Caracterização bioquímica, dinâmica molecular e propriedades imunomoduladoras da prolil oligopeptidase de Mycobacterium tuberculosis

Abstract

A linha de pesquisa do nosso grupo visa à identificação e caracterização de alvos potenciais para a quimioterapia de doenças como a de Chagas, Dengue, Leishmaniose e Tuberculose tendo as proteases como principal enfoque, uma vez que estão envolvidas em processos biológicos fundamentais para a viabilidade e virulência de patógenos. Neste contexto, esta tese aborda alguns aspectos bioquímicos, estruturais e funcionais da prolil oligopeptidase de Mycobacterium tuberculosis, microrganismo responsável por desencadear uma resposta inflamatória característica da tuberculose. A prolil oligopeptidase de Mycobacterium tuberculosis (rPOPMt) revelou possuir atividade catalítica sobre o substrato N-Suc-Gly-Pro-Leu-Gly-Pro-AMC, com uma atividade ótima a pH 7,5 e temperatura ótima a 28 °C. Aditivos como NaCl, DTT e íons não influenciaram a atividade enzimática da proteína. Os parâmetros cinéticos calculados para a enzima foram Km e kcat/Km de 108 μM e 21.838 mM-1 .s-1, respectivamente, com N-Suc-Gly-Pro-Leu-Gly-Pro-AMC como substrato. Neste contexto, esta tese aborda alguns aspectos bioquímicos, estruturais e funcionais da prolil oligopeptidase de Mycobacterium tuberculosis, microrganismo responsável por desencadear uma resposta inflamatória característica da tuberculose. A prolil oligopeptidase de Mycobacterium tuberculosis (rPOPMt) revelou possuir atividade catalítica sobre o substrato N-Suc-Gly-Pro-Leu-Gly-Pro-AMC, com uma atividade ótima a pH 7,5 e temperatura ótima a 28 °C. Aditivos como NaCl, DTT e íons não influenciaram a atividade enzimática da proteína. Os parâmetros cinéticos calculados para a enzima foram Km e kcat/Km de 108 μM e 21.838 mM-1 .s-1, respectivamente, com N-Suc-Gly-Pro-Leu-Gly-Pro-AMC como substrato. ______________________________________________________________________________________________ ABSTRACT

Our group aims to identify and characterize potential targets for chemotherapy for diseases such as Chagas disease, dengue, leishmaniasis and tuberculosis. Proteases are the main focus since they are involved in fundamental biological processes for viability and virulence of pathogens. In this context, this thesis reports some biochemical, structural and functional aspects of the prolyl oligopeptidase of Mycobacterium tuberculosis, the microorganism responsible for triggering an inflammatory response characteristic of tuberculosis. The prolyl oligopeptidase of M. tuberculosis (rPOPMt) showed catalytic activity towards the substrate N-Suc-Gly-Pro-Leu-Gly-Pro-AMC, with optimal pH and temperature activity at 7.5 and 28 °C, respectively. Additives such as NaCl and DTT, and ions did not affect the enzymatic activity of the protein. The kinetic parameters for the enzyme using N-Suc-Gly-Pro-Leu-Gly-Pro-AMC as substrate were calculated showing Km and kcat/km of 108 μM and 21.838 mM-1.s-1, respectively. The enzyme was only susceptible to serine protease inhibitors such as AEBSF and TPCK, with a residual activity of 33 and 66 %, respectively. In presence of Z-Pro-prolinal, a specific inhibitor of prolyl oligopeptidase, a Ki value of 16.87 nM was calculated. Studies of homology modeling and molecular dynamics permitted the achievement of POPMt theoretical structure, and as for other POPs, the structure possess two domains: the catalytic and β-propeller domain, moreover, the catalytic site comprises the triad Ser-Asp-His is conserved along POPs. When the recombinant protein was used in a vaccine formulation with CpG DNA, it was observed a higher level of IgG2a antibody known as a marker for Th1-type immune response. The immunomodulatory properties of POPMt in triggering immune responses in vitro shows that the secretion of cytokines analyzed, TNF-α, IL-6, IL-12p70, IL-23, IL-10, IL-1β and MCP-1 induced by POPMt were largely dependent on the activity of the enzyme. Thus, the recombinant protein can help to determine the role of the native POP in M. tuberculosis.