. Characterization of the acyl-CoA carboxylases of Mycobacterium tuberculosis.

BAZET LYONNET, B., DIACOVICH, L., GAGO, G. AND GRAMAJO, H

Congreso; SAIB; 2014

CHARACTERIZATION OF THE ACYL- COENZYME A CARBOXYLASES OF MYCOBACTERIUM TUBERCULOSISBazet Lyonnet, B., Diacovich, L., Gago, G. and Gramajo, H. IBR, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Rosario. E-mail: bazetlyonnet@ibr-conicet.gov.arCaracteres: 1365The two Fatty Acid Sinthase (FAS) systems of the human pathogen M. tuberculosis work together to synthesize mycolic acids. FAS I build a long chain acyl-CoA (C24-CoA) and FAS II generate a very long fatty acid chain (meromycolic acid). A long chain acyl-CoA carboxylase activates the C24 acyl-CoA, and the acyl-AMP ligase FadD32 activates the meromycolic acid chain. These two chains are later condensated by Pks13 to yield the final mycolic acid. However its importance in mycolic acid biosynthesis, there are no conclusive results of the subunit composition of the acyl-CoA carboxylase responsible to generate the long-chain carboxyacyl-CoA. We found that an accD5-accE5 conditional mutant in M. smegmatis has a deficiency in the long chain acyl-CoA carboxylase activity and less long chain carboxyacyl-CoA pools. Also, 14C-acetate labeling and TLC analysis of FAMEs and MAMEs of this mutant showed an accumulation of a previously uncharacterized spot, that it is composed of meromycolic acids methyl esters. These results allow us to speculate that the subunits AccD5 and AccE5, that forms a well-characterized propionyl-CoA carboxylase, are also involved in the long chain acyl-CoA carboxylation. To solve this issue, we performed in vitro assays and we found evidences that the subunits AccD5 and AccE5 are part of the active long chain acyl-CoA carboxylase.