Long-chain-fatty-acid—CoA ligase | |||||||||
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![]() Long chain fatty acyl-CoA synthetase homodimer from Thermus thermophilus . [1] | |||||||||
Identifiers | |||||||||
EC no. | 6.2.1.3 | ||||||||
CAS no. | 9013-18-7 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
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acyl-CoA synthetase long-chain family member 1 | |||||||
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Identifiers | |||||||
Symbol | ACSL1 | ||||||
Alt. symbols | FACL2 | ||||||
NCBI gene | 2180 | ||||||
HGNC | 3569 | ||||||
OMIM | 152425 | ||||||
RefSeq | NM_001995 | ||||||
UniProt | P33121 | ||||||
Other data | |||||||
EC number | 6.2.1.3 | ||||||
Locus | Chr. 4 q35 | ||||||
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The long chain fatty acyl-CoA ligase (or synthetase) is an enzyme (EC 6.2.1.3) of the ligase family that activates the oxidation of complex fatty acids. [2] Long chain fatty acyl-CoA synthetase catalyzes the formation of fatty acyl-CoA by a two-step process proceeding through an adenylated intermediate. [3] The enzyme catalyzes the following reaction,
It is present in all organisms from bacteria to humans. It catalyzes the pre-step reaction for β-oxidation of fatty acids or can be incorporated in phospholipids.
Long chain fatty acyl-CoA synthetase, LC-FACS, plays a role in the physiological regulation of various cellular functions via the production of long chain fatty acyl-CoA esters, which reportedly have affected protein transport, enzyme activation, protein acylation, cell signaling, and transcriptional regulation. [1] The formation of fatty acyl-CoA is catalyzed in two steps: a stable intermediate of fatty acyl-AMP molecule and then the product is formed—fatty acid acyl-CoA molecule. [4]
Fatty acyl CoA synthetase catalyzes the activation of a long fatty acid chain to a fatty acyl CoA, requiring the energy of 1 ATP to AMP and pyrophosphate. This step uses 2 "ATP equivalents" because pyrophosphate is cleaved into 2 molecules of inorganic phosphate, breaking a high-energy phosphate bond.
The mechanism for Long Chain Fatty Acyl-CoA Synthetase is a “bi uni uni bi ping-pong” mechanism. [1] The uni and bi prefixes refer to the number of substrates that enter the enzyme and the number of products that leave the enzyme; bi describes a situation where two substrates enter the enzyme at the same time. Ping-pong signifies that a product is released before another substrate can bind to the enzyme.
In step one, ATP and a long chain fatty acid enter the enzyme's active site. Within the active site the negatively charged oxygen on the fatty acid attacks the alpha phosphate on ATP, forming an ATP-long chain fatty acid intermediate. (Step 1, Figure 2) In the second step, Pyrophosphate (PPi) leaves, resulting in an AMP-long chain fatty acid molecule within the enzyme's active site. (Step 2, Figure 2) Coenzyme A now enters the enzyme and another intermediate is formed which consists of AMP-long chain fatty acid-Coenzyme A. (Step 3, Figure 2) At the end of this mechanism two products are released, AMP and acyl coa product. (Step 4, Figure 2)
Acyl CoA is formed from long chain fatty acids through an acyl substitution. In an ATP dependent reaction, the fatty acid carboxylate is converted to a thioester. The final products of this reaction are acyl-CoA, pyrophosphate (PPi) and AMP.
There are several highly conserved areas and a 20-30% amino acid sequence similarity between the members of this superfamily. [1] The enzymes in the family consist of a large N-terminal and a small C-terminal domain, with the catalytic site positioned between the two domains. [1] Substrate binding may affect the relative positions of the C- and N-terminal domains. The C-terminal domain of LC-FACS is assumed to be in an open conformation when a substrate is absent and in a closed conformation when a substrate is bound. [1] The accessibility of the active site to solvent is reduced when the C- and N-terminal domains approach one another. [5]
The structure-function relationship between LC-FACS and the formation and processing of the acyl-AMP intermediate was still unclear. A domain swapped dimer is formed by LC-FACS, with monomer interacting at the N-terminal domains. [6] A large electrostatically positive concave is located at the back of the structure in the central valley of the homodimer. [1] Asp15 forms an intermolecular salt bridge with Arg176 in the dimer interactions. An intermolecular hydrogen bond is formed between the main chain carbonyl group of Glu16and the side chain of Arg199. At the interface, Glu175 forms an intermolecular salt bridge with Arg199. [5] [7] [8] [9] The L motif, a six-amino acid peptide linker, connects the large N-terminal domain and a small C-terminal domain of each LC-FACS monomer. [1] The N-terminal domain is composed of two subdomains: a distorted antiparallel β-barrel and two β-sheets surrounded by α-helices forming an αβαβα sandwich. [1] The small C-terminal globular domain consists of two-stranded β-sheet and a three-stranded antiparallel β-sheet flanked by three α-helices. [1]
The dimerization of LC-FACS is stabilized through a salt bridge between Asp15 of sequence A and Arg176 of sequence B. Figure 3 shows this salt bridge between these two amino acids. The yellow line between Asp15 and Arg176 shows the salt bridge present.
The conformations of the C-terminal domain of the LC-FACS structures are dependent on the presence of a ligand. [1] AMP-PNP, a nonhydrolyzable ATP analogue, bound to LC-FACS results in the closed conformation with the C- and N-terminal domains directly interacting. [1] In crystal structures, AMP-PNP is bound in a crevasse of each monomer at the interface between the N- and C-terminal domains. [1] The closed conformation of the C-terminal domain is retained with myristroyl-AMP. [1] Three residues in the C-terminal domain, Glu443, Glu475, and Lys527, interact noncovalently with L motif residues and the N-terminal domain to stabilize the closed conformation. [1] There are two types of open conformations in the C-terminal domains of the uncomplexed structure. The C- and N-terminal domains do not interact directly for both monomers of the dimer. [1] An extensive hydrogen bond network is used by the AMP moiety of the bound ATP molecule to hold the C- and N-terminal domains together. [1]
Bulkier long chain fatty acids are bound by a fatty acid-binding tunnel that is located in the N-terminal domain of each monomer. [1] A large β-sheet and an α-helix cluster surround the tunnel which extends from the concave cavity in the central valley to the site of ATP-binding. [1] There are two distinct paths in the large central pathway of the tunnel in the complex structure, which includes the “ATP path” and the “center path,” separated by the indole ring of Trp234 in the G motif. [1] There is also another branch of the central pathway known as the “dead and branch.” The indole ring of Trp234 closes the fatty acid-binding tunnel in the uncomplexed structure. [1] It opens up once AMP-PNP binds through hydrogen bond formation between β-phosphate and the nitrogen on the ring of Trp234. [1] During this time, the closed conformation is adopted by the mobile C-terminal domain. There is a shift in the flexible loop of the G motif in the closed structures of LC-FACS, resulting in a wider dead end branch compared to the uncomplexed forms. [1]
The ATP binding site is connected to an ATP path that is a hydrophobic channel in the fatty acid-binding tunnel. [1] The fatty acid enters through the center path extending from the interface of the dimer along β-strand 13 to the ATP path. [1] The connection between the two paths is blocked by the indole ring of Trp234 in the absence of ATP. Water molecules fill the center path in the AMP-PNP and myristoyl-AMP complex structures and through the entrance of the center path, they connect to the bulk solvent regions. The basic residues from each monomer, Lys219, Arg296, Arg297, Arg321, Lys350, and Lys 354, cause the entrance of the center path to generate a positive electrostatic potential. [1] The dead end branch contains residues 235-243 and extends from the fatty acid-binding tunnel to α-helix h. [1] The bottom of the dead end branch consists of a hydrophilic environment from the water molecules and polar side chains. [1]
The domains founds in Long chain fatty acyl CoA synthetase are shown both in the enzyme view (figure 5) and sequence view (figure 6). LC-FACS has five domains. After searching 1v26 in Entrez, the location of the 5 domains was shown and was used to create figure 5 and 6. The ribbons colors in figure 5 correspond to the colors of the figure 6.
A long term and short term regulation controls fatty acid synthesis. [4] Long term fatty acid synthesis regulation is dependent on the rate of acetyl-CoA carboxylase (ACC) synthesis, the rate-limiting enzyme and first enzyme of the fatty acid synthesis, and fatty acid synthase (FAS), the second and major enzyme of the fatty acid synthesis. [4] [10] [11] [12] Cellular fatty acyl-CoA is involved in the short term regulation, but there is not a full understanding of the mechanisms. [13]
Free fatty acids inhibits the de novo fatty acid synthesis and appears to be dependent on the formation of long chain fatty acyl-CoAs. [14] Studies have shown that long chain fatty acyl-CoAs inhibit ACC and FAS via feedback inhibition. [15] [16] [17] [18] Long chain fatty acyl-CoA's inhibitory effect on the fatty acid synthesis may be a result of its regulation of lipogenic enzymes in a feedback manner through gene transcription suppression. [19]
Long-chain fatty-acid-CoA ligase in cells catalytically synthesizes long chain fatty acyl-CoAs. Long-chain fatty-acid-CoA ligase may be involved in an important role in the suppression of fatty acid synthesis and it has been reported that it played a part in fatty acid synthesis inhibition. [20] It was recently found that vitamin D3 upregulates FACL3, which forms long-chain fatty acid synthesis through the use of myristic acid, eicosapentaenoic acid (EPA), and arachidonic acid as substrates, in expression and activity levels. [21] FACL3 contributes to vitamin D3 growth inhibitory effect in human prostate cancer LNCaP cells. [21] A current study reports that the feedback inhibition of FAS expression by long chain fatty acyl-CoAs causes the downregulation of FAS mRNA by vitamin D3. [4] [22]
Adrenoleukodystrophy (ALD) is the build up of long chain fatty acids in the brain and adrenal cortex, because of the decreased activity of long chain fatty acyl coa synthetase. [23] The oxidation of the long chain fatty acids normally occurs in the peroxisome where the long chain fatty acyl coa synthetase is found. Long chain fatty acids enter the peroxisome via a transporter protein, ALDP, which creates a gate in the membrane of the peroxisome. In ALD the gene for this peroximal membrane transporter, ALDP, is defective, preventing long chain fatty acids from entering the peroxisome. [24]
Human genes encoding long-chain-fatty-acid—CoA ligase enzymes (also known as acyl-CoA synthetase long-chain, or ACSL) include:
In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2, which are co-enzymes used in the electron transport chain. It is named as such because the beta carbon of the fatty acid undergoes oxidation to a carbonyl group. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes.
Firefly luciferase is the light-emitting enzyme responsible for the bioluminescence of fireflies and click beetles. The enzyme catalyses the oxidation of firefly luciferin, requiring oxygen and ATP. Because of the requirement of ATP, firefly luciferases have been used extensively in biotechnology.
Acyl-CoA dehydrogenases (ACADs) are a class of enzymes that function to catalyze the initial step in each cycle of fatty acid β-oxidation in the mitochondria of cells. Their action results in the introduction of a trans double-bond between C2 (α) and C3 (β) of the acyl-CoA thioester substrate. Flavin adenine dinucleotide (FAD) is a required co-factor in addition to the presence of an active site glutamate in order for the enzyme to function.
Acyl-CoA is a group of coenzymes that metabolize fatty acids. Acyl-CoA's are susceptible to beta oxidation, forming, ultimately, acetyl-CoA. The acetyl-CoA enters the citric acid cycle, eventually forming several equivalents of ATP. In this way, fats are converted to ATP, the universal biochemical energy carrier.
Fatty acid degradation is the process in which fatty acids are broken down into their metabolites, in the end generating acetyl-CoA, the entry molecule for the citric acid cycle, the main energy supply of living organisms, including bacteria and animals. It includes three major steps:
Palmitoyl-CoA is an acyl-CoA thioester. It is an "activated" form of palmitic acid and can be transported into the mitochondrial matrix by the carnitine shuttle system, and once inside can participate in beta-oxidation. Alternatively, palmitoyl-CoA is used as a substrate in the biosynthesis of sphingosine.
Acetyl-CoA synthetase (ACS) or Acetate—CoA ligase is an enzyme involved in metabolism of acetate. It is in the ligase class of enzymes, meaning that it catalyzes the formation of a new chemical bond between two large molecules.
Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are enzymes which convert two units of acetyl-CoA to acetoacetyl CoA in the mevalonate pathway.
Pantothenate kinase (EC 2.7.1.33, PanK; CoaA) is the first enzyme in the Coenzyme A (CoA) biosynthetic pathway. It phosphorylates pantothenate (vitamin B5) to form 4'-phosphopantothenate at the expense of a molecule of adenosine triphosphate (ATP). It is the rate-limiting step in the biosynthesis of CoA.
In enzymology, a 4-coumarate—CoA ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a 6-carboxyhexanoate—CoA ligase is an enzyme that catalyzes the chemical reaction
Butyrate—CoA ligase, also known as xenobiotic/medium-chain fatty acid-ligase (XM-ligase), is an enzyme that catalyzes the chemical reaction:
In enzymology, a long-chain-fatty-acid—[acyl-carrier-protein] ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a long-chain-fatty-acid—luciferin-component ligase is an enzyme that catalyzes the chemical reaction
Fatty-acyl-CoA Synthase, or more commonly known as yeast fatty acid synthase, is an enzyme complex responsible for fatty acid biosynthesis, and is of Type I Fatty Acid Synthesis (FAS). Yeast fatty acid synthase plays a pivotal role in fatty acid synthesis. It is a 2.6 MDa barrel shaped complex and is composed of two, unique multi-functional subunits: alpha and beta. Together, the alpha and beta units are arranged in an α6β6 structure. The catalytic activities of this enzyme complex involves a coordination system of enzymatic reactions between the alpha and beta subunits. The enzyme complex therefore consists of six functional centers for fatty acid synthesis.
Long-chain-fatty-acid—CoA ligase 1 is an enzyme that in humans is encoded by the ACSL1 gene.
Very long-chain acyl-CoA synthetase is an enzyme that in humans is encoded by the SLC27A2 gene.
Acyl-coenzyme A thioesterase 11 also known as StAR-related lipid transfer protein 14 (STARD14) is an enzyme that in humans is encoded by the ACOT11 gene. This gene encodes a protein with acyl-CoA thioesterase activity towards medium (C12) and long-chain (C18) fatty acyl-CoA substrates which relies on its StAR-related lipid transfer domain. Expression of a similar murine protein in brown adipose tissue is induced by cold exposure and repressed by warmth. Expression of the mouse protein has been associated with obesity, with higher expression found in obesity-resistant mice compared with obesity-prone mice. Alternative splicing results in two transcript variants encoding different isoforms.
Bile acyl-CoA synthetase is an enzyme that in humans is encoded by the SLC27A5 gene.
Acyl-CoA thioesterase 13 is a protein that in humans is encoded by the ACOT13 gene. This gene encodes a member of the thioesterase superfamily. In humans, the protein co-localizes with microtubules and is essential for sustained cell proliferation.