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
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).
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)
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)
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
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
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
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
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
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
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
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
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
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
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
Characterization of beta-ketoacyl-acyl carrier protein synthase III from Streptomyces glaucescens and its role in initiation of fatty acid biosynthesis