Reaction: an ultra-long-chain mono-unsaturated acyl-[acyl-carrier protein] + a malonyl-[acyl-carrier protein] = an ultra-long-chain mono-unsaturated 3-oxo-fatty acyl-[acp] + CO2 + an [acyl-carrier protein]
Other name(s): kasA (gene name); β-ketoacyl-acyl carrier protein synthase KasA
Systematic name: ultra-long-chain mono-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. KasA differs from KasB (EC 220.127.116.114), by preferring shorter (C-22 to C-36) and more saturated (only one double bond) substrates.
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. Bhatt, A., Kremer, L., Dai, A.Z., Sacchettini, J.C. and Jacobs, W.R., Jr. Conditional depletion of KasA, a key enzyme of mycolic acid biosynthesis, leads to mycobacterial cell lysis. J. Bacteriol. 187 (2005) 7596-7606. [PMID: 16267284]
3. Luckner, S.R., Machutta, C.A., Tonge, P.J. and Kisker, C. Crystal structures of Mycobacterium tuberculosis KasA show mode of action within cell wall biosynthesis and its inhibition by thiolactomycin. Structure 17 (2009) 1004-1013. [PMID: 19604480]