Mycobacterial beta-ketoacyl-[acyl-carrier-protein] synthase III

UniProtKB accession:  P9WNG3

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UniProtKB description:  Catalyzes the condensation reaction of fatty acid synthesis by the addition to an acyl acceptor of two carbons from malonyl-ACP. Catalyzes the first condensation reaction which initiates fatty acid synthesis and may therefore play a role in governing the total rate of fatty acid production. Possesses both acetoacetyl-ACP synthase and acetyl transacylase activities (PubMed:10840036, PubMed:11278743, PubMed:16040614). Possesses a clear preference for long-chain acyl-CoA substrates rather than acyl-ACP primers. Its substrate specificity determines the biosynthesis of mycolic acid fatty acid chain, which is characteristic of mycobacterial cell wall (PubMed:10840036, PubMed:11278743, PubMed:16040614). In vitro, when AcpM (the natural partner) is used as the carrier, malonate incorporation increases with acyl chain length to reach an apparent maximum with primers ranging in length from C:14-CoA to C:20-CoA (PubMed:16040614). However, the initial acylation step shows preference for dodecanoyl-CoA, suggesting a role for AcpM in determining the specificity of the mtFabH reaction (PubMed:18096200). Shows only very weak activity with acetyl-CoA (PubMed:10840036, PubMed:11278743).