MetaCyc Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical ReactionsProtein-Modification Reactions
Reactions Classified By SubstrateMacromolecule ReactionsProtein-ReactionsProtein-Modification Reactions

EC Number:,,

Enzymes and Genes:

Enterococcus faecalis: 3-hydroxyacyl-[acyl-carrier-protein] dehydratase/isomeraseInferred from experiment: fabN
Escherichia coli K-12 substr. MG1655: β-hydroxyacyl-ACP dehydratase/isomeraseInferred from experiment: fabA
3-hydroxy-acyl-[acyl-carrier-protein] dehydrataseInferred from experiment: fabZ
Homo sapiens: fatty acid synthaseInferred from experiment: FASN
Mycobacterium tuberculosis H37Rv: fatty acid synthase: fas
Saccharomyces cerevisiae: fatty acid synthase, β subunit: FAS1
Spinacia oleracea: 3-hydroxyacyl-[acp] dehydraseInferred from experiment

In Pathway: palmitate biosynthesis I (animals and fungi), palmitate biosynthesis II (bacteria and plants), (5Z)-dodec-5-enoate biosynthesis

Supersedes EC numbers:,,

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.

Mass balance status: Balanced.

Direct generic reaction:
a (3R)-3-hydroxyacyl-[acyl-carrier protein] → a trans-2-enoyl-[acyl-carrier protein] + H2O (

Enzyme Commission Primary Name for fatty-acid synthase

Enzyme Commission Synonyms for FASN (gene name)

Enzyme Commission Primary Name for fatty-acyl-CoA synthase

Enzyme Commission Synonyms for yeast fatty acid synthase, FAS1 (gene name), FAS2 (gene name)

Enzyme Commission Primary Name for 3-hydroxyacyl-[acyl-carrier-protein] dehydratase

Enzyme Commission Synonyms for fabZ (gene name), fabA (gene name), D-3-hydroxyoctanoyl-[acyl carrier protein] dehydratase, D-3-hydroxyoctanoyl-acyl carrier protein dehydratase, β-hydroxyoctanoyl-acyl carrier protein dehydrase, β-hydroxyoctanoyl thioester dehydratase, β-hydroxyoctanoyl-ACP-dehydrase, (3R)-3-hydroxyoctanoyl-[acyl-carrier-protein] hydro-lyase, (3R)-3-hydroxyoctanoyl-[acyl-carrier-protein] hydro-lyase (oct-2-enoyl-[acyl-carrier protein]-forming), 3-hydroxyoctanoyl-[acyl-carrier-protein] dehydratase

Standard Gibbs Free Energy (ΔrG in kcal/mol): 22.705246Inferred by computational analysis [Latendresse13]

This enzyme is different from EC, since the later is specific for C10 chain length, and is used in the synthesis of unsaturated fatty acids, while this enzyme accepts a broad substrate range and is used in the synthesis of saturated fatty acids.

Enzyme Commission Summary for
The animal enzyme is a multi-functional protein catalysing the reactions of EC, [acyl-carrier-protein] S-acetyltransferase, EC, [acyl-carrier-protein] S-malonyltransferase, EC, β-ketoacyl-[acyl-carrier-protein] synthase I, EC, 3-oxoacyl-[acyl-carrier-protein] reductase, EC, 3-hydroxyacyl-[acyl-carrier-protein] dehydratase, EC, enoyl-[acyl-carrier-protein] reductase (NADPH, Re-specific) and EC, oleoyl-[acyl-carrier-protein] hydrolase. cf. EC, fatty-acyl-CoA synthase.

Enzyme Commission Summary for
The enzyme from yeasts ( Ascomycota and Basidiomycota) is a multi-functional protein complex composed of two subunits. One subunit catalyses the reactions EC, 3-oxoacyl-[acyl-carrier-protein] reductase and EC, β-ketoacyl-[acyl-carrier-protein] synthase I, while the other subunit catalyses the reactions of EC, [acyl-carrier-protein] S-acetyltransferase, EC, [acyl-carrier-protein] S-malonyltransferase, EC, 3-hydroxyacyl-[acyl-carrier-protein] dehydratase, EC, enoyl-[acyl-carrier-protein] reductase (NADPH, Si-specific) and EC, (R)-3-hydroxyacid-ester dehydrogenase. The enzyme differs from the animal enzyme ( EC in that the enoyl reductase domain requires FMN as a cofactor, and the ultimate product is an acyl-CoA (usually palmitoyl-CoA) instead of a free fatty acid.

Enzyme Commission Summary for
This enzyme is responsible for the dehydration step of the dissociated (type II) fatty-acid biosynthesis system that occurs in plants and bacteria. The enzyme uses fatty acyl thioesters of ACP in vivo. Different forms of the enzyme may have preferences for substrates with different chain length. For example, the activity of FabZ, the ubiquitous enzyme in bacteria, decreases with increasing chain length. Gram-negative bacteria that produce unsaturated fatty acids, such as Escherichia coli, have another form (FabA) that prefers intermediate chain length, and also catalyses EC, trans-2-decenoyl-[acyl-carrier protein] isomerase. Despite the differences both forms can catalyse all steps leading to the synthesis of palmitate (C16:0). FabZ, but not FabA, can also accept unsaturated substrates [Heath96].

Citations: [Stoops79, Wakil83, Schweizer73, Tehlivets07, Mizugaki68, Sharma90, Mohan94]

Gene-Reaction Schematic

Gene-Reaction Schematic

Instance reaction of [a (3R)-3-hydroxyacyl-[acyl-carrier protein] → a trans-2-enoyl-[acyl-carrier protein] + H2O] (
i1: a (3R)-3-hydroxydecanoyl-[acp] → a (2E)-dec-2-enoyl-[acp] + H2O (



Heath96: Heath RJ, Rock CO (1996). "Roles of the FabA and FabZ beta-hydroxyacyl-acyl carrier protein dehydratases in Escherichia coli fatty acid biosynthesis." J Biol Chem 1996;271(44);27795-801. PMID: 8910376

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Mizugaki68: Mizugaki M, Swindell AC, Wakil SJ (1968). "Intermediate- and long-chain beta-hydroxyacyl-ACP dehydrases from E. coli fatty acid synthetase." Biochem Biophys Res Commun 33(3);520-7. PMID: 4881058

Mohan94: Mohan S, Kelly TM, Eveland SS, Raetz CR, Anderson MS (1994). "An Escherichia coli gene (FabZ) encoding (3R)-hydroxymyristoyl acyl carrier protein dehydrase. Relation to fabA and suppression of mutations in lipid A biosynthesis." J Biol Chem 1994;269(52);32896-903. PMID: 7806516

Schweizer73: Schweizer E, Kniep B, Castorph H, Holzner U (1973). "Pantetheine-free mutants of the yeast fatty-acid-synthetase complex." Eur J Biochem 39(2);353-62. PMID: 4590449

Sharma90: Sharma A, Henderson BS, Schwab JM, Smith JL (1990). "Crystallization and preliminary X-ray analysis of beta-hydroxydecanoyl thiol ester dehydrase from Escherichia coli." J Biol Chem 1990;265(9);5110-2. PMID: 2180957

Stoops79: Stoops JK, Ross P, Arslanian MJ, Aune KC, Wakil SJ, Oliver RM (1979). "Physicochemical studies of the rat liver and adipose fatty acid synthetases." J Biol Chem 254(15);7418-26. PMID: 457689

Tehlivets07: Tehlivets O, Scheuringer K, Kohlwein SD (2007). "Fatty acid synthesis and elongation in yeast." Biochim Biophys Acta 1771(3);255-70. PMID: 16950653

Wakil83: Wakil SJ, Stoops JK, Joshi VC (1983). "Fatty acid synthesis and its regulation." Annu Rev Biochem 52;537-79. PMID: 6137188

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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