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Information on EC 2.3.1.300 - branched-chain beta-ketoacyl-[acyl-carrier-protein] synthase
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EC Tree
2.3.1.300 branched-chain beta-ketoacyl-[acyl-carrier-protein] synthaseIUBMB Comments
The enzyme is responsible for initiating branched-chain fatty acid biosynthesis by the dissociated (or type II) fatty-acid biosynthesis system (FAS-II) in some bacteria, using molecules derived from degradation of the branched-chain amino acids L-leucine, L-valine, and L-isoleucine to form the starting molecules for elongation by the FAS-II system. In some organisms the enzyme is also able to use acetyl-CoA, leading to production of a mix of branched-chain and straight-chain fatty acids (cf. EC 2.3.1.180, beta-ketoacyl-[acyl-carrier-protein] synthase III).
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The enzyme appears in viruses and cellular organisms
Reaction Schemes
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a 5-methyl-3-oxohexanoyl-[acyl-carrier-protein]
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a 4-methyl-3-oxopentanoyl-[acyl-carrier-protein]
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a (4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein]
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Synonyms
3-oxoacyl-[acyl-carrier-protein] synthase, FabH, FabH1, FabH2, FabHA, FabHB, KAS III, LMRG_01630, 
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
FabH
FabH1
FabH2
FabHA
FabHB
KAS III
LMRG_01630
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
(2S)-2-methylbutanoyl-CoA + a malonyl-[acyl-carrier protein] = a (4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
(3)
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2-methylpropanoyl-CoA + a malonyl-[acyl-carrier protein] = a 4-methyl-3-oxopentanoyl-[acyl-carrier-protein] + CoA + CO2
(2)
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3-methylbutanoyl-CoA + a malonyl-[acyl-carrier protein] = a 5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
(1)
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PATHWAY SOURCE
PATHWAYS
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SYSTEMATIC NAME
IUBMB Comments
3-methylbutanoyl-CoA:malonyl-[acyl-carrier protein] C-acyltransferase
The enzyme is responsible for initiating branched-chain fatty acid biosynthesis by the dissociated (or type II) fatty-acid biosynthesis system (FAS-II) in some bacteria, using molecules derived from degradation of the branched-chain amino acids L-leucine, L-valine, and L-isoleucine to form the starting molecules for elongation by the FAS-II system. In some organisms the enzyme is also able to use acetyl-CoA, leading to production of a mix of branched-chain and straight-chain fatty acids [3] (cf. EC 2.3.1.180, beta-ketoacyl-[acyl-carrier-protein] synthase III).
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
(2S)-2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
(4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
2-methylpropanoyl-CoA + malonyl-[acyl-carrier protein]
4-methyl-3-oxopentanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
3-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
ethyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
acetyl-CoA + malonyl-[acyl-carrier protein]
3-oxobutanoyl-[acyl-carrier protein] + CoA + CO2
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-
-
?
butanoyl-CoA + malonyl-[acyl-carrier protein]
3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
isobutanoyl-CoA + malonyl-[FabC]
5-methyl-3-oxohexanoyl-[FabC] + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[RedQ]
5-methyl-3-oxohexanoyl-[RedQ] + CoA + CO2
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malonyl-[RedQ] is involved in undecylprodiginine biosynthesis
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-
?
(2S)-2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
(4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
(2S)-2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
(4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
(2S)-2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
(4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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-
-
?
isohexanoyl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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-
-
?
isohexanoyl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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-
?
isovaleryl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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?
isovaleryl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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?
isovaleryl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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?
isovaleryl-CoA + malonyl-[acyl-carrier protein]
? + CoA + CO2
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?
additional information
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KAS III has distinctive substrate specificity and uses branched-chain acyl-CoA as well as long-chain acyl-CoA. KAS III can use butanoyl-, isobutanoyl-, and hexanoyl-CoA as preferred substrates over acetyl-CoA (reaction of EC 32.3.1.180)
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additional information
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KAS III has distinctive substrate specificity and uses branched-chain acyl-CoA as well as long-chain acyl-CoA. KAS III can use butanoyl-, isobutanoyl-, and hexanoyl-CoA as preferred substrates over acetyl-CoA (reaction of EC 32.3.1.180)
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additional information
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the order of catalytic efficiency (in decreasing order) is: 2-methylbutyryl-CoA, isovaleryl-CoA, isobutyryl-CoA, acetyl-CoA
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additional information
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the order of catalytic efficiency (in decreasing order) is: 2-methylbutyryl-CoA, isovaleryl-CoA, isobutyryl-CoA, acetyl-CoA
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additional information
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enzyme demonstrates both beta-ketoacyl-acyl carrier protein synthase activity and acyl coenzyme A:acyl carrier protein transacylase activity in a 1:0.12 ratio
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additional information
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FabH in addition uses acetyl-CoA, butanoyl-CoA, hexanoyl-CoA, octanoyl-CoA, or decanoyl-CoA as a primer as a primer to initiate fatty acid synthesis, reaction of EC 2.3.1.180, and also condenses short-chain acyl-ACPs with malonyl-ACP to produce longer acyl-ACPs
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
(2S)-2-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
(4S)-4-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
2-methylpropanoyl-CoA + malonyl-[acyl-carrier protein]
4-methyl-3-oxopentanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
3-methylbutanoyl-CoA + malonyl-[acyl-carrier protein]
ethyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
acetyl-CoA + malonyl-[acyl-carrier protein]
3-oxobutanoyl-[acyl-carrier protein] + CoA + CO2
-
-
-
?
butanoyl-CoA + malonyl-[acyl-carrier protein]
3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
isobutanoyl-CoA + malonyl-[acyl-carrier protein]
5-methyl-3-oxohexanoyl-[acyl-carrier-protein] + CoA + CO2
-
-
-
?
additional information
?
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enzyme demonstrates both beta-ketoacyl-acyl carrier protein synthase activity and acyl coenzyme A:acyl carrier protein transacylase activity in a 1:0.12 ratio
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
11350
substrate isobutanoyl-CoA, pH 7, temperature not specified in the publication
17350
substrate isovaleryl-CoA, pH 7, temperature not specified in the publication
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
physiological function
physiological function
FabH is able to condense branched-chain acyl-CoAs with malonyl-ACP to initiate branched-chain fatty acid synthesis. The fabH gene is essential for growth of Xanthomonas campestris. It can be replaced with Escherichia coli fabH, and transgenic strains mutants fail to produce branched-chain fatty acids. Xanthomonas campestris FabH mutants lost the ability to produce cis-11-methyl-2-dodecenoic acid
physiological function
FabH is responsible for initiating both straight- and branched-chain fatty acid biosynthesis in Streptomyces glaucescens and the ratio of the various fatty acids produced will be dictated by the ratios of the various acyl-CoA substrates that can react with FabH
physiological function
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replacement of the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Staphylococcus aureus FabH increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs
physiological function
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replacementof the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Bacillus subtilis FabH1 increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs
physiological function
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replacementof the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Bacillus subtilis FabH2 increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs
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UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable).
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable). C0LNR0_LISM4
Listeria monocytogenes serotype 1/2a (strain 10403S)
312
0
33971
TrEMBL
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FABH_XANC8
Xanthomonas campestris pv. campestris (strain 8004)
325
0
34692
Swiss-Prot
-
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
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PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
C122A
C122A
mutation of active-site residue, mutant displays much improved solubility
C122A
-
mutation of active-site residue, mutant displays much improved solubility
-
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CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
expression in Escherichia coli
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
synthesis
synthesis
-
replacement of the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Bacillus subtilis FabH1 increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs. The titer of branched-chain fatty acids reaches 19.4 mg/L. The composition of branched-chain fatty acids can be tuned by engineering the upstream pathway to control the supply of different branched-chain acyl-CoAs, leading to the production either even-chain-iso-, odd-chain-iso-, or odd-chain-anteiso-branched-chain fatty acids separately
synthesis
-
replacement of the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Bacillus subtilis FabH2 increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs. The titer of branched-chain fatty acids reaches 17.5 mg/L. The composition of branched-chain fatty acids can be tuned by engineering the upstream pathway to control the supply of different branched-chain acyl-CoAs, leading to the production either even-chain-iso-, odd-chain-iso-, or odd-chain-anteiso-branched-chain fatty acids separately
synthesis
-
replacement of the acetyl-CoA-specific Escherichia coli FabH with branched-chain-acyl-CoA-specific Staphylococcus aureus FabH increases the synthesis of branched-chain fatty acids, resulting in a significant enhancement in branched-chain fatty acids titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs. The titer of branched-chain fatty acids reaches 40.3 mg/L. The composition of branched-chain fatty acids can be tuned by engineering the upstream pathway to control the supply of different branched-chain acyl-CoAs, leading to the production either even-chain-iso-, odd-chain-iso-, or odd-chain-anteiso-branched-chain fatty acids separately
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REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Cheon, D.; Lee, W.; Lee, Y.; Lee, J.; Kim, Y.
Structural basis of branched-chain fatty acid synthesis by Propionibacterium acnes beta-ketoacyl acyl carrier protein synthase
Biochem. Biophys. Res. Commun.
509
322-328
2019
Cutibacterium acnes (A0A2B7IGT3), Cutibacterium acnes KPA171202 (A0A2B7IGT3)
brenda
Jiang, W.; Jiang, Y.; Bentley, G.; Liu, D.; Xiao, Y.; Zhang, F.
Enhanced production of branched-chain fatty acids by replacing beta-ketoacyl-(acyl-carrier-protein) synthase III (FabH)
Biotechnol. Bioeng.
112
1613-1622
2015
Bacillus subtilis, Staphylococcus aureus
brenda
Singh, A.; Zhang, Y.; Zhu, K.; Subramanian, C.; Li, Z.; Jayaswal, R.; Gatto, C.; Rock, C.; Wilkinson, B.
FabH selectivity for anteiso branched-chain fatty acid precursors in low-temperature adaptation in Listeria monocytogenes
FEMS Microbiol. Lett.
301
188-192
2009
Listeria monocytogenes serotype 1/2a (C0LNR0), Listeria monocytogenes serotype 1/2a 10403S (C0LNR0)
brenda
Singh, R.; Mo, S.; Florova, G.; Reynolds, K.
Streptomyces coelicolor RedP and FabH enzymes, initiating undecylprodiginine and fatty acid biosynthesis, exhibit distinct acyl-CoA and malonyl-acyl carrier protein substrate specificities
FEMS Microbiol. Lett.
328
32-38
2012
Streptomyces coelicolor
brenda
Han, L.; Lobo, S.; Reynolds, K.
Characterization of beta-ketoacyl-acyl carrier protein synthase III from Streptomyces glaucescens and its role in initiation of fatty acid biosynthesis
J. Bacteriol.
180
4481-4486
1998
Streptomyces glaucescens (Q54206)
brenda
Choi, K.; Heath, R.; Rock, C.
beta-Ketoacyl-acyl carrier protein synthase III (FabH) is a determining factor in branched-chain fatty acid biosynthesis
J. Bacteriol.
182
365-370
2000
Bacillus subtilis (O07600), Bacillus subtilis (O34746), Bacillus subtilis 168 (O07600), Bacillus subtilis 168 (O34746)
brenda
Yu, Y.; Hu, Z.; Dong, H.; Ma, J.; Wang, H.
Xanthomonas campestris FabH is required for branched-chain fatty acid and DSF-family quorum sensing signal biosynthesis
Sci. Rep.
6
32811
2016
Xanthomonas campestris pv. campestris (Q4URQ0)
brenda
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Release 2023.1 (January 2023)
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