GO:0140981 medium-chain fatty acid omega-hydroxylase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140981 describes the enzymatic activity that adds a hydroxyl group to the terminal (omega) carbon of medium-chain fatty acids (6-12 carbons), using O2 and NADPH-derived reducing equivalents.
• This activity is primarily carried out by cytochrome P450 enzymes of the CYP4 family, such as CYP4A11 in humans, which catalyzes lauric acid omega-hydroxylation.
• Medium-chain fatty acid omega-hydroxylase activity is involved in fatty acid catabolism and detoxification, and its dysregulation is linked to fatty liver disease and alcoholic liver injury [1,2].
• The reaction requires a redox partner, NADPH--hemoprotein reductase, to transfer electrons from NADPH to the P450 enzyme.
• Studying this activity helps researchers understand lipid metabolism, lipotoxicity, and potential therapeutic targets for metabolic disorders [1,5].
• CRISPR-based models (knockout, knock-in, overexpression) enable precise interrogation of genes encoding omega-hydroxylases and their regulators [7,8].
Description
Medium-chain fatty acid omega-hydroxylase activity (GO:0140981) is a molecular function that catalyzes the hydroxylation of the terminal methyl group of medium-chain fatty acids, converting them to omega-hydroxy fatty acids. This reaction is part of the broader fatty acid omega-oxidation pathway, which serves as an alternative route for fatty acid metabolism when beta-oxidation is impaired. The activity is essential for maintaining lipid homeostasis and preventing the accumulation of toxic fatty acid intermediates. In humans, cytochrome P450 enzymes, particularly those of the CYP4 family, are the main catalysts of this reaction. For example, CYP4A11 is the major lauric acid omega-hydroxylase in human liver microsomes, and its activity is regulated by peroxisome proliferator-activated receptors (PPARs) and retinoid X receptors (RXRs) [1,3]. The importance of this activity extends to disease contexts: alterations in fatty acid omega-hydroxylation have been observed in experimental alcoholic liver disease and in kidney disorders associated with nephrotic syndrome [2,5]. Moreover, microbial enzymes such as AlkBGT from Pseudomonas putida can perform similar omega-oxyfunctionalization of medium-chain fatty acids, highlighting the evolutionary conservation of this chemistry. Understanding GO:0140981 is therefore relevant for researchers in lipid biochemistry, hepatology, and metabolic engineering.
medium-chain fatty acid omega-hydroxylase activity At A Glance
| GO ID | GO:0140981 |
|---|---|
| GO term | medium-chain fatty acid omega-hydroxylase activity |
| Ontology | molecular_function |
| Synonym | None |
| Major function | Catalyzes omega-hydroxylation of medium-chain fatty acids (6-12 carbons) |
| Reaction | omega-methyl-medium-chain fatty acid + O2 + reduced [NADPH--hemoprotein reductase] = omega-hydroxy-medium-chain fatty acid + H+ + H2O + oxidized [NADPH--hemoprotein reductase] |
| Cofactors | O2, NADPH--hemoprotein reductase |
| Substrate specificity | Medium-chain fatty acids with 6-12 carbons |
| Major enzyme families | Cytochrome P450 (CYP4A, CYP4B, etc.) |
What Is GO:0140981?
GO:0140981, medium-chain fatty acid omega-hydroxylase activity, is defined as the catalysis of the reaction: an omega-methyl-medium-chain fatty acid + O2 + reduced [NADPH--hemoprotein reductase] = an omega-hydroxy-medium-chain fatty acid + H+ + H2O + oxidized [NADPH--hemoprotein reductase]. A medium-chain fatty acid has an aliphatic tail containing 6 to 12 carbons. In simpler terms, this activity adds a hydroxyl group to the last carbon (omega position) of a medium-chain fatty acid, using oxygen and electrons from NADPH via a reductase partner.
Why Is medium-chain fatty acid omega-hydroxylase activity Important in Cell Biology?
Medium-chain fatty acid omega-hydroxylase activity is critical for lipid metabolism and detoxification, as it provides an alternative pathway for fatty acid oxidation when beta-oxidation is compromised. This activity helps prevent lipotoxicity by converting medium-chain fatty acids into more water-soluble omega-hydroxy fatty acids that can be further metabolized or excreted. Dysregulation of this activity has been implicated in fatty liver disease, alcoholic liver injury, and kidney disorders, making it a potential therapeutic target [1,2,5]. Additionally, the ability to engineer this activity in microbial systems offers opportunities for biotechnological production of hydroxy fatty acids and biofuels [7,8].
• Provides an alternative route for fatty acid catabolism when beta-oxidation is impaired.
• Prevents lipotoxicity by converting medium-chain fatty acids to less toxic omega-hydroxy derivatives.
• Regulated by PPAR/RXR, linking it to energy homeostasis and lipid signaling.
• Altered in experimental alcoholic liver disease, suggesting a role in alcohol-induced liver injury.
• Dysregulated in kidney disorders such as PAN-induced nephrotic syndrome.
• CYP4A11 is the major lauric acid omega-hydroxylase in human liver, highlighting its importance in human metabolism.
• Microbial enzymes like AlkBGT enable omega-oxyfunctionalization for industrial applications.
• Potential target for treating fatty liver disease and related metabolic disorders.
• Useful for metabolic engineering of hydrocarbons and alkyl esters [7,8].
• Serves as a model for studying P450 enzyme mechanisms and substrate specificity.
Molecular Mechanism of medium-chain fatty acid omega-hydroxylase activity
Substrate Binding and Activation
In simple terms: The enzyme grabs a medium-chain fatty acid and prepares it for modification.
The catalytic cycle begins with the binding of a medium-chain fatty acid (6-12 carbons) to the active site of a cytochrome P450 enzyme, such as CYP4A11. The substrate is positioned such that the terminal methyl group (omega carbon) is oriented toward the heme iron. This binding induces a conformational change that facilitates the subsequent electron transfer steps.
Electron Transfer from NADPH
In simple terms: Electrons are delivered to the enzyme to activate oxygen.
The reaction requires reducing equivalents from NADPH, which are transferred via the redox partner NADPH--hemoprotein reductase (also known as cytochrome P450 reductase). The reductase shuttles electrons to the heme iron of the P450 enzyme, reducing it from the ferric (Fe3+) to the ferrous (Fe2+) state. This reduction is essential for binding and activating molecular oxygen.
Oxygen Activation and Hydroxylation
In simple terms: Oxygen is split, and one atom is inserted into the fatty acid.
Molecular oxygen binds to the reduced heme iron, forming a ferrous-dioxygen complex. A second electron transfer leads to the cleavage of the O-O bond, generating a highly reactive ferryl-oxo species (Compound I). This species abstracts a hydrogen atom from the omega carbon of the fatty acid, followed by oxygen rebound to form the omega-hydroxy fatty acid. The reaction consumes one molecule of O2 and produces one molecule of water.
Product Release and Enzyme Turnover
In simple terms: The modified fatty acid is released, and the enzyme resets.
After hydroxylation, the omega-hydroxy-medium-chain fatty acid is released from the active site. The enzyme returns to its resting state, ready for another catalytic cycle. The overall reaction stoichiometry is: omega-methyl-medium-chain fatty acid + O2 + reduced [NADPH--hemoprotein reductase] = omega-hydroxy-medium-chain fatty acid + H+ + H2O + oxidized [NADPH--hemoprotein reductase].
Regulation by PPAR/RXR
In simple terms: The amount of enzyme is controlled by nuclear receptors.
The expression of CYP4A genes, which encode medium-chain fatty acid omega-hydroxylases, is regulated by peroxisome proliferator-activated receptor alpha (PPARalpha) and retinoid X receptor (RXR). Upon ligand binding, PPARalpha forms a heterodimer with RXR and binds to peroxisome proliferator response elements (PPREs) in the promoter regions of target genes, increasing their transcription. This regulation links the activity to lipid sensing and energy metabolism.
Key Genes Involved in GO:0140981 medium-chain fatty acid omega-hydroxylase activity
The following genes encode enzymes or regulators directly involved in medium-chain fatty acid omega-hydroxylase activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CYP4A11 | Major lauric acid omega-hydroxylase in human liver | Key enzyme for medium-chain fatty acid metabolism; target for fatty liver disease |
| CYP4A22 | Omega-hydroxylase with activity toward medium-chain fatty acids | Potential compensatory role in CYP4A11 deficiency |
| CYP4B1 | Omega-hydroxylase active on medium-chain fatty acids | Enigmatic P450 at interface of xenobiotic and endobiotic metabolism |
| CYP4F2 | Omega-hydroxylase for various fatty acids | Involved in lipid mediator synthesis and inflammation |
| CYP4F3 | Omega-hydroxylase for leukotrienes and fatty acids | Role in inflammatory diseases |
| PPARA | Nuclear receptor regulating CYP4A expression | Master regulator of lipid metabolism; target for fibrates |
| RXRA | Heterodimer partner for PPARA | Essential for PPAR-mediated induction of CYP4A genes |
| ALKBGT | Bacterial alkane monooxygenase system | Model for omega-oxyfunctionalization in biotechnology |
| ALKL | Outer membrane transporter for AlkBGT | Facilitates substrate uptake in engineered E. coli |
| CYP2S1 | Orphan P450 with omega-1 hydroxylation activity | May contribute to polyunsaturated fatty acid metabolism |
| CYP4A1 | Rodent ortholog of CYP4A11 | Model for studying PPARalpha regulation in vivo |
| CYP4A2 | Rodent omega-hydroxylase | Used in experimental models of fatty liver |
| CYP4A3 | Rodent omega-hydroxylase | Studied in alcoholic liver disease models |
| CYP4A8 | Rat omega-hydroxylase | Model for kidney fatty acid metabolism |
| CYP4V2 | Omega-hydroxylase for very long-chain fatty acids | Mutations cause Bietti crystalline dystrophy |
| CYP4Z1 | Omega-hydroxylase expressed in breast tissue | Potential role in breast cancer |
| CYP4X1 | Omega-hydroxylase in brain | May influence brain lipid metabolism |
How Is medium-chain fatty acid omega-hydroxylase activity Regulated?
The activity of medium-chain fatty acid omega-hydroxylases is primarily regulated at the transcriptional level by the PPAR/RXR heterodimer. PPARalpha is activated by endogenous ligands such as fatty acids and by synthetic fibrates, leading to increased expression of CYP4A genes. This regulation ensures that omega-hydroxylation capacity matches lipid load. Additionally, post-translational mechanisms, including phosphorylation and interaction with redox partners, may modulate enzyme activity. In disease states such as alcoholic liver disease, changes in dietary fatty acids can alter omega-hydroxylation rates, suggesting nutritional regulation.
medium-chain fatty acid omega-hydroxylase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CYP4A11 | Fatty liver disease, lipotoxicity | Hepatocyte-specific knockout or overexpression in mice |
| CYP4A1 | Alcoholic liver disease | Rat model of chronic alcohol feeding |
| CYP4A8 | Nephrotic syndrome | PAN-induced nephrotic rat model |
| CYP4V2 | Bietti crystalline dystrophy | Retinal pigment epithelium cells with patient mutations |
| CYP4Z1 | Breast cancer | Breast cancer cell lines with knockdown or overexpression |
Fatty Liver Disease and Lipotoxicity
Medium-chain fatty acid omega-hydroxylase activity is critical for preventing lipotoxicity in the liver. When this activity is insufficient, medium-chain fatty acids accumulate, contributing to steatosis and hepatocellular damage. PPARalpha-mediated induction of CYP4A enzymes enhances omega-hydroxylation, reducing lipotoxicity. In fatty liver disease, impaired PPARalpha signaling may lead to decreased omega-hydroxylase activity, exacerbating lipid accumulation.
Alcoholic Liver Disease
Experimental alcoholic liver disease is associated with alterations in fatty acid omega-hydroxylation. Studies in animal models have shown that chronic alcohol consumption changes the activity of omega-hydroxylases, and these changes are influenced by dietary fatty acid composition. This suggests that omega-hydroxylation may play a role in the pathogenesis of alcohol-induced liver injury and could be a target for nutritional intervention.
Kidney Disorders
Disorders of fatty acid metabolism, including omega-hydroxylation, have been observed in the kidney of puromycin aminonucleoside (PAN)-induced nephrotic rats. This model exhibits changes in fatty acid oxidation and omega-hydroxylation, which may contribute to renal injury and proteinuria. The findings suggest that medium-chain fatty acid omega-hydroxylase activity is relevant to kidney pathophysiology.
Cancer and Other Diseases
Some CYP4 enzymes with omega-hydroxylase activity, such as CYP4Z1 and CYP4A11, have been implicated in cancer progression, though the exact mechanisms remain under investigation. Additionally, mutations in CYP4V2, which has omega-hydroxylase activity toward very long-chain fatty acids, cause Bietti crystalline dystrophy, a retinal degenerative disease. These examples highlight the diverse disease relevance of omega-hydroxylation.
From medium-chain fatty acid omega-hydroxylase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of CYP4A11 loss on medium-chain fatty acid metabolism? | CYP4A11 knockout hepatocytes or mice |
| How does a specific point mutation in CYP4A11 affect catalytic activity? | Point-mutation knock-in via CRISPR in cell lines |
| Can we tag CYP4A11 to visualize its subcellular localization? | Knock-in of fluorescent tag (e.g., GFP) at endogenous locus |
| Does overexpression of CYP4A11 protect against lipotoxicity? | CYP4A11 overexpression in hepatocytes or mice |
| What is the role of PPARalpha in regulating omega-hydroxylase activity? | PPARalpha knockout mice |
| Can microbial AlkBGT be engineered for improved omega-hydroxylation? | E. coli expressing AlkBGT and AlkL |
How to Study the medium-chain fatty acid omega-hydroxylase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS/MS | Omega-hydroxy fatty acid products | Quantification of enzyme activity in microsomes |
| RNA-seq | Transcript levels of CYP4A genes | Assessing transcriptional regulation by PPARalpha |
| Untargeted metabolomics | Global metabolic changes | Discovering novel substrates and pathways |
| CRISPR knockout | Loss-of-function effects | Determining gene necessity in cell models |
| CRISPR knock-in | Tagged or mutant protein expression | Visualizing localization or studying point mutations |
| Overexpression | Gain-of-function effects | Testing protective or detrimental roles |
| Microsomal incubation | Enzyme kinetics | Measuring Vmax and Km for substrates |
| Western blot | Protein expression levels | Validating knockout or overexpression |
Enzymatic Activity Assays
Medium-chain fatty acid omega-hydroxylase activity can be measured using radiolabeled or fluorescent substrates, such as lauric acid, followed by HPLC or LC-MS analysis of the omega-hydroxy product. These assays are typically performed with microsomes or purified recombinant enzymes in the presence of NADPH and a NADPH-regenerating system.
Gene Expression Analysis
Quantitative RT-PCR and RNA-seq can be used to measure the expression levels of CYP4A genes and their regulators (e.g., PPARalpha, RXRalpha) under different conditions. This helps determine whether changes in activity are due to transcriptional regulation.
Metabolomics and Lipidomics
Untargeted metabolomics and lipidomics can identify and quantify omega-hydroxy fatty acids and other metabolites in biological samples, providing a comprehensive view of the impact of omega-hydroxylase activity on cellular metabolism. This approach can reveal novel substrates and pathways.
CRISPR-Based Genetic Models
CRISPR/Cas9 technology enables the generation of knockout, knock-in, and point-mutation cell lines and animal models to study the function of specific omega-hydroxylases. These models are essential for establishing causality between enzyme activity and physiological outcomes.
How CRISPR Can Be Used to Study GO:0140981 medium-chain fatty acid omega-hydroxylase activity
Knockout
CRISPR/Cas9-mediated knockout of CYP4A11 or other omega-hydroxylase genes in human cell lines (e.g., HepG2, HEK293) can abolish enzyme activity, allowing researchers to study the consequences of loss of function on lipid metabolism and cellular stress. Knockout mouse models can further elucidate the role of these enzymes in vivo.
Point Mutation
Point mutations identified in patients or designed to probe catalytic residues can be introduced via CRISPR-based prime editing or homology-directed repair. These models help determine how specific amino acid changes affect substrate binding, catalytic efficiency, or interactions with redox partners.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins (e.g., GFP) at the endogenous locus enables visualization and purification of omega-hydroxylases without overexpression artifacts. This approach is valuable for studying subcellular localization and protein-protein interactions.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression can increase the expression of omega-hydroxylases to study gain-of-function effects, such as protection against lipotoxicity or enhanced drug metabolism. Overexpression models are also useful for producing recombinant enzymes for structural and biochemical studies.
How EDITGENE Supports medium-chain fatty acid omega-hydroxylase activity Research
Researchers studying medium-chain fatty acid omega-hydroxylase activity-related genes often need to determine whether a candidate gene is causally involved in lipid metabolism, disease progression, or drug response. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models, enabling functional validation and mechanistic studies.
Contact EDITGENE today to design your custom CRISPR model for medium-chain fatty acid omega-hydroxylase activity research.
Frequently Asked Questions About medium-chain fatty acid omega-hydroxylase activity
What is medium-chain fatty acid omega-hydroxylase activity?
It is an enzymatic activity (GO:0140981) that adds a hydroxyl group to the terminal carbon of medium-chain fatty acids (6-12 carbons), using oxygen and NADPH.
What genes are involved in medium-chain fatty acid omega-hydroxylase activity?
Key genes include CYP4A11, CYP4A22, CYP4B1, CYP4F2, and their regulators PPARA and RXRA [1,3,6].
Which enzyme is the major lauric acid omega-hydroxylase in human liver?
CYP4A11 is the major lauric acid omega-hydroxylase in human liver microsomes.
How is medium-chain fatty acid omega-hydroxylase activity regulated?
It is primarily regulated at the transcriptional level by PPARalpha/RXR heterodimers, which induce CYP4A gene expression in response to fatty acids or fibrates.
What diseases are associated with defects in medium-chain fatty acid omega-hydroxylase activity?
Fatty liver disease, alcoholic liver injury, nephrotic syndrome, and Bietti crystalline dystrophy have been linked to altered omega-hydroxylase activity [1,2,5].
Can CRISPR be used to study medium-chain fatty acid omega-hydroxylase activity?
Yes, CRISPR knockout, knock-in, and point mutation models enable precise functional studies of genes encoding these enzymes.
What are the substrates of medium-chain fatty acid omega-hydroxylase?
Medium-chain fatty acids with aliphatic tails of 6 to 12 carbons, such as lauric acid (12:0).
What is the reaction catalyzed by GO:0140981?
An omega-methyl-medium-chain fatty acid + O2 + reduced [NADPH--hemoprotein reductase] = an omega-hydroxy-medium-chain fatty acid + H+ + H2O + oxidized [NADPH--hemoprotein reductase].
How can I measure medium-chain fatty acid omega-hydroxylase activity in the lab?
Activity can be measured using LC-MS/MS or HPLC to detect omega-hydroxy fatty acid products after incubation with microsomes or recombinant enzymes.
Are there microbial enzymes with medium-chain fatty acid omega-hydroxylase activity?
Yes, the AlkBGT system from Pseudomonas putida catalyzes omega-oxyfunctionalization of medium-chain fatty acids and is used in biotechnology.
Conclusion
Medium-chain fatty acid omega-hydroxylase activity (GO:0140981) is a vital enzymatic function in lipid metabolism, primarily mediated by cytochrome P450 enzymes such as CYP4A11. Its role in preventing lipotoxicity and its dysregulation in liver and kidney diseases make it a compelling target for therapeutic development. Advances in CRISPR-based models and analytical techniques are accelerating our understanding of this activity and its broader physiological impact. EDITGENE's suite of CRISPR services supports researchers in dissecting the genetic and molecular mechanisms underlying this important activity.
References
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- 2. Amet Y et al.. 1998. Fatty acid omega- and (omega-1)-hydroxylation in experimental alcoholic liver disease: relationship to different dietary fatty acids.. Alcohol Clin Exp Res 22(7):1493-500 PMID: 9802534
- 3. Powell PK et al.. 1996. Identification of CYP4A11 as the major lauric acid omega-hydroxylase in human liver microsomes.. Arch Biochem Biophys 335(1):219-26 PMID: 8914854
- 4. Fekry MI et al.. 2019. A Role for the Orphan Human Cytochrome P450 2S1 in Polyunsaturated Fatty Acid ω-1 Hydroxylation Using an Untargeted Metabolomic Approach.. Drug Metab Dispos 47(11):1325-1332 PMID: 31511258
- 5. Muroya Y et al.. 2012. Disorder of fatty acid metabolism in the kidney of PAN-induced nephrotic rats.. Am J Physiol Renal Physiol 303(7):F1070-9 PMID: 22874759
- 6. Baer BR et al.. 2006. CYP4B1: an enigmatic P450 at the interface between xenobiotic and endobiotic metabolism.. Drug Metab Rev 38(3):451-76 PMID: 16877261
- 7. Brinkman EK et al.. 2012. A toolkit to enable hydrocarbon conversion in aqueous environments.. J Vis Exp PMID: 23052445
- 8. van Nuland YM et al.. 2016. Application of AlkBGT and AlkL from Pseudomonas putida GPo1 for Selective Alkyl Ester ω-Oxyfunctionalization in Escherichia coli.. Appl Environ Microbiol 82(13):3801-3807 PMID: 27084021
