EC - Meromycolic acid 3-oxoacyl-(acyl carrier protein) synthase II

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IntEnz Enzyme Nomenclature


Accepted name:
meromycolic acid 3-oxoacyl-(acyl carrier protein) synthase II
Other name:
β-ketoacyl-acyl carrier protein synthase KasB
Systematic name:
ultra-long-chain di-unsaturated fattyl acyl-[acyl-carrier protein]:malonyl-[acyl-carrier protein] C-acyltransferase (decarboxylating)



The enzyme is part of the fatty acid synthase (FAS) II system of mycobacteria, which extends modified products of the FAS I system, eventually forming meromycolic acids that are incorporated into mycolic acids. Meromycolic acids consist of a long chain, typically 50-60 carbons, which is functionalized by different groups.Two 3-oxoacyl-(acyl carrier protein) synthases function within the FAS II system, encoded by the kasA and kasB genes. The two enzymes share some sequence identity but function independently on separate sets of substrates. KasB differs from KasA [EC, meromycolic acid 3-oxoacyl-(acyl carrier protein) synthase II], by preferring longer substrates (closer to the upper limit), which also contain two double bonds.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB


  1. Schaeffer, M. L., Agnihotri, G., Volker, C., Kallender, H., Brennan, P. J., Lonsdale, J. T.
    Purification and biochemical characterization of the Mycobacterium tuberculosis beta-ketoacyl-acyl carrier protein synthases KasA and KasB.
    J. Biol. Chem. 276 : 47029-47037 (2001). [PMID: 11600501]
  2. Gao, L. Y., Laval, F., Lawson, E. H., Groger, R. K., Woodruff, A., Morisaki, J. H., Cox, J. S., Daffe, M., Brown, E. J.
    Requirement for kasB in Mycobacterium mycolic acid biosynthesis, cell wall impermeability and intracellular survival: implications for therapy.
    Mol. Microbiol. 49 : 1547-1563 (2003). [PMID: 12950920]
  3. Molle, V., Brown, A. K., Besra, G. S., Cozzone, A. J., Kremer, L.
    The condensing activities of the Mycobacterium tuberculosis type II fatty acid synthase are differentially regulated by phosphorylation.
    J. Biol. Chem. 281 : 30094-30103 (2006). [PMID: 16873379]
  4. Bhatt, A., Fujiwara, N., Bhatt, K., Gurcha, S. S., Kremer, L., Chen, B., Chan, J., Porcelli, S. A., Kobayashi, K., Besra, G. S., Jacobs, W. R.
    Deletion of kasB in Mycobacterium tuberculosis causes loss of acid-fastness and subclinical latent tuberculosis in immunocompetent mice.
    Proc. Natl. Acad. Sci. U.S.A. 104 : 5157-5162 (2007). [PMID: 17360388]
  5. Yamada, H., Bhatt, A., Danev, R., Fujiwara, N., Maeda, S., Mitarai, S., Chikamatsu, K., Aono, A., Nitta, K., Jacobs, W. R., Nagayama, K.
    Non-acid-fastness in Mycobacterium tuberculosis ?kasB mutant correlates with the cell envelope electron density.
    Tuberculosis (Edinb) 92 : 351-357 (2012). [PMID: 22516756]
  6. Vilcheze, C., Molle, V., Carrere-Kremer, S., Leiba, J., Mourey, L., Shenai, S., Baronian, G., Tufariello, J., Hartman, T., Veyron-Churlet, R., Trivelli, X., Tiwari, S., Weinrick, B., Alland, D., Guerardel, Y., Jacobs, W. R., Kremer, L.
    Phosphorylation of KasB regulates virulence and acid-fastness in Mycobacterium tuberculosis.
    PLoS Pathog. 10 : e1004115 (2014). [PMID: 24809459]

[EC created 2019]