GO:0008458 carnitine O-octanoyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008458 describes the enzymatic activity that transfers an octanoyl group from octanoyl-CoA to (R)-carnitine, producing O-octanoyl-(R)-carnitine and CoA.
• The enzyme responsible, CROT (carnitine O-octanoyltransferase), is a peroxisomal and mitochondrial enzyme that participates in fatty acid oxidation by shuttling medium-chain acylcarnitines.
• CROT is a direct p53 target gene; its induction supports oxidative metabolism and cell survival during nutrient starvation.
• CROT overactivation in peroxisomes contributes to chemoresistance in non-small cell lung cancer by modulating fatty acid oxidation, Nrf2 signaling, and ferroptosis resistance.
• CROT and the related carnitine acyltransferase CRAT promote metastasis in melanoma, highlighting a role in cancer progression.
• Dysregulated carnitine metabolism, including CROT activity, is linked to vascular calcification, obesity-related nonalcoholic fatty liver disease, and metabolic responses to pemafibrate.
Description
Carnitine O-octanoyltransferase activity (GO:0008458) is a molecular function defined by the reversible transfer of an octanoyl group from octanoyl-CoA to (R)-carnitine, yielding O-octanoyl-(R)-carnitine and coenzyme A. This reaction is a key step in the carnitine shuttle system that facilitates the transport and oxidation of medium-chain fatty acids within peroxisomes and mitochondria. The enzyme responsible for this activity, CROT, has emerged as a critical node in lipid metabolism, with roles in energy homeostasis, oxidative stress responses, and disease pathogenesis. Researchers study GO:0008458 to understand how cells adapt to nutrient availability, how peroxisomal and mitochondrial fatty acid oxidation are coordinated, and how dysregulation of this activity contributes to cancer, cardiovascular disease, and metabolic disorders.
carnitine O-octanoyltransferase activity At A Glance
| GO ID | GO:0008458 |
|---|---|
| GO term | carnitine O-octanoyltransferase activity |
| Ontology | molecular_function |
| Synonym | carnitine medium-chain acyltransferase activity; easily solubilized mitochondrial carnitine palmitoyltransferase; medium-chain/long-chain carnitine acyltransferase activity; octanoyl-CoA:L-carnitine O-octanoyltransferase activity; overt mitochondrial carnitine palmitoyltransferase |
| Major function | Catalyzes the reversible transfer of octanoyl groups from octanoyl-CoA to (R)-carnitine, producing O-octanoyl-(R)-carnitine and CoA, a key step in fatty acid oxidation. |
| Enzyme | CROT (carnitine O-octanoyltransferase), a peroxisomal and mitochondrial enzyme. |
| Substrates | (R)-carnitine and octanoyl-CoA. |
| Products | O-octanoyl-(R)-carnitine and coenzyme A. |
| Cellular location | Peroxisomes and mitochondria. |
What Is GO:0008458?
According to the Gene Ontology, carnitine O-octanoyltransferase activity (GO:0008458) catalyzes the chemical reaction: (R)-carnitine + octanoyl-CoA = CoA + O-octanoyl-(R)-carnitine. In other words, it is the enzyme activity that attaches an eight-carbon fatty acid chain (octanoyl group) to carnitine, forming acylcarnitine, which is essential for fatty acid transport and oxidation. This activity is also known by synonyms such as carnitine medium-chain acyltransferase activity, medium-chain/long-chain carnitine acyltransferase activity, and octanoyl-CoA:L-carnitine O-octanoyltransferase activity.
Why Is carnitine O-octanoyltransferase activity Important in Cell Biology?
Carnitine O-octanoyltransferase activity is essential for medium-chain fatty acid metabolism and cellular energy homeostasis. By converting octanoyl-CoA to octanoylcarnitine, it enables the transport of fatty acids across organelle membranes for beta-oxidation. This activity is directly regulated by the tumor suppressor p53 and supports cell survival under nutrient starvation, linking metabolism to stress responses. Dysregulation of CROT contributes to diverse pathologies, including vascular calcification, cancer chemoresistance, melanoma metastasis, and metabolic liver disease, making it a potential therapeutic target and biomarker.
• Enables peroxisomal and mitochondrial fatty acid oxidation by shuttling medium-chain acylcarnitines.
• Is a direct p53 target gene that promotes oxidative metabolism and survival during nutrient starvation.
• Overactivation in peroxisomes confers chemoresistance in non-small cell lung cancer via fatty acid oxidation-Nrf2-ferroptosis resistance.
• CROT and CRAT promote metastasis in melanoma.
• Contributes to vascular calcification by promoting fatty acid metabolism and mitochondrial dysfunction.
• Associated with obesity-related nonalcoholic fatty liver disease through Notch signaling and lipid metabolism deregulation.
• Carnitine metabolism, including CROT activity, is a central metabolic axis of pemafibrate action.
• Provides a potential target for modulating ferroptosis sensitivity in cancer therapy.
• Serves as a biomarker for metabolic disorders and cancer progression.
• Offers a model to study peroxisome-mitochondria crosstalk in health and disease.
What Happens During carnitine O-octanoyltransferase activity?
Substrate recognition and binding
In simple terms: The enzyme grabs octanoyl-CoA and carnitine to start the reaction.
CROT specifically binds (R)-carnitine and octanoyl-CoA. The enzyme's active site accommodates the medium-chain acyl group of octanoyl-CoA and the hydroxyl group of carnitine, positioning them for catalysis. This binding is the first step in the carnitine shuttle, which is critical for fatty acid oxidation.
Catalytic transfer of the octanoyl group
In simple terms: The enzyme moves the octanoyl group from CoA to carnitine.
The catalytic mechanism involves the transfer of the octanoyl moiety from octanoyl-CoA to the hydroxyl group of (R)-carnitine, forming O-octanoyl-(R)-carnitine and releasing free coenzyme A. This reaction is reversible and is part of the carnitine acyltransferase family, which includes CROT and CRAT.
Product release and shuttle function
In simple terms: The product, octanoylcarnitine, is released to transport fatty acids.
After catalysis, O-octanoyl-(R)-carnitine is released and can be transported across peroxisomal or mitochondrial membranes, where it is converted back to octanoyl-CoA for beta-oxidation. This shuttle is essential for medium-chain fatty acid oxidation and energy production.
Integration with peroxisomal and mitochondrial metabolism
In simple terms: The reaction connects peroxisomes and mitochondria for fat burning.
CROT activity is localized in peroxisomes and mitochondria, where it facilitates the exchange of acylcarnitines and acyl-CoAs. In peroxisomes, CROT overactivation promotes fatty acid oxidation and modulates Nrf2 signaling, affecting ferroptosis resistance in cancer cells. In mitochondria, it supports oxidative metabolism under nutrient stress.
Regulation by p53 and nutrient status
In simple terms: The reaction is turned on by p53 when nutrients are low.
CROT is a direct transcriptional target of p53. Under nutrient starvation, p53 induces CROT expression, which enhances oxidative metabolism and promotes cell survival. This regulation links carnitine O-octanoyltransferase activity to cellular stress responses and metabolic adaptation.
Key Genes Involved in GO:0008458 carnitine O-octanoyltransferase activity
The following genes and proteins are directly involved in or regulate carnitine O-octanoyltransferase activity and its associated pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CROT | Encodes carnitine O-octanoyltransferase, the enzyme catalyzing GO:0008458 | Central to fatty acid oxidation, p53 target, cancer and metabolic disease |
| CRAT | Carnitine acetyltransferase, related acyltransferase | Cooperates with CROT in peroxisomal acyl-carnitine shuttle, promotes melanoma metastasis |
| TP53 | Tumor suppressor, transcription factor | Directly induces CROT expression under nutrient starvation |
| PPARA | Peroxisome proliferator-activated receptor alpha | Regulates peroxisomal gene transcription including CROT |
| PPARGC1A | PGC-1alpha, coactivator of PPARA | Controls peroxisomal gene expression and mitochondrial biogenesis |
| Nrf2 (NFE2L2) | Transcription factor regulating antioxidant response | Modulated by CROT overactivation in chemoresistant NSCLC |
| NOTCH | Signaling pathway regulating lipid metabolism | Deregulated in obesity-related NAFLD, linked to CROT |
| ACOX1 | Peroxisomal acyl-CoA oxidase | First step of peroxisomal fatty acid oxidation, functionally linked to CROT |
| CPT1A | Mitochondrial carnitine palmitoyltransferase 1 | Long-chain fatty acid transport, related to carnitine shuttle |
| CPT2 | Mitochondrial carnitine palmitoyltransferase 2 | Inner membrane carnitine shuttle, related to CROT function |
| SLC25A20 | Carnitine-acylcarnitine translocase | Transports acylcarnitines across inner mitochondrial membrane |
| HADHA | Mitochondrial trifunctional protein alpha | Beta-oxidation of long-chain fatty acids, linked to CROT pathway |
| ACADM | Medium-chain acyl-CoA dehydrogenase | Beta-oxidation of medium-chain fatty acids, related to CROT substrates |
| FASN | Fatty acid synthase | De novo lipogenesis, may influence CROT substrate availability |
| SCD1 | Stearoyl-CoA desaturase 1 | Fatty acid desaturation, linked to lipid metabolism |
| CPT1B | Carnitine palmitoyltransferase 1B | Muscle isoform, related to carnitine shuttle |
| SLC22A5 | Carnitine transporter OCTN2 | Cellular carnitine uptake, affects substrate availability for CROT |
| PDK4 | Pyruvate dehydrogenase kinase 4 | Regulates metabolic switch, may interact with CROT pathway |
How Is carnitine O-octanoyltransferase activity Regulated?
Carnitine O-octanoyltransferase activity is regulated at multiple levels. Transcriptionally, CROT is a direct p53 target gene; p53 binds to the CROT promoter and induces its expression under nutrient starvation, promoting oxidative metabolism and cell survival. Peroxisomal gene transcription, including CROT, is controlled by PPARA and PPARGC1A; lysosomal inhibition suppresses PPARA and PPARGC1A levels, thereby attenuating peroxisomal gene transcription. In obesity and nonalcoholic fatty liver disease, Notch signaling deregulation is associated with altered lipid metabolism, potentially affecting CROT expression. Additionally, microRNAs have been implicated in metabolic regulation, including carnitine metabolism. Post-translational modifications and substrate availability further modulate CROT activity, but specific mechanisms require further investigation.
carnitine O-octanoyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CROT | Non-small cell lung cancer chemoresistance | CROT knockout or overexpression in NSCLC cell lines, ferroptosis assays |
| CROT | Vascular calcification | CROT knockout in vascular smooth muscle cells, calcification assays |
| CROT | Melanoma metastasis | CROT knockout in melanoma cell lines, metastasis mouse models |
| CROT | Nonalcoholic fatty liver disease | Liver-specific CROT knockout mice, high-fat diet |
| CROT | Nutrient starvation survival | CROT knockout cells under starvation, p53 activation |
CROT in cancer chemoresistance and metastasis
CROT overactivation within peroxisomes confers chemoresistance to non-small cell lung cancer by targeting the fatty acid oxidation-Nrf2-ferroptosis resistance axis. In melanoma, the peroxisomal acyl-carnitine shuttle regulators CROT and CRAT promote metastasis, suggesting that CROT activity supports cancer cell survival and dissemination. These findings highlight CROT as a potential therapeutic target to overcome chemoresistance and inhibit metastasis.
CROT in vascular calcification and cardiovascular disease
CROT is a novel contributing factor in vascular calcification via promoting fatty acid metabolism and mitochondrial dysfunction. Elevated CROT activity may drive pathological calcification of vascular smooth muscle cells, linking carnitine O-octanoyltransferase activity to cardiovascular disease progression.
CROT in metabolic liver disease and obesity
Hepatocyte Notch signaling deregulation is related to lipid metabolism in women with obesity and nonalcoholic fatty liver disease, where CROT expression may be altered. Additionally, serum metabolomics reveals carnitine metabolism as a possible central metabolic axis of pemafibrate action, indicating that CROT activity is relevant to lipid-lowering therapies.
CROT as a p53 target in nutrient stress and survival
CROT is a p53 target that promotes oxidative metabolism and cell survival following nutrient starvation. This positions CROT at the intersection of tumor suppression and metabolic adaptation, with implications for cancer therapy and metabolic disorders.
From carnitine O-octanoyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does CROT loss affect fatty acid oxidation? | CROT knockout cell lines (e.g., HepG2, HeLa) |
| Does CROT overexpression promote chemoresistance? | CROT overexpression in NSCLC cells, ferroptosis induction |
| Does CROT point mutation alter catalytic activity? | CRISPR point mutation knock-in of catalytic residues |
| Does CROT tagging affect localization? | Knock-in of fluorescent or epitope tags at endogenous CROT locus |
| Does CROT regulate vascular calcification? | CROT knockout in vascular smooth muscle cells |
| Does CROT mediate melanoma metastasis? | CROT knockout in melanoma cells, xenograft models |
How to Study the carnitine O-octanoyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic activity assay | CROT catalytic activity | Quantify octanoylcarnitine production in cell lysates |
| Metabolomics | Carnitine and acylcarnitine levels | Serum or tissue profiling in metabolic disease |
| RNA-seq | CROT mRNA expression | Transcriptional regulation by p53 or PPARA |
| Western blot | CROT protein levels | Validation of knockout or overexpression |
| Immunofluorescence | CROT subcellular localization | Peroxisomal vs mitochondrial distribution |
| CRISPR knockout | Loss of CROT function | Phenotypic studies in cancer or metabolic cells |
| CRISPR knock-in | Tagged or mutant CROT | Localization and catalytic residue analysis |
| Proteomics | Protein interactions and modifications | Identify CROT partners in fatty acid oxidation |
Enzymatic activity assays
Carnitine O-octanoyltransferase activity can be measured using spectrophotometric or radiometric assays that monitor the formation of O-octanoyl-(R)-carnitine or release of CoA from octanoyl-CoA. These assays are typically performed with cell or tissue lysates and can be coupled to downstream reactions for detection.
Metabolomics and lipidomics
Serum or cellular metabolomics can quantify carnitine and acylcarnitine species, including octanoylcarnitine, to infer CROT activity. Lipidomics further profiles fatty acid oxidation intermediates and membrane lipids affected by CROT.
Gene expression and transcriptomics
RNA-seq and qPCR are used to measure CROT mRNA levels in response to p53 activation, nutrient starvation, or PPARA/PPARGC1A modulation. These methods help establish transcriptional regulation of CROT in disease models.
Proteomics and protein interaction studies
Mass spectrometry-based proteomics can identify CROT interaction partners and post-translational modifications. Immunoprecipitation followed by western blotting validates interactions with proteins such as CRAT or mitochondrial carriers.
How CRISPR Can Be Used to Study GO:0008458 carnitine O-octanoyltransferase activity
Knockout
CRISPR-Cas9 knockout of CROT is used to eliminate carnitine O-octanoyltransferase activity, enabling studies of its role in fatty acid oxidation, cell survival, and disease phenotypes. For example, CROT knockout in cancer cells reduces chemoresistance and alters ferroptosis sensitivity.
Point Mutation
CRISPR point mutation knock-in can introduce catalytic dead mutations or disease-associated variants into the CROT gene to dissect the enzymatic mechanism and substrate specificity. Such models help distinguish catalytic activity from non-enzymatic functions.
Knock-in
Knock-in of fluorescent or epitope tags at the endogenous CROT locus allows real-time tracking of CROT localization and dynamics in peroxisomes and mitochondria. This approach preserves native regulation and expression levels.
Overexpression
CRISPR activation or lentiviral overexpression of CROT is used to model CROT overactivation observed in chemoresistant cancers and vascular calcification. Overexpression studies reveal downstream effects on Nrf2 signaling, ferroptosis, and mitochondrial function.
How EDITGENE Supports carnitine O-octanoyltransferase activity Research
Researchers studying carnitine O-octanoyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in fatty acid oxidation, metabolic disease, or cancer. EDITGENE provides comprehensive CRISPR gene editing services to create precise cellular models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for carnitine O-octanoyltransferase activity research.
Frequently Asked Questions About carnitine O-octanoyltransferase activity
What is carnitine O-octanoyltransferase activity?
Carnitine O-octanoyltransferase activity (GO:0008458) is the enzymatic activity that transfers an octanoyl group from octanoyl-CoA to (R)-carnitine, forming O-octanoyl-(R)-carnitine and CoA, a key step in fatty acid oxidation.
What gene encodes carnitine O-octanoyltransferase?
The CROT gene encodes the enzyme carnitine O-octanoyltransferase, which catalyzes this activity.
What is the role of CROT in cancer?
CROT overactivation in peroxisomes confers chemoresistance to non-small cell lung cancer by targeting the fatty acid oxidation-Nrf2-ferroptosis resistance axis, and CROT promotes metastasis in melanoma.
How is CROT regulated?
CROT is a direct p53 target gene induced under nutrient starvation, and its transcription is also controlled by PPARA and PPARGC1A.
What diseases are associated with CROT?
CROT is associated with vascular calcification, non-small cell lung cancer chemoresistance, melanoma metastasis, and nonalcoholic fatty liver disease.
What are the substrates of carnitine O-octanoyltransferase?
The substrates are (R)-carnitine and octanoyl-CoA, and the products are O-octanoyl-(R)-carnitine and coenzyme A.
Where is CROT located in the cell?
CROT is localized in peroxisomes and mitochondria, where it facilitates fatty acid transport and oxidation.
How can I study carnitine O-octanoyltransferase activity in the lab?
You can use enzymatic activity assays, metabolomics, RNA-seq, and CRISPR knockout or overexpression models to study CROT function.
What is the connection between CROT and ferroptosis?
CROT overactivation promotes ferroptosis resistance in cancer cells by modulating fatty acid oxidation and Nrf2 signaling.
Does CROT affect vascular calcification?
Yes, CROT contributes to vascular calcification by promoting fatty acid metabolism and mitochondrial dysfunction.
Conclusion
Carnitine O-octanoyltransferase activity (GO:0008458) is a fundamental enzymatic function in fatty acid metabolism, catalyzed by CROT. Its regulation by p53 and PPARA/PPARGC1A links it to nutrient sensing and metabolic adaptation. Dysregulation of CROT contributes to cancer chemoresistance, melanoma metastasis, vascular calcification, and metabolic liver disease, making it a promising target for therapeutic intervention. Continued research using CRISPR models and multi-omics approaches will further elucidate its mechanistic roles and clinical potential.
References
- 1. Sanford JD et al.. 2023. Carnitine o-octanoyltransferase is a p53 target that promotes oxidative metabolism and cell survival following nutrient starvation.. J Biol Chem 299(7):104908 PMID: 37307919
- 2. Okui T et al.. 2021. CROT (Carnitine O-Octanoyltransferase) Is a Novel Contributing Factor in Vascular Calcification via Promoting Fatty Acid Metabolism and Mitochondrial Dysfunction.. Arterioscler Thromb Vasc Biol 41(2):755-768 PMID: 33356393
- 3. Hua C et al.. 2025. CROT overactivation within peroxisomes confers chemoresistance to non-small cell lung cancer by targeting fatty acid oxidation-Nrf2-ferroptosis resistance axis.. Pharmacol Res 220:107911 PMID: 40818823
- 4. Qian C et al.. 2026. Serum Metabolomics Reveals Carnitine Metabolism as a Possible Central Metabolic Axis of Pemafibrate Action.. Int J Mol Sci 27(14) PMID: 42511595
- 5. Lasheras-Otero I et al.. 2023. The Regulators of Peroxisomal Acyl-Carnitine Shuttle CROT and CRAT Promote Metastasis in Melanoma.. J Invest Dermatol 143(2):305-316.e5 PMID: 36058299
- 6. Rottiers V et al.. 2011. MicroRNAs in metabolism and metabolic diseases.. Cold Spring Harb Symp Quant Biol 76:225-33 PMID: 22156303
- 7. Tan HWS et al.. 2019. Lysosomal inhibition attenuates peroxisomal gene transcription via suppression of PPARA and PPARGC1A levels.. Autophagy 15(8):1455-1459 PMID: 31032705
- 8. Auguet T et al.. 2020. Hepatocyte Notch Signaling Deregulation Related to Lipid Metabolism in Women with Obesity and Nonalcoholic Fatty Liver.. Obesity (Silver Spring) 28(8):1487-1493 PMID: 32657010
