Characterization of the long-chain acyl-CoA carboxylase of Mycobacterium tuberculosis.

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

Mar del Plata

Congreso; LI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2015

SAIB

The two Fatty Acid Synthase (FAS) systems of the human pathogen Mycobacterium tuberculosis work in concert tosynthesize mycolic acids. FAS I builds a long-chain acyl-CoA (C24-CoA) and FAS II generate a very long-chainfatty acid (meromycolic acid). A long-chain acyl-CoA carboxylase (LCC) activates the C24 acyl-CoA, and the acyl-AMP ligase FadD32 activates the meromycolic acid chain. These two chains are later condensed by Pks13 to yieldthe final mycolic acid. Besides its importance in mycolic acid biosynthesis, there were no conclusive results of thesubunit composition of the acyl-CoA carboxylase responsible to generate the long-chain carboxyacyl-CoA. Previousresults suggested that the subunits AccA3 and AccD4 were part of this LCC complex. Analysis of an accD5-accE5conditional mutant in M. smegmatis allowed us to speculate that the subunits AccD5 and AccE5, that are part a ofwell-characterized propionyl-CoA carboxylase, are also involved in the long-chain acyl-CoA carboxylation. To solvethis issue, we developed an in vitro assay for measuring LCC activity in the presence of its purified subunits. By using this assay we demonstrated that the LCC complex is formed the subunits AccA3, AccD4, AccD5 and AccE5.The specific role of AccD5 and AccE5, and the kinetic characterization of this enzyme complex are now under study.