In vitro reconstitution of the complete mycolic acid condensation system of Mycobacterium tuberculosis

BAZET LYONNET B, BARDOU F, QUÉMARD A, DAFFÉ M, GAGO G , GRAMAJO, H

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2012

SAIB

Mycolic acids are essential for the survival, virulence and antibiotic resistance of the human pathogen Mycobacterium tuberculosis. In mycobacteria, the acyl-CoA carboxylases (ACCases) provide carboxyacyl-CoAs, the building blocks for de novo fatty acid and mycolic acid biosynthesis. Malonyl-CoA is produced by ACCase 6 and is necessary for both fatty acid and mycolic acid biosynthesis. Mycolic acid is synthesized by the condensation of a long-chain carboxyacyl-CoA and a meromycolil-AMP by Pks13. So far, there are no conclusive results on the subunit composition of the ACCase responsible to generate the long-chain carboxyacyl-CoA. To solve this issue, we performed an in vitro assay in which we mixed different ACCase subunits together with the enzymes FadD32 and Pks13, and looked for the condensation products. We found that the subunits AccA3, AccD4, AccD5 and AccE5 form the active ACCase that generates the long-chain carboxyacyl-CoA. Furthermore, by generating an accD5 conditional mutant in M. smegmatis we demonstrated that accD5 is essential in this bacterium, and is necessary for optimal levels of mycolic acid biosynthesis. These results propose AccD5 as a good target for the development of novel antimycobacterial drugs.