GO:0004095 carnitine O-palmitoyltransferase activity: Mechanism, Genes and Research Methods

Research-grade guide for scientists and biopharma professionals

Key Takeaways

GO:0004095 carnitine O-palmitoyltransferase activity catalyzes the reversible transfer of a palmitoyl group from palmitoyl-CoA to L-carnitine, forming L-palmitoylcarnitine and CoA.
This activity is essential for mitochondrial long-chain fatty acid oxidation, as it converts long-chain acyl-CoAs into acylcarnitines that can cross the mitochondrial membranes.
CPT1A, CPT1B, CPT1C, CPT2, and related carnitine acyltransferases are the major enzymes annotated with this activity, with distinct subcellular localizations and tissue distributions.
Dysregulation of carnitine O-palmitoyltransferase activity is linked to metabolic disorders, hepatic steatosis, fibrosis, and cancer stemness.
Pharmacological and genetic modulation of CPT1 activity can ameliorate diet-induced obesity, hepatic steatosis, and fibrosis in preclinical models.
CRISPR-based knockout, point-mutation, knock-in, and overexpression models enable precise interrogation of CPT1/CPT2 function in metabolic and disease contexts.

Description

Carnitine O-palmitoyltransferase activity (GO:0004095) is a molecular function that catalyzes the reversible transfer of a palmitoyl group from palmitoyl-CoA to L-carnitine, yielding L-palmitoylcarnitine and coenzyme A. This reaction is the first committed step in the mitochondrial carnitine shuttle, a system required for the transport of long-chain fatty acids into the mitochondrial matrix for beta-oxidation. Because long-chain acyl-CoAs cannot directly cross the inner mitochondrial membrane, their conversion to acylcarnitines by carnitine O-palmitoyltransferase activity is indispensable for energy production from fat. The enzyme activity is represented by multiple isoforms, including CPT1A, CPT1B, CPT1C, and CPT2, which differ in tissue expression, subcellular localization, and regulatory properties. Beyond its canonical role in fatty acid oxidation, this activity influences lipid signaling, reactive oxygen species homeostasis, and cellular stress responses. Consequently, carnitine O-palmitoyltransferase activity has emerged as a therapeutic target in metabolic diseases, fibrosis, and cancer. Researchers studying this activity require reliable models to dissect isoform-specific functions and to evaluate candidate drugs that modulate the carnitine shuttle.

carnitine O-palmitoyltransferase activity At A Glance

GO ID GO:0004095
GO term carnitine O-palmitoyltransferase activity
Ontology molecular_function
Synonym carnitine palmitoyltransferase activity; CPT; carnitine palmitoyltransferase I; carnitine palmitoyltransferase II; palmitoyl-CoA:L-carnitine O-palmitoyltransferase activity
Major function Catalyzes the reversible transfer of palmitoyl from palmitoyl-CoA to L-carnitine, forming L-palmitoylcarnitine and CoA; essential for mitochondrial long-chain fatty acid oxidation.
Reaction palmitoyl-CoA + L-carnitine = CoA + L-palmitoylcarnitine
Enzyme class Acyltransferase (EC 2.3.1.21)
Subcellular location Mitochondrial outer membrane (CPT1) and inner membrane (CPT2)
Tissue distribution CPT1A: liver, kidney, brain; CPT1B: muscle, heart, brown adipose tissue; CPT1C: brain; CPT2: ubiquitous

What Is GO:0004095?

According to the Gene Ontology, carnitine O-palmitoyltransferase activity (GO:0004095) is defined as the catalysis of the reaction: palmitoyl-CoA + L-carnitine = CoA + L-palmitoylcarnitine. In other words, it is an acyltransferase activity that transfers a palmitoyl group from palmitoyl-coenzyme A to the hydroxyl group of L-carnitine, producing palmitoylcarnitine and free coenzyme A. This activity is synonymous with carnitine palmitoyltransferase activity, CPT, and several other names including carnitine palmitoyltransferase I and II, reflecting the multiple isoforms that catalyze this reaction.

Why Is carnitine O-palmitoyltransferase activity Important in Cell Biology?

Carnitine O-palmitoyltransferase activity is a central node in energy metabolism because it gates the entry of long-chain fatty acids into mitochondria for beta-oxidation. This activity is also a key determinant of metabolic flexibility, and its dysregulation contributes to insulin resistance, hepatic steatosis, and obesity. In addition, emerging evidence links this activity to fibrosis, cancer stemness, and ferroptosis, making it a promising therapeutic target. Understanding its regulation and isoform-specific functions is therefore critical for both basic metabolism research and translational drug discovery.
Essential for mitochondrial long-chain fatty acid oxidation and ATP production.
Regulates metabolic flexibility and whole-body energy homeostasis.
Dysregulated in obesity, type 2 diabetes, and non-alcoholic fatty liver disease.
Inhibition of CPT1A in hepatic stellate cells reduces fibrosis in preclinical models.
CPT1A-mediated succinylation of MFF supports ovarian cancer stem cell maintenance.
Pharmacological activation of hepatic CPT1 ameliorates diet-induced obesity and steatosis.
Mutations in CPT1A and CPT2 cause inherited carnitine palmitoyltransferase deficiencies.
Carnitine supplementation may influence muscle bioenergetics via this activity.
Serves as a target for chemoproteomics and drug discovery.
Provides a mechanistic link between lipid metabolism and ferroptosis in fibrosis.

What Happens During carnitine O-palmitoyltransferase activity?

Substrate recognition and binding
In simple terms: The enzyme grabs palmitoyl-CoA and L-carnitine and holds them in the right orientation.
Carnitine O-palmitoyltransferase enzymes bind palmitoyl-CoA and L-carnitine in a sequential manner. The acyl-CoA substrate is recognized through its long hydrophobic acyl chain and the CoA moiety, while L-carnitine binds via its trimethylammonium and hydroxyl groups. Structural and kinetic studies indicate that CPT1 isoforms are inhibited by malonyl-CoA, which binds at a distinct site and prevents acyl-CoA access.
Catalytic transfer of the palmitoyl group
In simple terms: The enzyme moves the palmitoyl group from CoA to carnitine, making palmitoylcarnitine.
The catalytic mechanism involves nucleophilic attack of the L-carnitine hydroxyl group on the thioester carbonyl of palmitoyl-CoA, forming a tetrahedral intermediate and releasing CoA. The reaction is reversible, but in vivo the subsequent transport and beta-oxidation steps drive flux toward palmitoylcarnitine formation.
Product release and shuttle coupling
In simple terms: The product, palmitoylcarnitine, is released and then shuttled into mitochondria.
After catalysis, L-palmitoylcarnitine is released from the active site and transported across the inner mitochondrial membrane by carnitine-acylcarnitine translocase (CACT). Inside the matrix, CPT2 catalyzes the reverse reaction to regenerate palmitoyl-CoA for beta-oxidation.
Isoform-specific regulation
In simple terms: Different versions of the enzyme are controlled differently in different tissues.
CPT1A is inhibited by malonyl-CoA and is highly expressed in liver, kidney, and brain; CPT1B is more sensitive to malonyl-CoA inhibition and predominates in muscle and heart; CPT1C is brain-specific and has low catalytic activity but roles in ceramide metabolism and energy sensing. CPT2 is not inhibited by malonyl-CoA and is ubiquitously expressed.
Integration with cellular metabolic state
In simple terms: The enzyme activity changes depending on whether the cell needs more energy from fat.
Carnitine O-palmitoyltransferase activity is regulated by nutritional and hormonal signals. Insulin suppresses CPT1A activity, whereas fasting, glucagon, and AMPK activation increase it. Malonyl-CoA, a product of fatty acid synthesis, acts as a potent inhibitor of CPT1A and CPT1B, linking fatty acid synthesis and oxidation.

Key Genes Involved in GO:0004095 carnitine O-palmitoyltransferase activity

The following genes encode enzymes or regulators directly associated with carnitine O-palmitoyltransferase activity.
GeneMajor RoleResearch Relevance
CPT1A Liver-type carnitine palmitoyltransferase 1; catalyzes palmitoyl-CoA to palmitoylcarnitine; inhibited by malonyl-CoA Target in obesity, steatosis, fibrosis, and cancer; knockout and overexpression models available
CPT1B Muscle-type carnitine palmitoyltransferase 1; high expression in heart and skeletal muscle Role in cardiac and skeletal muscle fatty acid oxidation; knockout models show impaired exercise capacity
CPT1C Brain-specific carnitine palmitoyltransferase 1; low catalytic activity; involved in ceramide metabolism and energy sensing Implicated in neuronal function and cancer; knockout models show metabolic and behavioral phenotypes
CPT2 Inner mitochondrial membrane carnitine palmitoyltransferase 2; catalyzes reverse reaction to regenerate acyl-CoA Mutations cause CPT2 deficiency; knockout models are lethal or show severe metabolic stress
SLC25A20 Carnitine-acylcarnitine translocase (CACT); transports acylcarnitines across inner mitochondrial membrane Mutations cause CACT deficiency; relevant for shuttle function
ACADL Long-chain acyl-CoA dehydrogenase; first step of beta-oxidation Downstream of CPT activity; knockout models show impaired fat oxidation
ACADM Medium-chain acyl-CoA dehydrogenase; beta-oxidation Related to fatty acid oxidation disorders; used as comparative model
HADHA Trifunctional protein subunit; beta-oxidation Mutations cause fatty acid oxidation defects; relevant to CPT pathway
HADHB Trifunctional protein subunit; beta-oxidation Similar to HADHA; used in metabolic studies
PPARA Peroxisome proliferator-activated receptor alpha; transcription factor regulating CPT1A expression Knockout models show reduced fatty acid oxidation
PPARGC1A PGC-1alpha; coactivator regulating mitochondrial biogenesis and CPT1 expression Overexpression models enhance fatty acid oxidation
PRKAA1 AMPK catalytic subunit alpha 1; phosphorylates and regulates CPT1 activity Knockout models show altered lipid metabolism
PRKAA2 AMPK catalytic subunit alpha 2; regulates CPT1 Tissue-specific roles in muscle and liver
MLYCD Malonyl-CoA decarboxylase; lowers malonyl-CoA and relieves CPT1 inhibition Overexpression reduces steatosis in models
ACACA Acetyl-CoA carboxylase alpha; produces malonyl-CoA, inhibits CPT1 Knockout models show increased fatty acid oxidation
ACACB Acetyl-CoA carboxylase beta; produces malonyl-CoA in muscle Regulates CPT1B activity
SREBF1 Sterol regulatory element-binding transcription factor 1; regulates lipogenic genes and malonyl-CoA production Overexpression models show increased steatosis
NR1H3 Liver X receptor alpha; regulates lipogenesis and CPT1 expression Knockout models show altered lipid metabolism

How Is carnitine O-palmitoyltransferase activity Regulated?

Carnitine O-palmitoyltransferase activity is regulated at multiple levels. Acute regulation occurs via malonyl-CoA, which inhibits CPT1A and CPT1B allosterically. Hormonal signals such as insulin suppress CPT1A expression, while glucagon and fasting induce it. AMPK phosphorylates and inhibits ACC, lowering malonyl-CoA and relieving CPT1 inhibition. Transcriptional regulation involves PPARalpha, PGC-1alpha, and SREBP-1, which modulate CPT1A and CPT1B expression in response to nutritional status. In hepatic stellate cells, CPT1A inhibition reduces fibrosis, suggesting cell-type-specific regulatory mechanisms.

carnitine O-palmitoyltransferase activity and Human Disease

GeneDisease / BiologyPotential Experimental Model
CPT1AObesity, hepatic steatosis, fibrosis, ovarian cancer stemnessLiver-specific knockout, overexpression, point mutation (malonyl-CoA binding site)
CPT1BCardiac and skeletal muscle fatty acid oxidation defectsMuscle-specific knockout, knock-in of human variant
CPT1CNeuronal metabolic regulation, cancerBrain-specific knockout, overexpression
CPT2CPT2 deficiency, rhabdomyolysis, cardiomyopathyKnockout, point mutation (catalytic residues), knock-in of patient mutations
SLC25A20CACT deficiency, hypoketotic hypoglycemiaKnockout, point mutation
Metabolic disorders and hepatic steatosis
Dysregulation of carnitine O-palmitoyltransferase activity contributes to obesity, insulin resistance, and non-alcoholic fatty liver disease. CPT1A activation by baicalin ameliorates diet-induced obesity and hepatic steatosis in mice. Conversely, CPT1A inhibition in hepatic stellate cells protects against fibrosis. These findings highlight the context-dependent role of CPT1A in metabolic disease.
Cancer stemness and ovarian cancer
CPT1A-mediated fatty acid oxidation supports cancer stem cell maintenance. In ovarian cancer stem cells, CPT1A-mediated succinylation of MFF promotes stemness, and CPT1A inhibition reduces tumorigenicity. This links carnitine O-palmitoyltransferase activity to cancer metabolism and suggests CPT1A as a therapeutic target.
Liver fibrosis and ferroptosis
Activated hepatic stellate cells rely on CPT1A for energy. Inhibition of CPT1A or targeting it with rubimaillin triggers ferroptosis in activated hepatic stellate cells and ameliorates liver fibrosis. This demonstrates that carnitine O-palmitoyltransferase activity can be exploited to induce ferroptosis in fibrogenic cells.
Inherited carnitine palmitoyltransferase deficiencies
Mutations in CPT1A and CPT2 cause inherited disorders characterized by impaired long-chain fatty acid oxidation, hypoketotic hypoglycemia, and cardiomyopathy. These rare diseases underscore the essential role of carnitine O-palmitoyltransferase activity in human energy metabolism.

From carnitine O-palmitoyltransferase activity-Related Genes to Experimental Models

Research QuestionSuitable Model
Does CPT1A loss reduce hepatic steatosis?Liver-specific CPT1A knockout mouse or CRISPR knockout HepG2 cells
Does CPT1A inhibition protect against fibrosis?Hepatic stellate cell-specific CPT1A knockout or pharmacological inhibition
Does CPT1A-mediated succinylation regulate cancer stemness?CPT1A knockout ovarian cancer cells, point mutation of succinylation site
What is the effect of CPT1A activation on obesity?Overexpression of CPT1A in liver or treatment with baicalin in diet-induced obese mice
How do CPT2 mutations affect enzyme activity?Knock-in of patient mutations in cell lines, enzymatic assays
Does malonyl-CoA binding regulate CPT1A?Point mutations in malonyl-CoA binding site, knock-in models

How to Study the carnitine O-palmitoyltransferase activity Process

MethodWhat It MeasuresTypical Application
Radiolabeled substrate assayEnzyme activity (palmitoylcarnitine formation)Kinetic characterization, inhibitor screening
CRISPR knockout screenGene essentiality and modifiers of CPT activityIdentify synthetic lethal partners in cancer
Metabolomics (LC-MS)Acylcarnitine and CoA levelsAssess metabolic flux in KO or overexpression models
LipidomicsFatty acid composition and lipid speciesEvaluate steatosis and membrane changes
ChemoproteomicsTarget engagement of small moleculesDrug discovery for CPT1 activators/inhibitors
Western blotProtein expression and post-translational modificationsValidate KO, overexpression, or succinylation
Seahorse assayOxygen consumption rate (fatty acid oxidation)Measure mitochondrial function in live cells
ImmunofluorescenceSubcellular localization of CPT1/CPT2Confirm mitochondrial targeting
Enzymatic activity assays
Carnitine O-palmitoyltransferase activity can be measured using radiolabeled substrates or coupled assays that detect CoA release. These assays are used to determine kinetic parameters, isoform specificity, and the effects of inhibitors such as malonyl-CoA.
CRISPR-based genetic screens
Genome-wide CRISPR knockout screens can identify genes that modulate carnitine O-palmitoyltransferase activity or its downstream effects. Such screens have revealed regulators of fatty acid oxidation and CPT1A dependency in cancer cells.
Metabolomics and lipidomics
Mass spectrometry-based metabolomics and lipidomics quantify acylcarnitines, fatty acids, and intermediates of beta-oxidation. These methods are essential to assess the impact of CPT1/CPT2 perturbations on cellular metabolism.
Proteomics and chemoproteomics
Chemoproteomics using activity-based probes can identify small molecules that activate or inhibit CPT1. For example, baicalin was identified as a CPT1 activator through chemoproteomics. Proteomics can also reveal post-translational modifications such as succinylation.

How CRISPR Can Be Used to Study GO:0004095 carnitine O-palmitoyltransferase activity

Knockout

CRISPR knockout of CPT1A, CPT1B, CPT1C, or CPT2 enables loss-of-function studies to determine their roles in fatty acid oxidation, cell survival, and disease. For example, CPT1A knockout in ovarian cancer cells reduces stemness and tumor growth. Liver-specific CPT1A knockout protects against steatosis and fibrosis.

Point Mutation

Point mutations can be introduced to dissect catalytic residues, malonyl-CoA binding sites, or post-translational modification sites. For instance, mutation of the succinylation site on MFF or CPT1A can reveal its role in cancer stemness. Point mutations in CPT2 can model patient-derived deficiencies.

Knock-in

Knock-in of disease-associated mutations or tagged versions of CPT1/CPT2 allows precise modeling of human variants and tracking of protein localization. This is particularly useful for studying CPT2 deficiency mutations.

Overexpression

Overexpression of CPT1A or CPT1B via CRISPR activation or lentiviral delivery can enhance fatty acid oxidation and reduce steatosis. For example, hepatic CPT1A overexpression ameliorates diet-induced obesity. Overexpression models are also used to study downstream signaling.

How EDITGENE Supports carnitine O-palmitoyltransferase activity Research

Researchers studying carnitine O-palmitoyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in fatty acid oxidation, metabolic disease, or cancer. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of CPT1/CPT2 and related genes.
Contact EDITGENE today to design your custom CRISPR model for carnitine O-palmitoyltransferase activity research.

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Frequently Asked Questions About carnitine O-palmitoyltransferase activity

Carnitine O-palmitoyltransferase activity (GO:0004095) is the enzymatic activity that transfers a palmitoyl group from palmitoyl-CoA to L-carnitine, forming L-palmitoylcarnitine and CoA. It is essential for mitochondrial long-chain fatty acid oxidation.
The main genes are CPT1A, CPT1B, CPT1C, and CPT2, which encode different isoforms of the enzyme. SLC25A20 encodes the transporter that works with CPT1/CPT2 in the carnitine shuttle.
CPT1A is the liver-type isoform of carnitine palmitoyltransferase 1. It catalyzes the rate-limiting step of mitochondrial fatty acid oxidation and is inhibited by malonyl-CoA. It is a target in obesity, steatosis, fibrosis, and cancer.
It is regulated by malonyl-CoA inhibition, hormonal signals (insulin, glucagon), AMPK, and transcription factors such as PPARalpha and PGC-1alpha.
Mutations in CPT1A and CPT2 cause inherited disorders with hypoketotic hypoglycemia, cardiomyopathy, and rhabdomyolysis. CPT1A dysregulation is also linked to obesity, fatty liver, and fibrosis.
Carnitine supplementation may influence muscle bioenergetics by providing substrate for the carnitine shuttle, but its effects on enzyme activity are context-dependent.
CPT1A supports fatty acid oxidation in cancer cells and cancer stem cells. In ovarian cancer stem cells, CPT1A-mediated succinylation of MFF promotes stemness, and CPT1A inhibition reduces tumorigenicity.
Common methods include enzymatic activity assays, CRISPR knockout/overexpression models, metabolomics, lipidomics, and chemoproteomics.
CPT1 is located on the outer mitochondrial membrane and catalyzes the formation of acylcarnitines; CPT2 is on the inner membrane and catalyzes the reverse reaction to regenerate acyl-CoA inside the matrix.
Yes, CPT1A is a target for metabolic diseases and fibrosis. Activators like baicalin ameliorate steatosis, while inhibitors can reduce fibrosis by inducing ferroptosis in hepatic stellate cells.

Conclusion

Carnitine O-palmitoyltransferase activity (GO:0004095) is a fundamental molecular function that controls mitochondrial long-chain fatty acid oxidation. Its dysregulation is implicated in metabolic disorders, fibrosis, and cancer, making it a high-value target for therapeutic intervention. Advances in CRISPR-based models and multi-omics approaches are accelerating our understanding of isoform-specific functions and regulatory mechanisms. EDITGENE provides end-to-end solutions to generate and characterize these models, empowering researchers to translate discoveries into clinical applications.

References

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  2. 2. Fondevila MF et al.. 2022. Inhibition of carnitine palmitoyltransferase 1A in hepatic stellate cells protects against fibrosis.. J Hepatol 77(1):15-28 PMID: 35167910
  3. 3. Gnoni A et al.. 2020. Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise?. Molecules 25(1) PMID: 31906370
  4. 4. Bonnefont JP et al.. 1999. Carnitine palmitoyltransferase deficiencies.. Mol Genet Metab 68(4):424-40 PMID: 10607472
  5. 5. Dai J et al.. 2018. Chemoproteomics reveals baicalin activates hepatic CPT1 to ameliorate diet-induced obesity and hepatic steatosis.. Proc Natl Acad Sci U S A 115(26):E5896-E5905 PMID: 29891721
  6. 6. Zhu Y et al.. 2025. CPT1A-mediated MFF succinylation promotes stemness maintenance in ovarian cancer stem cells.. Commun Biol 8(1):250 PMID: 39956875
  7. 7. Bremer J. 1983. Carnitine--metabolism and functions.. Physiol Rev 63(4):1420-80 PMID: 6361812
  8. 8. Zhang D et al.. 2026. Rubimaillin ameliorates liver fibrosis by triggering the ferroptosis of activated hepatic stellate cells through targeting CPT1A.. Int J Biol Sci 22(4):2065-2084 PMID: 41694586
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