M. tuberculosis Acyl CoA Carboxylase 5 complex: crucial metabolic enzyme and attractive target for drug discovery.

GAGO, G.; BAZET LYONNET, B; CABRUJA, M.; DIACOVICH, L.; GRAMAJO, H

Girona

Congreso; Gordon Research Conference Tuberculosis Drug Discovery & Development: Challenges, Advances and Future Prospects in the Fight Against Tuberculosis.; 2015

GRC

Acyl-CoA carboxylases (ACCases) commit acyl-CoAs to the biosynthesis of all the unique lipids present in Mycobacterium tuberculosis cell envelope. M. tuberculosis has several genes coding for ACCase subunits in its genome: three α subunits (accA1?3), six β subunits (accD1?6) and one ε subunit (accE5). However, the physiological roles of the different complexes are still not well defined. Bioinformatic, biochemical and structural analysis of M. tuberculosis ACCase 5 complex indicated that the main catalytic activity of this enzyme corresponds to that of a propionyl-CoA/acetyl-CoA carboxylase. This complex is formed by the biotynilated α subunit AccA3, the carboxyltransferase β subunit AccD5 and the small ε subunit AccE5. To gain insight about the metabolic relevance of this enzyme in mycobacteria, we obtained KO mutants in the genes encoding for the two subunits specifically associated with this complex. In this work, we present the characterization of the ACCase 5 complex of mycobacteria, based on the analysis of an accD5-accE5 conditional mutant generated in M. smegmatis. Our results demonstrate that AccD5 and AccE5 are part of an essential ACCase involved in lipid biosynthesis and that none of the other ACCases present in this bacterium can compensate for the loss of this complex. accD5 and accE5 are both essential for the viability of this bacterium, and this essentiality is directly related to fatty acid and mycolic acid biosynthesis. Altogether, these results suggested that ACCasa 5 is an attractive target for tuberculosis drug discovery. We developed an enzyme-based assay to identify inhibitors of ACCase 5, optimized it for high- throughput screening, and tested against the TB box library from GSK containing 11,000 compounds. We found several promising candidates that inhibit ACCase 5 with different potency and that now need to be analyzed in more detail.