EC - β-ketoacyl-[acyl-carrier-protein] synthase III

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IntEnz Enzyme Nomenclature


Accepted name:
β-ketoacyl-[acyl-carrier-protein] synthase III
Other names:
3-oxoacyl:ACP synthase III
3-ketoacyl-acyl carrier protein synthase III
β-ketoacyl-acyl carrier protein synthase III
β-ketoacyl-ACP synthase III
β-ketoacyl (acyl carrier protein) synthase III
Systematic name:
acetyl-CoA:malonyl-[acyl-carrier-protein] C-acyltransferase



The enzyme is responsible for initiating straight-chain fatty acid biosynthesis by the dissociated (or type II) fatty-acid biosynthesis system that occurs in plants and bacteria. In contrast to EC, β-ketoacyl-[acyl-carrier-protein] synthase I, and EC, β-ketoacyl-[acyl-carrier-protein] synthase II, this enzyme specifically uses short-chain acyl-CoA thioesters (preferably acetyl-CoA) rather than acyl-[acp] as its substrate [1]. The enzyme can also catalyse the reaction of EC, [acyl-carrier-protein] S-acetyltransferase, but to a much lesser extent [1]. The enzymes from some organisms (e.g. the Gram-positive bacterium Streptococcus pneumoniae) can accept branched-chain acyl-CoAs in addition to acetyl-CoA [5] (cf. EC, branched-chain β-ketoacyl-[acyl-carrier-protein] synthase).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0033818
UniProtKB/Swiss-Prot: (418) [show] [UniProt]


  1. Tsay, J.T., Oh, W., Larson, T.J., Jackowski, S. and Rock, C.O.
    Isolation and characterization of the β-ketoacyl-acyl carrier protein synthase III gene (fabH) from Escherichia coli K-12.
    J. Biol. Chem. 267 : 6807-6814 (1992). [PMID: 1551888]
  2. Han, L., Lobo, S. and Reynolds, K.A.
    Characterization of β-ketoacyl-acyl carrier protein synthase III from Streptomyces glaucescens and its role in initiation of fatty acid biosynthesis.
    J. Bacteriol. 180 : 4481-4486 (1998). [PMID: 9721286]
  3. Khandekar, S.S., Gentry, D.R., Van Aller, G.S., Warren, P., Xiang, H., Silverman, C., Doyle, M.L., Chambers, P.A., Konstantinidis, A.K., Brandt, M., Daines, R.A. and Lonsdale, J.T.
    Identification, substrate specificity, and inhibition of the Streptococcus pneumoniae β-ketoacyl-acyl carrier protein synthase III (FabH).
    J. Biol. Chem. 276 : 30024-30030 (2001). [PMID: 11375394]
  4. Choi, K.H., Kremer, L., Besra, G.S. and Rock, C.O.
    Identification and substrate specificity of β-ketoacyl (acyl carrier protein) synthase III (mtFabH) from Mycobacterium tuberculosis.
    J. Biol. Chem. 275 : 28201-28207 (2000). [PMID: 10840036]
  5. Qiu, X., Choudhry, A.E., Janson, C.A., Grooms, M., Daines, R.A., Lonsdale, J.T. and Khandekar, S.S.
    Crystal structure and substrate specificity of the β-ketoacyl-acyl carrier protein synthase III (FabH) from Staphylococcus aureus.
    Protein Sci. 14 : 2087-2094 (2005). [PMID: 15987898]
  6. Li, Y., Florova, G. and Reynolds, K.A.
    Alteration of the fatty acid profile of Streptomyces coelicolor by replacement of the initiation enzyme 3-ketoacyl acyl carrier protein synthase III (FabH).
    J. Bacteriol. 187 : 3795-3799 (2005). [PMID: 15901703]
  7. Cronan, J.E., Jr. and Rock, C.O.
    Biosynthesis of membrane lipids.
    In: Neidhardt, F.C. (Ed.) Escherichia coli and Salmonella: Cellular and Molecular Biology , 2nd ed. vol. 1 , ASM Press , Washington DC , 1996 , 612-636

[EC created 2006, modified 2021]