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Previous issue date: 2013-08-15 === Since its discovery, Isoniazid remains the main drug used to treat tuberculosis, which has the 2-trans-enoyl-ACP(CoA) reductase or InhA enzyme of Mycobacterium tuberculosis as pharmacological target. However, the increase in cases of tuberculosis resistant to Isoniazid motivated the pharmaceutical industry and research groups to investigate possible inhibitors to InhA, whether seeking for new compounds that display the inhibitory function, or as proposed in this work, modifying existing compounds. Thus, we believe that the IQG607 inorganic compound, also known as pentacyano(Isoniazid)ferrate (II) - developed in an attempt to find new, more potent and selective inhibitors of the InhA enzyme - is a promising candidate for the development of new anti-tuberculosis drugs. This work began with a literature review in order to understand the role of InhA enzyme in the process of fatty acid synthesis and what they represent in the process of formation of the cell envelope of mycobacteria. In addition, a survey was conducted regarding the published studies on the IQG607, which reported efforts engaged in researching and obtaining the compound. Based on these studies, it was proposed the design of new compounds by introducing structural modifications in the IQG607 molecule, with the aid of specific software. Intermolecular interactions of these compounds with the target protein were simulated and evaluated with the use of AutoDock and LigPlot. Twenty-seven models were designed, and for all of them, simulations were performed in silico. Three of these compounds were selected, and from those one was successfully synthesized. After synthesis, enzymatic assays were carried out to assess whether the new compound haddemonstrated inhibitory function as found in the original IQG607. Unfortunately, although the in silico simulations have led us to believe that the models designed could generate good compounds, early in the in vitro experiments we found that there was no variation in the enzyme s activity, indicating that the compound showed no inhibitor effect. In our attempt to lengthen the IQG607 compound - thus allowing a greater number of torsion angles for the molecule, and thereby promote a better fit of the ligand binding cavity in the substrate - we discovered that two important pieces of INH were separated, which caused the loss of activity of the compound. It appears that the changes which were introduced in the IQG607 compound have hindered the acyl radical formation and therefore the adduct ligand-NADH could not be formed. === Desde a sua descoberta, a Isoniazida continua sendo o principal f?rmaco empregado no tratamento da tuberculose, tendo como alvo farmacol?gico a enzima 2-trans-enoil- ACP(CoA) redutase ou InhA de Mycobacterium tuberculosis. Por?m, o aumento dos casos de tuberculose resistente ? Isoniazida motivaram a ind?stria farmac?utica e pesquisadores a investigar poss?veis inibidores da InhA, seja buscando novos compostos que apresentem a caracter?stica inibit?ria, ou como na proposta deste trabalho, modificando compostos j? existentes. Desta forma, acreditamos que o composto inorg?nico IQG607, tamb?m conhecido como pentaciano(isoniazida)ferrato (II), desenvolvido na tentativa de encontrar novos inibidores mais potentes e seletivos para a enzima InhA, ? um candidato promissor ao desenvolvimento de novas drogas anti-tuberculose. Este trabalho iniciou com uma pesquisa na literatura cient?fica buscando compreender o papel da enzima InhA no processo de s?ntese de ?cidos graxos e o que estes representam no processo de forma??o do envelope celular das micobact?rias. Al?m disso, foi realizado um levantamento a respeito dos estudos j? publicados sobre o IQG607, que relatam os esfor?os empenhados na pesquisa e obten??o do composto. Com base nestes estudos, foi proposto o desenho de novos compostos introduzindo modifica??es estruturais na mol?cula do IQG607 original, com o auxilio de software espec?fico. As intera??es intermoleculares desses compostos com a prote?na alvo foram simuladas e avaliadas, com o uso dos programas AutoDock e LigPlot. Vinte e sete modelos foram desenhados, e para todos eles foram realizadas as simula??es in silico. Tr?s desses compostos foram selecionados e, deles, um foi sintetizado com sucesso. Ap?s a s?ntese, ensaios enzim?ticos avaliaram se o novo composto mantinha a fun??o inibit?ria comprovadamente encontrada no IQG607 original, caracterizando a etapa in vitro deste trabalho. Infelizmente, embora as simula??es in silico tenham nos levado a crer que os modelos desenhados poderiam gerar bons compostos, j? no in?cio da etapa in vitro se descobriu que n?o havia varia??o na atividade da enzima, o que indica que o composto n?o apresentou o efeito inibit?rio esperado. Em nossa tentativa de alongar o composto IQG607, permitindo assim um n?mero maior de ?ngulos de tor??o para a mol?cula, e com isso, promover um melhor encaixe do ligante na cavidade de liga??o do substrato, descobrimos que dois grupamentos importantes da INH foram separados, o que provocou a perda de atividade do f?rmaco. Sup?e-se que as modifica??es introduzidas no composto IQG607 impediram a forma??o do radical acil e, portanto, o aduto com o NADH n?o p?de ser formado.
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