|Superclasses:||Reactions Classified By Conversion Type → Simple Reactions → Chemical Reactions → Protein-Modification Reactions|
|Reactions Classified By Substrate → Macromolecule Reactions → Protein-Reactions → Protein-Modification Reactions|
EC Number: 126.96.36.199
Enzymes and Genes:
KASI : fabB ( Escherichia coli K-12 substr. MG1655 )
fatty acid synthase : fas ( Mycobacterium tuberculosis H37Rv )
3-oxoacyl-[acyl-carrier-protein] synthase I, chloroplastic : KASI ( Arabidopsis thaliana col )
In Pathway: palmitate biosynthesis II (bacteria and plants)
Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
Most BioCyc compounds have been protonated to a reference pH value of 7.3, and some reactions have been computationally balanced for hydrogen by adding free protons. Please see the PGDB Concepts Guide for more information.
Mass balance status: Balanced.
Enzyme Commission Primary Name: β-ketoacyl-[acyl-carrier-protein] synthase I
Enzyme Commission Synonyms: β-ketoacyl-ACP synthase I, β-ketoacyl synθse, β-ketoacyl-ACP synθse, β-ketoacyl-acyl carrier protein synθse, β-ketoacyl-[acyl carrier protein] synthase, β-ketoacylsynthase, condensing enzyme, 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)
Standard Gibbs Free Energy (ΔrG'° in kcal/mol): -6.862915 [Latendresse13]
Enzyme Commission Summary:
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) [DAgnolo75]. The substrate specificity is very similar to that of EC 188.8.131.52, 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 [DAgnolo75, Garwin80].
Cronan96: Cronan JE Jr., Rock CO (1996). "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, pp. 612-636.
Garwin80: Garwin JL, Klages AL, Cronan JE (1980). "Structural, enzymatic, and genetic studies of beta-ketoacyl-acyl carrier protein synthases I and II of Escherichia coli." J Biol Chem 1980;255(24);11949-56. PMID: 7002930
Toomey66a: Toomey RE, Wakil SJ (1966). "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(5);1159-65. PMID: 5327099
Wang04a: Wang H, Cronan JE (2004). "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(33);34489-95. PMID: 15194690
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