The Enzyme Database

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Accepted name: β-ketoacyl-[acyl-carrier-protein] synthase I
Reaction: an acyl-[acyl-carrier protein] + a malonyl-[acyl-carrier protein] = a 3-oxoacyl-[acyl-carrier protein] + CO2 + an [acyl-carrier protein]
Glossary: acyl-[acyl-carrier protein] = R-CO-[acyl-carrier protein]
malonyl-[acyl-carrier protein] = HOOC-CH2-CO-[acyl-carrier protein]
3-oxoacyl-[acyl-carrier protein] = R-CO-CH2-CO-[acyl-carrier protein]
Other name(s): β-ketoacyl-ACP synthase I; β-ketoacyl synthetase; β-ketoacyl-ACP synthetase; β-ketoacyl-acyl carrier protein synthetase; β-ketoacyl-[acyl carrier protein] synthase; β-ketoacylsynthase; condensing enzyme (ambiguous); 3-ketoacyl-acyl carrier protein synthase; fatty acid condensing enzyme; acyl-malonyl(acyl-carrier-protein)-condensing enzyme; acyl-malonyl acyl carrier protein-condensing enzyme; β-ketoacyl acyl carrier protein synthase; 3-oxoacyl-[acyl-carrier-protein] synthase; 3-oxoacyl:ACP synthase I; KASI; KAS I; FabF1; FabB; acyl-[acyl-carrier-protein]:malonyl-[acyl-carrier-protein] C-acyltransferase (decarboxylating)
Systematic name: acyl-[acyl-carrier protein]:malonyl-[acyl-carrier protein] C-acyltransferase (decarboxylating)
Comments: This enzyme is responsible for the chain-elongation step of dissociated (type II) fatty-acid biosynthesis, i.e. the addition of two C atoms to the fatty-acid chain. Escherichia coli mutants that lack this enzyme are deficient in unsaturated fatty acids. The enzyme can use fatty acyl thioesters of ACP (C2 to C16) as substrates, as well as fatty acyl thioesters of Co-A (C4 to C16) [4]. The substrate specificity is very similar to that of EC, β-ketoacyl-ACP synthase II, with the exception that the latter enzyme is far more active with palmitoleoyl-ACP (C16Δ9) as substrate, allowing the organism to regulate its fatty-acid composition with changes in temperature [4,5].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9077-10-5
1.  Alberts, A.W., Majerus, P.W. and Vagelos, P.R. Acetyl-CoA acyl carrier protein transacylase. Methods Enzymol. 14 (1969) 50–53. [DOI]
2.  Prescott, D.J. and Vagelos, P.R. Acyl carrier protein. Adv. Enzymol. Relat. Areas Mol. Biol. 36 (1972) 269–311. [DOI] [PMID: 4561013]
3.  Toomey, R.E. and Wakil, S.J. Studies on the mechanism of fatty acid synthesis. XVI. Preparation and general properties of acyl-malonyl acyl carrier protein-condensing enzyme from Escherichia coli. J. Biol. Chem. 241 (1966) 1159–1165. [PMID: 5327099]
4.  D'Agnolo, G., Rosenfeld, I.S. and Vagelos, P.R. Multiple forms of β-ketoacyl-acyl carrier protein synthetase in Escherichia coli. J. Biol. Chem. 250 (1975) 5289–5294. [PMID: 237914]
5.  Garwin, J.L., Klages, A.L. and Cronan, J.E., Jr.. Structural, enzymatic, and genetic studies of β-ketoacyl-acyl carrier protein synthases I and II of Escherichia coli. J. Biol. Chem. 255 (1980) 11949–11956. [PMID: 7002930]
6.  Wang, H. and Cronan, J.E. Functional replacement of the FabA and FabB proteins of Escherichia coli fatty acid synthesis by Enterococcus faecalis FabZ and FabF homologues. J. Biol. Chem. 279 (2004) 34489–34495. [DOI] [PMID: 15194690]
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 edn, vol. 1, ASM Press, Washington, DC, 1996, pp. 612–636.
[EC created 1972, modified 2006]

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