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The Two Carboxylases of Corynebacterium glutamicum Essential for Fatty Acid and Mycolic Acid Synthesis ^,

Institute for Biotechnology, Research Centre Juelich, D-52425 Juelich, Germany,¹ School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom,² Kansai University High Technology Research Center, Suita-shi, Osaka 564-8680, Japan³

Received 14 February 2007/ Accepted 29 April 2007

The suborder Corynebacterianeae comprises bacteria like Mycobacterium tuberculosis and Corynebacterium glutamicum, and these bacteria contain in addition to the linear fatty acids, unique -branched ß-hydroxy fatty acids, called mycolic acids. Whereas acetyl-coenzyme A (CoA) carboxylase activity is required to provide malonyl-CoA for fatty acid synthesis, a new type of carboxylase is apparently additionally present in these bacteria. It activates the -carbon of a linear fatty acid by carboxylation, thus enabling its decarboxylative condensation with a second fatty acid to afford mycolic acid synthesis. We now show that the acetyl-CoA carboxylase of C. glutamicum consists of the biotinylated -subunit AccBC, the ß-subunit AccD1, and the small peptide AccE of 8.9 kDa, forming an active complex of approximately 812,000 Da. The carboxylase involved in mycolic acid synthesis is made up of the two highly similar ß-subunits AccD2 and AccD3 and of AccBC and AccE, the latter two identical to the subunits of the acetyl-CoA carboxylase complex. Since AccD2 and AccD3 orthologues are present in all Corynebacterianeae, these polypeptides are vital for mycolic acid synthesis forming the unique hydrophobic outer layer of these bacteria, and we speculate that the two ß-subunits present serve to lend specificity to this unique large multienzyme complex.

Published ahead of print on 4 May 2007.

Supplemental material for this article is available at http://jb.asm.org/.

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