GO:0015645 fatty acid ligase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0015645 (fatty acid ligase activity) catalyzes ATP-dependent ligation of a fatty acid to an acceptor, typically coenzyme A, forming fatty acyl-CoA.
• The reaction proceeds through a two-step mechanism involving fatty acyl-AMP and pyrophosphate release, and is essential for fatty acid activation prior to beta-oxidation or lipid synthesis.
• The acyl-CoA synthetase long-chain (ACSL) family (ACSL1, ACSL3, ACSL4, ACSL5, ACSL6) are the principal enzymes carrying this activity in mammals.
• ACSL1 is regulated by TANK-binding kinase 1 (TBK1), which controls its localization to mitochondria and thus hepatic fatty acid oxidation.
• ACSL4 drives ferroptosis and promotes triple-negative breast cancer metastasis via H3K9/H3K27 hyperacetylation and SNAIL upregulation.
• Dysregulated fatty acid ligase activity is implicated in hepatic steatosis, insulin resistance, NASH, thermogenic adipose dysfunction, and cancer.
Description
Fatty acid ligase activity (GO:0015645) is a fundamental enzymatic function that activates fatty acids by conjugating them to coenzyme A (CoA) in an ATP-dependent manner, producing fatty acyl-CoA. This activation step is obligatory for nearly all downstream fatty acid metabolism, including beta-oxidation, glycerolipid synthesis, and protein acylation. The reaction is catalyzed by a family of enzymes known as acyl-CoA synthetases (ACS), which are classified by fatty acid chain length specificity. In mammals, the long-chain acyl-CoA synthetase (ACSL) family comprises five isoforms (ACSL1, ACSL3, ACSL4, ACSL5, and ACSL6) that activate fatty acids of 12-20 carbons. The importance of this activity extends beyond basic metabolism; recent studies have shown that ACSL1 localization and activity are regulated by TBK1 to control hepatic fatty acid oxidation, and that ACSL4-mediated histone acetylation drives cancer metastasis. Consequently, understanding GO:0015645 is critical for researchers studying metabolic diseases, cancer, and thermogenesis.
fatty acid ligase activity At A Glance
| GO ID | GO:0015645 |
|---|---|
| GO term | fatty acid ligase activity |
| Ontology | molecular_function |
| Synonym | fatty acid CoA ligase activity; fatty-acid ligase activity; fatty acyl-coenzyme A synthetase activity |
| Definition | Catalysis of the ligation of a fatty acid to an acceptor, coupled to the hydrolysis of ATP. |
| Major function | ATP-dependent activation of fatty acids to fatty acyl-CoA for beta-oxidation, lipid synthesis, and signaling. |
| Representative enzymes | ACSL1, ACSL3, ACSL4, ACSL5, ACSL6 (long-chain); other ACS family members for different chain lengths. |
| Cofactors | ATP, Mg2+, coenzyme A (acceptor). |
| Reaction products | Fatty acyl-CoA, AMP, pyrophosphate (PPi). |
What Is GO:0015645?
According to the Gene Ontology, fatty acid ligase activity (GO:0015645) is defined as the catalysis of the ligation of a fatty acid to an acceptor, coupled to the hydrolysis of ATP. This activity is synonymous with fatty acid CoA ligase activity, fatty-acid ligase activity, and fatty acyl-coenzyme A synthetase activity. In practice, the acceptor is usually coenzyme A, and the reaction forms a thioester bond between the fatty acid carboxyl group and the thiol group of CoA, yielding fatty acyl-CoA, AMP, and pyrophosphate.
Why Is fatty acid ligase activity Important in Cell Biology?
Fatty acid ligase activity is a metabolic gatekeeper: without it, fatty acids cannot be oxidized for energy or incorporated into complex lipids. This activity is essential for normal physiology, including hepatic fatty acid oxidation, thermogenesis in brown adipose tissue, and membrane biogenesis. Its dysregulation contributes to prevalent human diseases such as nonalcoholic steatohepatitis (NASH), insulin resistance, and cancer progression. Therefore, targeting this activity or its regulatory enzymes offers therapeutic potential, and understanding its mechanism is a prerequisite for rational drug design.
• Required for beta-oxidation of fatty acids in mitochondria and peroxisomes.
• Essential for synthesis of triglycerides, phospholipids, and cholesteryl esters.
• Regulates hepatic fatty acid oxidation via TBK1-mediated ACSL1 localization.
• Drives thermogenic adipose tissue function by providing acyl-CoA for uncoupled respiration.
• ACSL4 promotes ferroptosis and cancer metastasis through histone acetylation.
• ACSL4 inhibition ameliorates NASH in preclinical models.
• Ergosterol enhances mitochondrial ACSL1 activity to alleviate steatosis and insulin resistance.
• ACSL family members are emerging therapeutic targets in oncology.
• Fatty acid transport proteins (FATPs) may also possess ligase activity, linking transport to activation.
• Mutations or altered expression of ACS enzymes are associated with metabolic disorders.
What Happens During fatty acid ligase activity?
Substrate binding and adenylation
In simple terms: The enzyme first grabs a fatty acid and ATP, then attaches AMP to the fatty acid, releasing pyrophosphate.
The catalytic cycle begins with the binding of a fatty acid and ATP to the enzyme. In a reaction that requires Mg2+, the enzyme catalyzes the adenylation of the fatty acid carboxylate, forming a fatty acyl-AMP intermediate and releasing pyrophosphate (PPi). This step is analogous to the activation of amino acids in protein synthesis and is highly conserved among acyl-CoA synthetases.
Thioester formation with coenzyme A
In simple terms: The activated fatty acid is then handed over to coenzyme A, forming fatty acyl-CoA.
In the second step, the fatty acyl-AMP intermediate reacts with the thiol group of coenzyme A, displacing AMP and forming a thioester bond between the fatty acid and CoA. The products are fatty acyl-CoA and AMP. This thioesterification is energetically favorable and traps the fatty acid in an activated form suitable for further metabolism.
Chain-length specificity and enzyme families
In simple terms: Different enzymes prefer fatty acids of different lengths, so the cell uses a family of ligases.
Mammalian acyl-CoA synthetases are classified by their preferred fatty acid chain length: short-chain (ACSS), medium-chain (ACSM), long-chain (ACSL), and very long-chain (ACSVL/FATP). The ACSL family members (ACSL1, 3, 4, 5, 6) activate fatty acids of 12-20 carbons and are the most studied in the context of GO:0015645. Each isoform exhibits distinct tissue distribution and subcellular localization, allowing fine-tuned regulation of fatty acid flux.
Subcellular localization and metabolic channeling
In simple terms: Where the enzyme sits in the cell determines what happens to the activated fat.
ACSL1 is localized to mitochondria-associated membranes and lipid droplets, where it channels fatty acyl-CoA toward beta-oxidation or esterification. TBK1 regulates the localization of ACSL1 to mitochondria, thereby controlling hepatic fatty acid oxidation. Similarly, ACSL4 is enriched in peroxisomes and endoplasmic reticulum, and its activity influences ferroptosis and lipid signaling. This spatial organization ensures that the products of GO:0015645 are directed to appropriate metabolic pathways.
Key Genes Involved in GO:0015645 fatty acid ligase activity
The following genes encode enzymes that directly carry fatty acid ligase activity (GO:0015645) or are critical regulators of this activity in mammals.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ACSL1 | Long-chain acyl-CoA synthetase; activates C12-C20 fatty acids, channels them to beta-oxidation or esterification. | Hepatic fatty acid oxidation, insulin resistance, steatosis; regulated by TBK1. |
| ACSL3 | Long-chain acyl-CoA synthetase; associated with lipid droplets and phospholipid synthesis. | Lipid metabolism, cancer cell proliferation. |
| ACSL4 | Long-chain acyl-CoA synthetase; activates arachidonic acid and other PUFAs; involved in ferroptosis. | NASH, triple-negative breast cancer metastasis, ferroptosis. |
| ACSL5 | Long-chain acyl-CoA synthetase; localized to endoplasmic reticulum and mitochondria. | Lipid homeostasis, insulin sensitivity. |
| ACSL6 | Long-chain acyl-CoA synthetase; highly expressed in brain and testis. | Neuronal lipid metabolism, spermatogenesis. |
| ACSS1 | Acetyl-CoA synthetase 1; activates acetate to acetyl-CoA in mitochondria. | Energy metabolism, ketone body utilization. |
| ACSS2 | Acetyl-CoA synthetase 2; activates acetate to acetyl-CoA in cytosol/nucleus. | Cancer metabolism, histone acetylation. |
| ACSM1 | Medium-chain acyl-CoA synthetase; activates C4-C12 fatty acids. | Fatty acid oxidation disorders. |
| ACSM3 | Medium-chain acyl-CoA synthetase; may regulate lipid and glucose metabolism. | Metabolic syndrome. |
| SLC27A1 (FATP1) | Very long-chain acyl-CoA synthetase; also transports fatty acids. | Fatty acid uptake and activation in adipose and muscle. |
| SLC27A2 (FATP2) | Very long-chain acyl-CoA synthetase; peroxisomal and ER localization. | Lipid metabolism, drug metabolism. |
| SLC27A4 (FATP4) | Very long-chain acyl-CoA synthetase; major FATP in intestine. | Dietary fat absorption. |
| TBK1 | Serine/threonine kinase; regulates ACSL1 localization to mitochondria. | Hepatic fatty acid oxidation, inflammation. |
| SNAIL | Transcription factor; upregulated by ACSL4-mediated histone acetylation. | Epithelial-mesenchymal transition, cancer metastasis. |
| PPARalpha | Nuclear receptor; transcriptional regulator of fatty acid oxidation genes including ACSL1. | Fasting response, lipid homeostasis. |
| SREBP1c | Transcription factor; regulates lipogenic genes including ACSL1. | Lipogenesis, insulin resistance. |
| AMPK | Energy sensor kinase; phosphorylates and inhibits ACC, indirectly affecting fatty acid ligase demand. | Metabolic stress, energy homeostasis. |
How Is fatty acid ligase activity Regulated?
Fatty acid ligase activity is regulated at multiple levels. Transcriptionally, ACSL1 is induced by PPARalpha during fasting and by SREBP1c under lipogenic conditions. Post-translationally, TBK1 phosphorylates and controls the localization of ACSL1 to mitochondria, thereby modulating hepatic fatty acid oxidation. ACSL4 activity can be influenced by its expression level, which is elevated in aggressive cancers and contributes to histone acetylation and metastasis. Additionally, the availability of substrates (fatty acids, CoA, ATP) and the cellular energy status (AMP/ATP ratio) indirectly regulate flux through this activity. In thermogenic adipose tissue, fatty acid activation is tightly coupled to uncoupling protein 1 (UCP1) activity to support heat production.
fatty acid ligase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ACSL1 | Hepatic steatosis, insulin resistance | Liver-specific knockout or overexpression in mice |
| ACSL4 | NASH, triple-negative breast cancer metastasis | ACSL4 knockout or pharmacological inhibition in cell lines and mouse models |
| ACSL5 | Lipid homeostasis, insulin sensitivity | Tissue-specific knockout in mice |
| SLC27A1 (FATP1) | Obesity, fatty acid uptake | Transgenic overexpression or knockout in adipose tissue |
| ACSS2 | Cancer metabolism, histone acetylation | Knockdown or knockout in cancer cell lines |
Metabolic liver disease and insulin resistance
Dysregulated fatty acid ligase activity contributes to hepatic steatosis and insulin resistance. ACSL1 activation by ergosterol promotes mitochondrial beta-oxidation and alleviates steatosis in mice. Conversely, TBK1-mediated regulation of ACSL1 localization is critical for maintaining hepatic fatty acid oxidation, and its disruption may exacerbate lipid accumulation. ACSL4 targeting ameliorates NASH in preclinical models, highlighting the therapeutic potential of modulating this activity.
Cancer progression and metastasis
ACSL4-mediated activation of long-chain polyunsaturated fatty acids supports cancer cell proliferation and metastasis. In triple-negative breast cancer, ACSL4 promotes H3K9 and H3K27 hyperacetylation, leading to upregulation of SNAIL and enhanced metastatic capacity. The ACSL family is increasingly recognized as a therapeutic target in oncology, with isoform-specific roles in lipid signaling and energy metabolism.
Thermogenesis and adipose tissue dysfunction
In brown and beige adipose tissue, fatty acid ligase activity is essential for providing acyl-CoA substrates for thermogenesis. Impaired fatty acid activation in thermogenic adipose tissue is associated with obesity and cold intolerance. The interplay between fatty acid transport proteins (FATPs) and ACSL enzymes ensures efficient substrate channeling for heat production.
From fatty acid ligase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ACSL1 affect hepatic fatty acid oxidation? | Liver-specific ACSL1 knockout mouse |
| Can ACSL4 inhibition ameliorate NASH? | ACSL4 knockout or antisense oligonucleotide in diet-induced NASH mice |
| Does ACSL4-mediated histone acetylation drive metastasis? | ACSL4 knockout in triple-negative breast cancer cell lines and xenografts |
| Is TBK1 required for ACSL1 mitochondrial localization? | TBK1 knockout or kinase-dead knock-in cells |
| Does ergosterol enhance ACSL1 activity? | ACSL1 overexpression or activation in hepatocytes |
| What is the role of FATP1 in fatty acid activation? | FATP1 knockout or overexpression in adipocytes |
How to Study the fatty acid ligase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled fatty acid assay | Enzymatic formation of acyl-CoA | Kinetic analysis of ACSL isoforms |
| Coupled spectrophotometric assay | AMP production or CoA consumption | High-throughput inhibitor screening |
| Subcellular fractionation + immunoblot | Protein localization | ACSL1 mitochondrial targeting |
| Fluorescence microscopy | Live-cell localization of tagged ACSL | TBK1-dependent trafficking |
| RNA-seq | Gene expression levels | ACSL family expression profiling |
| Phosphoproteomics | Post-translational modifications | TBK1-mediated ACSL1 phosphorylation |
| Lipidomics | Acyl-CoA and lipid species | Metabolic flux analysis |
| CRISPR knockout screens | Gene essentiality and pathway dependencies | Cancer cell line fitness |
Enzymatic activity assays
Fatty acid ligase activity can be measured using radiolabeled fatty acids (e.g., 14C-oleate) and thin-layer chromatography to detect acyl-CoA formation, or by coupled spectrophotometric assays that monitor AMP production. These assays are used to determine kinetic parameters and isoform specificity.
Subcellular fractionation and imaging
To study localization, subcellular fractionation followed by immunoblotting for ACSL1 or ACSL4 can separate mitochondria, ER, and lipid droplets. Fluorescence microscopy with tagged proteins (e.g., GFP-ACSL1) allows live-cell tracking of localization changes in response to TBK1 signaling.
Transcriptomics and proteomics
RNA-seq can quantify ACSL family expression across tissues or disease states. Proteomics, including phosphoproteomics, can identify post-translational modifications such as TBK1-mediated phosphorylation of ACSL1. Lipidomics complements these by measuring acyl-CoA species and complex lipids.
Genetic perturbation and CRISPR screens
CRISPR knockout of ACSL genes in cell lines or organoids enables loss-of-function studies to assess effects on fatty acid oxidation, lipid accumulation, or ferroptosis. Overexpression or point-mutation knock-in models can dissect catalytic residues or regulatory phosphorylation sites.
How CRISPR Can Be Used to Study GO:0015645 fatty acid ligase activity
Knockout
CRISPR-Cas9 knockout of ACSL genes (e.g., ACSL1, ACSL4) in cell lines or primary cells is used to abolish fatty acid ligase activity and assess downstream effects on beta-oxidation, lipid storage, and ferroptosis. Liver-specific knockout in mice can model NASH and insulin resistance.
Point Mutation
Point mutations can be introduced into catalytic residues of ACSL enzymes (e.g., the AMP-binding motif) to dissect the enzymatic mechanism of GO:0015645. Similarly, phosphorylation site mutants of ACSL1 can test the role of TBK1-mediated regulation.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins at the endogenous ACSL1 locus allows for localization and interaction studies under native expression levels. Knock-in of disease-associated variants can model human metabolic disorders.
Overexpression
Overexpression of ACSL isoforms in cell lines or transgenic mice can enhance fatty acid ligase activity, leading to increased acyl-CoA pools and altered lipid metabolism. This approach is useful for studying gain-of-function effects in steatosis and thermogenesis.
How EDITGENE Supports fatty acid ligase activity Research
Researchers studying fatty acid ligase activity-related genes often need to determine whether a candidate gene is causally involved in metabolic or oncogenic phenotypes. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell and animal models, enabling rigorous functional validation of genes encoding or regulating GO:0015645.
Contact EDITGENE today to design your custom CRISPR model for fatty acid ligase activity research.
Frequently Asked Questions About fatty acid ligase activity
What is fatty acid ligase activity?
Fatty acid ligase activity (GO:0015645) is the ATP-dependent catalysis of ligating a fatty acid to an acceptor, typically coenzyme A, forming fatty acyl-CoA.
What genes are involved in fatty acid ligase activity?
The main genes are ACSL1, ACSL3, ACSL4, ACSL5, ACSL6, as well as ACSS1/2, ACSM1/3, and SLC27A (FATP) family members.
What is the GO ID for fatty acid ligase activity?
The Gene Ontology ID is GO:0015645, under the molecular_function aspect.
How is fatty acid ligase activity regulated?
It is regulated transcriptionally by PPARalpha and SREBP1c, and post-translationally by TBK1-mediated phosphorylation of ACSL1.
Which diseases are linked to fatty acid ligase activity?
Dysregulation is linked to NASH, insulin resistance, hepatic steatosis, obesity, and cancer metastasis.
What is the role of ACSL4 in cancer?
ACSL4 promotes H3K9/H3K27 hyperacetylation, upregulates SNAIL, and drives triple-negative breast cancer metastasis.
How can I study fatty acid ligase activity in the lab?
Common methods include radiolabeled fatty acid assays, subcellular fractionation, RNA-seq, lipidomics, and CRISPR knockout models.
What is the difference between ACSL and FATP?
ACSL enzymes are primarily ligases, while FATP (SLC27A) proteins can both transport fatty acids and possess ligase activity.
Can fatty acid ligase activity be targeted therapeutically?
Yes, ACSL4 inhibition ameliorates NASH in mice, and ACSL family members are considered promising cancer targets.
What CRISPR models are available for ACSL genes?
Knockout, point mutation, knock-in, and overexpression models can be generated in cell lines and mice to study ACSL function.
Conclusion
Fatty acid ligase activity (GO:0015645) is a central enzymatic function that activates fatty acids for diverse metabolic pathways. Its dysregulation is implicated in major human diseases, including NASH, insulin resistance, and cancer. The ACSL family and its regulators, such as TBK1, represent attractive targets for therapeutic intervention. Continued research using advanced CRISPR models and multi-omics approaches will further elucidate the mechanistic roles of this activity and facilitate the development of targeted therapies.
References
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- 2. Quan J et al.. 2021. ACSL family: The regulatory mechanisms and therapeutic implications in cancer.. Eur J Pharmacol 909:174397 PMID: 34332918
- 3. Zheng ZG et al.. 2025. Ergosterol alleviates hepatic steatosis and insulin resistance via promoting fatty acid β-oxidation by activating mitochondrial ACSL1.. Cell Rep 44(1):115203 PMID: 39799570
- 4. Duan J et al.. 2022. Therapeutic targeting of hepatic ACSL4 ameliorates NASH in mice.. Hepatology 75(1):140-153 PMID: 34510514
- 5. Gimeno RE. 2007. Fatty acid transport proteins.. Curr Opin Lipidol 18(3):271-6 PMID: 17495600
- 6. Sinha A et al.. 2024. ACSL4-mediated H3K9 and H3K27 hyperacetylation upregulates SNAIL to drive TNBC metastasis.. Proc Natl Acad Sci U S A 121(52):e2408049121 PMID: 39700137
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