CHARACTERIZATION OF A GROUP OF ACYL-COA CARBOXILASES FROM MYCOBACTERIUM TUBERCULOSIS

KURTH, D; GAGO, G; GRAMAJO, H

Iguazú, Misiones, Argentina.

Congreso; XL Annual Meeting of the Argentinean Society for Biochemistry and Molecular Biology (SAIB); 2004

SAIB

Acyl-CoA carboxylases are key enzymes for the synthesis of lipids in actinomycetes, as they provide the elongating units malonyl- and methylmalonyl-CoA. We characterized two acyl-CoA carboxylases complexes in Streptomyces coelicolor. They consist of an alpha subunit with the ability to carboxylate its covalently bound biotin group, a beta subunit bearing the carboxyl transferase activity and a small epsilon subunit. In M. tuberculosis three complete carboxylase systems could be found, each consisting of an alpha-(AccA) and a beta-(AccD) subunit, as well as three beta subunits without an alpha counterpart. There is also an ORF (Rv 3281) associated with the beta subunit AccD5 that codes for a putative epsilon subunit. Here we present the biochemical and structural characterization of a group of essential acyl-CoA carboxylases from M. tuberculosis. Three acyl-CoA carboxylases have been successfully reconstituted from their purified components. The three complexes consist of a specific beta subunit (AccD4, AccD5, and AccD6) and share the same biotinylated alpha subunit (AccA3) and epsilon subunit (AccE5). For all complexes the addition of AccE5 dramatically increased the specific activity of the enzymes. Also, all complexes were able to carboxylate both acetyl and propionyl-CoA, although a clear preference for propionyl-CoA was evident. This is the first report of the presence of a functional epsilon subunit in M. tuberculosis. These studies aim to provide a novel drug design target for tuberculosis.