EC 2.3.1.294     
Accepted name: meromycolic acid 3-oxoacyl-(acyl carrier protein) synthase II
Reaction: an ultra-long-chain di-unsaturated acyl-[acyl-carrier protein] + a malonyl-[acyl-carrier protein] = an ultra-long-chain di-unsaturated 3-oxo-fatty acyl-[acyl-carrier protein] + CO2 + a holo-[acyl-carrier protein]
Other name(s): kasB (gene 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)
Comments: 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 2.3.1.293, meromycolic acid 3-oxoacyl-(acyl carrier protein) synthase I), by preferring longer substrates (closer to the upper limit), which also contain two double bonds.
References:
1.  Schaeffer, M.L., Agnihotri, G., Volker, C., Kallender, H., Brennan, P.J. and Lonsdale, J.T. Purification and biochemical characterization of the Mycobacterium tuberculosis β-ketoacyl-acyl carrier protein synthases KasA and KasB. J. Biol. Chem. 276 (2001) 47029–47037. [PMID: 11600501]
2.  Gao, L.Y., Laval, F., Lawson, E.H., Groger, R.K., Woodruff, A., Morisaki, J.H., Cox, J.S., Daffe, M. and Brown, E.J. Requirement for kasB in Mycobacterium mycolic acid biosynthesis, cell wall impermeability and intracellular survival: implications for therapy. Mol. Microbiol. 49 (2003) 1547–1563. [PMID: 12950920]
3.  Molle, V., Brown, A.K., Besra, G.S., Cozzone, A.J. and Kremer, L. The condensing activities of the Mycobacterium tuberculosis type II fatty acid synthase are differentially regulated by phosphorylation. J. Biol. Chem. 281 (2006) 30094–30103. [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. and Jacobs, W.R., Jr. Deletion of kasB in Mycobacterium tuberculosis causes loss of acid-fastness and subclinical latent tuberculosis in immunocompetent mice. Proc. Natl. Acad. Sci. USA 104 (2007) 5157–5162. [PMID: 17360388]
5.  Yamada, H., Bhatt, A., Danev, R., Fujiwara, N., Maeda, S., Mitarai, S., Chikamatsu, K., Aono, A., Nitta, K., Jacobs, W.R., Jr. and Nagayama, K. Non-acid-fastness in Mycobacterium tuberculosis Δ kasB mutant correlates with the cell envelope electron density. Tuberculosis (Edinb) 92 (2012) 351–357. [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., Jr. and Kremer, L. Phosphorylation of KasB regulates virulence and acid-fastness in Mycobacterium tuberculosis. PLoS Pathog. 10:e1004115 (2014). [PMID: 24809459]
[EC 2.3.1.294 created 2019]