de Mycobacterium tuberculosis como alvos para o desenvolvimento de novos fármacos contra a Tuberculose

Abstract

Tuberculosis (TB) is the leading cause of bacterial infectious disease mortality. The etiological agent, Mycobacterium tuberculosis (Mtb) is responsible for 1.5 million deaths and 9 million people infected in 2013. The World Health Organization (WHO) estimates that one-third of the world´s population is infected with latent form of Mtb. Thus, there is a continuous need to find promising molecular targets for the development of anti-TB agents. The shikimate pathway produces an important precursor of aromatic compounds in bacteria, fungi, plants and apicomplexan parasites, chorismate. The pathway comprises seven enzymes, which convert erythrose-4-phosphate and phosphoenolpyruvate into chorismate, the precursor for the synthesis of aromatic amino acids, folic acid, ubiquinone, and many other aromatic compounds. This pathway is essential for growth of Mtb. The aroD gene, that codes for 3-dehydroquinate dehydratase (DHQase), catalyzes the reversible reaction of 3-dehydroquinate into 3-dehydroshikimate and the aroE gene, that codes for the NADP(H) dependent shikimate-5-dehydrogenase (SD), catalyzes the reduction of 3-dehydroshikimate into shikimate. The aim of the present study was to identify new dug-like molecules as inhibitors for MtbDHQase and MtbSD using structure-based modeling and virtual screening. The availability of the crystal structure bound with an inhibitor of MtbDHQase was explored using pharmacophore models based on interaction energy and docking to yield diverse leads. For MtbSD, due the absence of crystal structure and reported inhibitors, the tridimensional structure was achieved by molecular modelling. Structure-based pharmacophore and virtual screening of the in house database containing 3000 unique molecules retrieved twelve hit compounds with good docking score and interaction pattern for MtbDHQase. For MtbSD, the commercially available database Asinex, with 500,000 molecules, were used and seventeen compounds were selected based in its docking score, interaction pattern with amino acids in the active site, number of hydrogen bonds and GOLD score. MtbDHQase inhibitors were tested and, after inhibition assay, series of chemical modifications were made in the lead compound. The top two derivate presented IC50 values of 17.1 and 31.5 μM as well as MIC values of 25 and 6.25 μg/mL and cytotoxicity below 15% at 100 μM respectively. The MtbSD compounds selected as possible inhibitors will be tested for inhibition, MIC value and cytotoxicity.