GO:0120520 free fatty acid 2-hydroxylase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0120520 describes the enzymatic activity that converts a free 1,2-saturated fatty acid into an (R)-2-hydroxy fatty acid using cytochrome b5 as an electron donor and molecular oxygen [1,2].
• The reaction is catalyzed by fatty acid 2-hydroxylase (FA2H), a cytochrome b5-domain-containing enzyme that introduces a hydroxyl group at the alpha carbon of free fatty acids [2,3].
• FA2H-dependent 2-hydroxylation is essential for the synthesis of 2-hydroxy sphingolipids, which are abundant in myelin and skin [2,3].
• Mutations in FA2H cause hereditary spastic paraplegia and related neurodegenerative disorders.
• FA2H expression is upregulated in some cancers and promotes cell migration, making it a potential therapeutic target [1,5,6].
• Studying GO:0120520 requires combining lipidomics, enzyme assays, and CRISPR-based genetic models to dissect its role in health and disease [4,7].
Description
Free fatty acid 2-hydroxylase activity (GO:0120520) is a molecular function that catalyzes the stereospecific hydroxylation of free fatty acids at the C2 position, producing (R)-2-hydroxy fatty acids [1,2]. This reaction is dependent on cytochrome b5 as an electron donor and molecular oxygen, and it is distinct from the hydroxylation of fatty acyl chains already incorporated into sphingolipids. The enzyme responsible for this activity in mammals is fatty acid 2-hydroxylase (FA2H), a membrane-bound protein containing a cytochrome b5 domain [2,3]. FA2H was initially identified through its role in the synthesis of 2-hydroxy ceramides and 2-hydroxy sphingomyelin, which are critical components of myelin and the epidermal permeability barrier [2,3]. The importance of this activity is underscored by the finding that mutations in FA2H cause hereditary spastic paraplegia, a neurodegenerative disorder characterized by progressive spasticity and weakness. Additionally, FA2H has been implicated in cancer cell migration and aggressiveness, suggesting that this enzymatic activity has broad physiological and pathological relevance [1,5,6]. Understanding GO:0120520 therefore provides insights into lipid metabolism, membrane biology, and disease mechanisms.
free fatty acid 2-hydroxylase activity At A Glance
| GO ID | GO:0120520 |
|---|---|
| GO term | free fatty acid 2-hydroxylase activity |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Catalyzes the 2-hydroxylation of free fatty acids using cytochrome b5 and oxygen |
| Substrate | 1,2-saturated free fatty acid |
| Product | (R)-2-hydroxy fatty acid |
| Cofactors | Cytochrome b5 (Fe(II)), molecular oxygen, protons |
| Enzyme | Fatty acid 2-hydroxylase (FA2H) |
What Is GO:0120520?
GO:0120520, free fatty acid 2-hydroxylase activity, is defined as the catalysis of the reaction: a 1,2-saturated fatty acid + 2 Fe(II)-[cytochrome b5] + 2 H+ + O2 = a (R)-2-hydroxy fatty acid + 2 Fe(III)-[cytochrome b5] + H2O. This definition emphasizes that the substrate is a free fatty acid, not a fatty acyl chain within a sphingolipid [1,2]. The enzyme uses cytochrome b5 as an electron donor and incorporates one oxygen atom into the fatty acid, generating a hydroxyl group at the C2 position with R stereochemistry.
Why Is free fatty acid 2-hydroxylase activity Important in Cell Biology?
GO:0120520 is important because it represents a key enzymatic step in the production of 2-hydroxy fatty acids, which are essential for the synthesis of 2-hydroxy sphingolipids such as 2-hydroxy ceramides and 2-hydroxy sphingomyelin [2,3]. These lipids are critical for the structure and function of myelin in the nervous system and for the permeability barrier of the skin [2,3]. Dysregulation of this activity has been linked to hereditary spastic paraplegia, a neurodegenerative disease, and to cancer progression, where FA2H expression promotes cell migration and aggressiveness [1,5,6,7]. Therefore, understanding the molecular mechanism and regulation of free fatty acid 2-hydroxylase activity is crucial for developing therapeutic strategies for these conditions.
• Essential for myelin integrity: FA2H-dependent 2-hydroxylation is required for the synthesis of 2-hydroxy galactosylceramide, a major lipid in myelin.
• Skin barrier function: 2-hydroxy ceramides are abundant in the epidermis and are necessary for the permeability barrier.
• Neurodegeneration: Mutations in FA2H cause hereditary spastic paraplegia, highlighting the importance of this activity in motor neuron function.
• Cancer progression: FA2H expression is upregulated in breast cancer cells and promotes migration, suggesting a role in metastasis [1,5,6].
• Drug response: Δ9-tetrahydrocannabinol upregulates FA2H via PPARα, linking this activity to cannabinoid signaling.
• Environmental toxicology: Perfluorooctanoic acid stimulates FA2H expression and breast cancer cell aggressiveness.
• Lipid biomarker: 2-hydroxylated sphingomyelin profiles are altered in patients with FA2H mutations, serving as diagnostic markers.
• Therapeutic target: Inhibiting FA2H activity could reduce cancer cell migration and invasion [1,6].
What Happens During free fatty acid 2-hydroxylase activity?
Substrate binding and activation
In simple terms: The enzyme grabs a free fatty acid and prepares it for modification.
The reaction begins with the binding of a 1,2-saturated free fatty acid to the active site of FA2H. The enzyme contains a cytochrome b5 domain that facilitates electron transfer from NADH or NADPH via cytochrome b5 reductase. This binding positions the fatty acid for hydroxylation at the C2 position.
Electron transfer and oxygen activation
In simple terms: Electrons are delivered to the enzyme to activate oxygen.
Two molecules of Fe(II)-cytochrome b5 donate electrons to the enzyme, reducing molecular oxygen to a reactive species. This activation allows the oxygen to insert into the fatty acid chain. The cytochrome b5 domain of FA2H is essential for this electron transfer, as mutations in this domain impair activity.
Hydroxylation and product release
In simple terms: The fatty acid gets a hydroxyl group added, and the product is released.
The activated oxygen atom is inserted at the C2 position of the fatty acid, forming an (R)-2-hydroxy fatty acid. The reaction consumes two protons and produces water. The product, (R)-2-hydroxy fatty acid, is then released and can be further metabolized into 2-hydroxy sphingolipids [2,3].
Incorporation into sphingolipids
In simple terms: The modified fatty acid becomes part of complex lipids.
The (R)-2-hydroxy fatty acid produced by FA2H is subsequently incorporated into ceramides and sphingomyelin, generating 2-hydroxy sphingolipids [2,3]. These lipids are enriched in myelin and skin, where they contribute to membrane stability and barrier function [2,3]. In patients with FA2H mutations, 2-hydroxylated sphingomyelin levels are reduced, confirming the role of this activity in sphingolipid synthesis.
Key Genes Involved in GO:0120520 free fatty acid 2-hydroxylase activity
The following genes and proteins are directly involved in free fatty acid 2-hydroxylase activity or its downstream pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| FA2H | Catalyzes 2-hydroxylation of free fatty acids | Mutations cause spastic paraplegia; upregulated in cancer [1,7] |
| CYB5A | Provides electrons to FA2H as cytochrome b5 | Essential cofactor for FA2H activity |
| CYB5R3 | Reduces cytochrome b5 to maintain electron supply | Supports FA2H-mediated hydroxylation |
| PPARA | Transcription factor that upregulates FA2H | Mediates THC-induced FA2H expression |
| PPARD | Inhibits PPARα, indirectly affecting FA2H | Modulates FA2H expression in cancer cells |
| ESR1 | Estrogen receptor, may influence FA2H expression | Linked to breast cancer subtypes |
| SPTLC1 | Serine palmitoyltransferase, first step in sphingolipid synthesis | Provides substrates for 2-hydroxy sphingolipids |
| SPTLC2 | Subunit of serine palmitoyltransferase | Required for sphingolipid backbone synthesis |
| CERS2 | Ceramide synthase, incorporates 2-hydroxy fatty acids | Produces 2-hydroxy ceramides |
| UGCG | Glucosylceramide synthase, uses 2-hydroxy ceramides | Synthesizes 2-hydroxy galactosylceramide in myelin |
| GALC | Galactosylceramidase, degrades galactosylceramide | Defects cause Krabbe disease, related to myelin lipids |
| MBP | Myelin basic protein, major myelin component | Interacts with 2-hydroxy sphingolipids |
| PLP1 | Proteolipid protein, myelin structural protein | Myelin integrity depends on 2-hydroxy lipids |
| ABCD1 | Peroxisomal transporter, involved in fatty acid metabolism | May affect substrate availability for FA2H |
| SCD | Stearoyl-CoA desaturase, produces unsaturated fatty acids | Alters substrate pool for 2-hydroxylation |
| ELOVL | Fatty acid elongases, generate long-chain fatty acids | Provide substrates for FA2H |
| ACSL | Acyl-CoA synthetases, activate fatty acids | May compete with free fatty acid pool |
| FAAH | Fatty acid amide hydrolase, releases free fatty acids | Can supply substrates for 2-hydroxylation |
How Is free fatty acid 2-hydroxylase activity Regulated?
FA2H expression is regulated at the transcriptional level by nuclear receptors such as PPARα, which is activated by Δ9-tetrahydrocannabinol and other ligands. In MDA-MB-231 breast cancer cells, PPARβ/δ inhibits PPARα, thereby suppressing FA2H expression, while THC cancels this inhibition and upregulates FA2H. Additionally, environmental factors such as perfluorooctanoic acid (PFOA) stimulate FA2H expression and promote cancer cell aggressiveness. Post-translational regulation may involve the cytochrome b5 domain, as mutations in this domain impair enzyme activity. The activity is also dependent on the availability of cytochrome b5 and its reductase, which supply electrons.
free fatty acid 2-hydroxylase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FA2H | Hereditary spastic paraplegia | Patient-derived fibroblasts or iPSC-derived neurons with FA2H mutations |
| FA2H | Breast cancer metastasis | MDA-MB-231 cells with FA2H knockout or overexpression [1,6] |
| FA2H | Skin barrier dysfunction | Keratinocyte differentiation models with FA2H knockdown |
| FA2H | Leukodystrophy | Mouse models with Fa2h deletion |
| FA2H | Cancer drug response | Xenograft models treated with PPARα agonists |
Hereditary spastic paraplegia
Mutations in FA2H, including an 18 bp deletion in the cytochrome b5 domain, cause hereditary spastic paraplegia, a neurodegenerative disorder characterized by progressive spasticity and weakness. These mutations impair free fatty acid 2-hydroxylase activity, leading to reduced levels of 2-hydroxy sphingolipids in the nervous system. This highlights the critical role of GO:0120520 in motor neuron function and myelin maintenance.
Breast cancer
FA2H is upregulated in breast cancer cells and promotes cell migration, suggesting a role in metastasis. In MDA-MB-231 cells, FA2H expression is stimulated by THC via PPARα and by PFOA, leading to increased aggressiveness [5,6]. Therefore, free fatty acid 2-hydroxylase activity may be a therapeutic target to inhibit cancer cell migration [1,6].
Skin disorders
FA2H accounts for the differentiation-associated increase in 2-hydroxy ceramides during keratinocyte differentiation, which are essential for the epidermal permeability barrier. Defects in this activity could contribute to skin barrier dysfunction, although direct evidence in human skin diseases is limited.
From free fatty acid 2-hydroxylase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does FA2H loss affect myelin lipid composition? | FA2H knockout mouse or rat |
| Can a point mutation in the cytochrome b5 domain abolish activity? | Knock-in of patient mutation in cell lines |
| Does FA2H overexpression increase 2-hydroxy sphingolipids? | FA2H overexpression in HEK293 or HeLa cells |
| What is the role of FA2H in cancer cell migration? | FA2H knockout in MDA-MB-231 cells |
| How does PPARα regulate FA2H transcription? | FA2H promoter reporter assays with PPARα agonists |
| Can tagged FA2H be used to study localization? | Knock-in of FLAG or GFP tag at endogenous locus |
How to Study the free fatty acid 2-hydroxylase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS lipidomics | Levels of 2-hydroxy fatty acids and sphingolipids | Quantifying FA2H activity in cells and tissues [2,4] |
| In vitro enzyme assay | Conversion of free fatty acids to 2-hydroxy products | Kinetic analysis and inhibitor screening |
| CRISPR knockout | Loss of FA2H function | Studying effects on migration and lipid composition |
| CRISPR knock-in | Introduction of patient mutations | Modeling hereditary spastic paraplegia |
| Luciferase reporter | FA2H promoter activity | Identifying transcriptional regulators |
| Immunoblotting | FA2H protein expression | Validating knockout or overexpression |
| Immunofluorescence | Subcellular localization of FA2H | Determining organelle distribution |
| Migration assay | Cell motility | Assessing cancer aggressiveness [1,6] |
Lipidomics and mass spectrometry
Mass spectrometry-based lipidomics is used to quantify 2-hydroxy fatty acids and 2-hydroxy sphingolipids in cells and tissues [2,4]. This method can detect changes in FA2H activity by measuring the ratio of 2-hydroxylated to non-hydroxylated species. It is particularly useful for analyzing patient samples with FA2H mutations.
Enzyme activity assays
In vitro enzyme assays using recombinant FA2H and cytochrome b5 can directly measure the conversion of free fatty acids to 2-hydroxy fatty acids. These assays typically use radiolabeled or fluorescent substrates and require NADH or NADPH as electron donors. They are essential for determining kinetic parameters and testing inhibitors.
CRISPR-Cas9 knockout and knock-in
CRISPR-Cas9 genome editing is used to generate FA2H knockout cell lines to study loss of function. Knock-in of specific patient mutations, such as the 18 bp deletion, allows investigation of disease mechanisms. These models are valuable for validating drug targets and understanding FA2H biology [1,7].
Transcriptional reporter assays
Luciferase reporter assays driven by the FA2H promoter are used to study transcriptional regulation by PPARα and other factors. These assays can be combined with CRISPR interference or activation to modulate transcription. They help identify upstream regulators of free fatty acid 2-hydroxylase activity.
How CRISPR Can Be Used to Study GO:0120520 free fatty acid 2-hydroxylase activity
Knockout
CRISPR-Cas9 knockout of FA2H is used to completely abolish free fatty acid 2-hydroxylase activity, allowing researchers to study its role in lipid metabolism and cell behavior. For example, FA2H knockout in MDA-MB-231 cells reduces cell migration, demonstrating its role in cancer aggressiveness. Knockout models are also valuable for validating the specificity of enzyme inhibitors.
Point Mutation
Point mutations in the cytochrome b5 domain of FA2H, such as those found in hereditary spastic paraplegia patients, can be introduced using CRISPR-Cas9 homology-directed repair. These models help dissect the molecular consequences of specific mutations on enzyme activity and protein stability. They are essential for understanding genotype-phenotype correlations.
Knock-in
Knock-in of tags such as FLAG or GFP at the endogenous FA2H locus enables real-time tracking of enzyme localization and interaction partners. Knock-in of patient-specific mutations, like the 18 bp deletion, creates isogenic models for drug testing. These models preserve endogenous regulatory elements, providing more physiological relevance.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of FA2H is used to increase free fatty acid 2-hydroxylase activity, leading to elevated 2-hydroxy sphingolipid levels. Overexpression models are useful for studying downstream effects on membrane properties and cell signaling. They can also be used to screen for compounds that modulate the enzyme's activity.
How EDITGENE Supports free fatty acid 2-hydroxylase activity Research
Researchers studying free fatty acid 2-hydroxylase activity-related genes often need to determine whether a candidate gene is causally involved in lipid metabolism, cancer progression, or neurodegeneration. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional studies of GO:0120520 and its associated pathways.
Contact EDITGENE today to design your custom CRISPR model for free fatty acid 2-hydroxylase activity research.
Frequently Asked Questions About free fatty acid 2-hydroxylase activity
What is free fatty acid 2-hydroxylase activity?
It is the enzymatic activity (GO:0120520) that catalyzes the addition of a hydroxyl group to the C2 position of free fatty acids, producing (R)-2-hydroxy fatty acids, using cytochrome b5 and oxygen [1,2].
What genes are involved in free fatty acid 2-hydroxylase activity?
The primary gene is FA2H, which encodes fatty acid 2-hydroxylase. Other supporting genes include CYB5A and CYB5R3 for electron transfer, and PPARA for transcriptional regulation [2,5].
What diseases are associated with FA2H mutations?
FA2H mutations cause hereditary spastic paraplegia, a neurodegenerative disorder. FA2H is also implicated in breast cancer progression and skin barrier defects [1,3,7].
How is free fatty acid 2-hydroxylase activity measured?
It is measured using mass spectrometry-based lipidomics to quantify 2-hydroxy fatty acids and sphingolipids, or in vitro enzyme assays with recombinant FA2H and cytochrome b5 [2,4].
What is the role of FA2H in cancer?
FA2H promotes cancer cell migration and aggressiveness, particularly in breast cancer. Its expression is upregulated by factors like THC and PFOA [1,5,6].
Can CRISPR be used to study FA2H function?
Yes, CRISPR-Cas9 knockout, knock-in, and overexpression models are widely used to study FA2H function in lipid metabolism and disease [1,7].
What are 2-hydroxy sphingolipids?
They are sphingolipids containing 2-hydroxy fatty acids, synthesized from FA2H products. They are abundant in myelin and skin and are essential for membrane function [2,3].
How is FA2H expression regulated?
FA2H is transcriptionally regulated by PPARα, which is activated by ligands such as THC. PPARβ/δ can inhibit PPARα, reducing FA2H expression.
What is the difference between free fatty acid 2-hydroxylase and sphingolipid 2-hydroxylase?
Free fatty acid 2-hydroxylase acts on free fatty acids, not on fatty acyl chains already incorporated into sphingolipids, as specified in the GO definition [1,2].
Are there animal models for FA2H deficiency?
Yes, Fa2h knockout mice have been generated and show alterations in myelin lipids, modeling aspects of hereditary spastic paraplegia.
Conclusion
Free fatty acid 2-hydroxylase activity (GO:0120520) is a critical enzymatic function in lipid metabolism, responsible for the synthesis of 2-hydroxy fatty acids and downstream 2-hydroxy sphingolipids. Its importance is highlighted by its role in myelin maintenance, skin barrier formation, and cancer progression [1,2,3,7]. Understanding the molecular mechanism and regulation of this activity provides opportunities for therapeutic intervention in neurodegenerative diseases and cancer. EDITGENE offers comprehensive CRISPR services to facilitate research on FA2H and related pathways, enabling the development of novel treatments.
References
- 1. Hirao-Suzuki M et al.. 2020. Fatty acid 2-hydroxylase (FA2H) as a stimulatory molecule responsible for breast cancer cell migration.. Biochem Biophys Res Commun 531(2):215-222 PMID: 32798015
- 2. Alderson NL et al.. 2006. FA2H-dependent fatty acid 2-hydroxylation in postnatal mouse brain.. J Lipid Res 47(12):2772-80 PMID: 16998236
- 3. Uchida Y et al.. 2007. Fatty acid 2-hydroxylase, encoded by FA2H, accounts for differentiation-associated increase in 2-OH ceramides during keratinocyte differentiation.. J Biol Chem 282(18):13211-9 PMID: 17355976
- 4. Dan P et al.. 2011. 2-Hydroxylated sphingomyelin profiles in cells from patients with mutated fatty acid 2-hydroxylase.. Lipids Health Dis 10:84 PMID: 21599921
- 5. Hirao-Suzuki M et al.. 2019. Δ(9)-Tetrahydrocannabinol upregulates fatty acid 2-hydroxylase (FA2H) via PPARα induction: A possible evidence for the cancellation of PPARβ/δ-mediated inhibition of PPARα in MDA-MB-231 cells.. Arch Biochem Biophys 662:219-225 PMID: 30553767
- 6. Sakai G et al.. 2022. Perfluorooctanoic acid (PFOA) as a stimulator of estrogen receptor-negative breast cancer MDA-MB-231 cell aggressiveness: Evidence for involvement of fatty acid 2-hydroxylase (FA2H) in the stimulated cell migration.. J Toxicol Sci 47(4):159-168 PMID: 35370244
- 7. Abbas S et al.. 2021. Exome sequencing of a Pakistani family with spastic paraplegia identified an 18 bp deletion in the cytochrome B5 domain of FA2H.. Neurol Res 43(2):133-140 PMID: 33246395
