GO:0033819 lipoyl(octanoyl) transferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0033819 (lipoyl(octanoyl) transferase activity) catalyzes the transfer of an octanoyl group from octanoyl-[ACP] to a specific lysine residue on a target protein, producing N6-octanoyl-L-lysyl-[protein] and holo-[ACP].
• In Escherichia coli, the lipB gene encodes the lipoyl(octanoyl) transferase that performs this reaction on the H protein of the glycine cleavage system and on E2 subunits of 2-oxoacid dehydrogenase complexes.
• The enzyme is the first step in the de novo lipoylation pathway; the octanoyl group is subsequently converted to a lipoyl group by lipoate synthase (LipA).
• In humans, the orthologous enzyme LIPT2 transfers octanoyl groups to the H protein of the glycine cleavage system and to E2 subunits of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase.
• Biallelic mutations in LIPT2 cause a severe neonatal encephalopathy with mitochondrial lipoylation defects, highlighting the clinical importance of this activity.
• LIPT2 mis-targeting or degradation leads to mitochondrial dysfunction and apoptosis, and has been linked to neurodegeneration such as Huntington's disease [1,5].
Description
Lipoyl(octanoyl) transferase activity (GO:0033819) is a molecular function that attaches an eight-carbon octanoyl chain to specific lysine residues of target proteins, using octanoyl-[acyl-carrier-protein] (octanoyl-[ACP]) as the donor. This reaction is the committed step in the de novo lipoylation pathway and is essential for the function of several multienzyme complexes that are central to energy metabolism and amino acid catabolism. The enzyme is conserved from bacteria to humans, and its bacterial prototype is encoded by the lipB gene in Escherichia coli. In humans, the orthologous enzyme LIPT2 performs the same reaction in mitochondria, and its dysfunction has been linked to severe metabolic and neurological disorders. Because lipoylation is indispensable for the activity of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, and the glycine cleavage system, understanding GO:0033819 is fundamental to mitochondrial biology and to the study of inborn errors of metabolism. The reaction also represents a promising target for antimicrobial and antiparasitic drug development, as lipoylation enzymes are absent in some pathogens or differ structurally from their human counterparts [6,7].
lipoyl(octanoyl) transferase activity At A Glance
| GO ID | GO:0033819 |
|---|---|
| GO term | lipoyl(octanoyl) transferase activity |
| Ontology | molecular_function |
| Synonym | lipoate/octanoate transferase activity; lipoyl (octanoyl)-acyl-carrier-protein-protein N-lipoyltransferase activity; octanoyl-acyl-carrier-protein:protein N-octanoyltransferase activity; octanoyl transferase activity (acting on glycine-cleavage complex H protein) |
| Major function | Transfer of an octanoyl group from octanoyl-[ACP] to a specific lysine residue on target proteins, forming an octanoylated protein intermediate in the de novo lipoylation pathway |
| Reaction | L-lysyl-[protein] + octanoyl-[ACP] = H+ + holo-[ACP] + N6-octanoyl-L-lysyl-[protein] |
| Substrates | L-lysyl-[protein] (e.g., H protein of glycine cleavage system, E2 subunits of 2-oxoacid dehydrogenases) and octanoyl-[ACP] |
| Products | N6-octanoyl-L-lysyl-[protein], holo-[ACP], H+ |
| Cofactors | None known; the reaction does not require a cofactor |
| Localization | Mitochondrial matrix in eukaryotes; cytoplasm in bacteria |
What Is GO:0033819?
GO:0033819, lipoyl(octanoyl) transferase activity, is defined as the catalysis of the reaction: L-lysyl-[protein] + octanoyl-[ACP] = H+ + holo-[ACP] + N6-octanoyl-L-lysyl-[protein]. In other words, the enzyme transfers an octanoyl group from octanoyl-acyl carrier protein to a lysine residue on a target protein, releasing the free acyl carrier protein (holo-ACP) and forming an octanoylated protein intermediate. This activity is the first step in the biosynthesis of lipoic acid-dependent enzymes; the octanoyl moiety is later converted to a lipoyl group by the action of lipoate synthase.
Why Is lipoyl(octanoyl) transferase activity Important in Cell Biology?
GO:0033819 is essential for the post-translational modification of key metabolic enzymes, and its dysfunction leads to severe human disease. The reaction it catalyzes is the first committed step in the de novo lipoylation pathway, which is required for the activity of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, and the glycine cleavage system. In humans, mutations in LIPT2, the enzyme responsible for this activity, cause a mitochondrial lipoylation defect associated with severe neonatal encephalopathy, often leading to death in early infancy. Moreover, mis-targeting or degradation of LIPT2 results in mitochondrial dysfunction and apoptosis, and has been implicated in neurodegenerative conditions such as Huntington's disease [1,5]. Therefore, understanding the molecular mechanism, regulation, and disease relevance of GO:0033819 is critical for developing therapeutic strategies for metabolic and neurodegenerative disorders.
• Essential for the de novo lipoylation of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, and the glycine cleavage system.
• Mutations in human LIPT2 cause severe neonatal encephalopathy with mitochondrial lipoylation defects.
• Mis-targeting of LIPT2 triggers apoptotic cell death, linking the enzyme to neurodegeneration.
• LIPT2 degradation by NEDD4L contributes to mitochondrial dysfunction in Huntington's disease.
• The enzyme is a potential target for antimicrobials because lipoylation is essential in bacteria and some parasites [6,7].
• Apicomplexan parasites possess a single lipoic acid synthase, making the pathway a possible drug target.
• The reaction is conserved across archaea, bacteria, and eukaryotes, facilitating comparative studies.
• Defects in lipoylation are associated with metabolic disorders and mitochondrial diseases.
• The enzyme provides a model system for studying protein-protein interactions and substrate recognition.
• Research on GO:0033819 informs the design of CRISPR models for metabolic and neurodegenerative diseases [1,4].
Molecular Mechanism of lipoyl(octanoyl) transferase activity
Substrate recognition and binding
In simple terms: The enzyme first grabs the octanoyl carrier and the target protein.
The lipoyl(octanoyl) transferase recognizes and binds octanoyl-[ACP] and the target protein, such as the H protein of the glycine cleavage system or the E2 subunit of 2-oxoacid dehydrogenases. In E. coli, the enzyme is encoded by lipB and specifically interacts with the apo form of these proteins. The binding likely involves a conserved active site that positions the octanoyl group for transfer to a specific lysine residue.
Catalytic transfer of the octanoyl group
In simple terms: The enzyme moves the octanoyl chain onto a lysine on the target protein.
The enzyme catalyzes the transfer of the octanoyl moiety from octanoyl-[ACP] to the epsilon-amino group of a conserved lysine residue on the target protein, forming an amide bond and releasing holo-[ACP]. This reaction is the defining activity of GO:0033819 and produces N6-octanoyl-L-lysyl-[protein]. The mechanism is thought to proceed via a ping-pong or sequential mechanism, although detailed kinetic studies are limited.
Conversion to lipoyl group
In simple terms: Another enzyme later turns the octanoyl chain into a lipoyl chain.
The octanoylated protein is subsequently converted to a lipoylated protein by the action of lipoate synthase (LipA in bacteria, LIAS in humans), which inserts sulfur atoms into the octanoyl chain to form the lipoyl group. This two-step pathway is the de novo lipoylation route, and GO:0033819 provides the octanoyl intermediate.
Structural features of the enzyme
In simple terms: The enzyme has a specific shape that lets it do its job.
The E. coli lipoyl(octanoyl) transferase has been expressed, purified, and physically characterized, revealing a monomeric or dimeric structure with an alpha/beta fold. Structural studies of archaeal lipoylation complexes have provided insights into how the enzyme interacts with its substrates and partner proteins. The active site contains conserved residues that are essential for catalysis, although the exact catalytic residues are still being investigated.
Regulation and post-translational control
In simple terms: The amount of this enzyme can be controlled by degradation or mis-targeting.
In humans, LIPT2 levels are regulated by proteasomal degradation; the E3 ubiquitin ligase NEDD4L promotes LIPT2 degradation, leading to mitochondrial dysfunction in Huntington's disease models. Additionally, mis-targeting of LIPT2 away from mitochondria induces apoptotic cell death, indicating that proper subcellular localization is critical for its function. These findings suggest that GO:0033819 activity is tightly regulated at the protein level.
Key Genes Involved in GO:0033819 lipoyl(octanoyl) transferase activity
The following genes and proteins are directly involved in or regulate lipoyl(octanoyl) transferase activity (GO:0033819) and its associated pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LIPT2 | Human lipoyl(octanoyl) transferase; transfers octanoyl to H protein and E2 subunits | Mutations cause neonatal encephalopathy; degradation linked to Huntington's disease [1,4] |
| LIPB | E. coli lipoyl(octanoyl) transferase; encoded by lipB gene | Model enzyme for mechanistic and structural studies [2,3] |
| LIAS | Lipoate synthase; converts octanoylated proteins to lipoylated proteins | Second step in de novo lipoylation; mutations cause lipoic acid deficiency |
| GCSH | H protein of glycine cleavage system; substrate for lipoylation | Defects cause glycine encephalopathy; target of LIPT2 |
| PDHX | E3-binding protein of pyruvate dehydrogenase complex; substrate for lipoylation | Lipoylation required for PDH activity; defects cause lactic acidosis |
| DLD | Dihydrolipoamide dehydrogenase; component of 2-oxoacid dehydrogenase complexes | Lipoylation of E2 subunits affects DLD function |
| DLST | Dihydrolipoamide succinyltransferase; E2 subunit of 2-oxoglutarate dehydrogenase | Lipoylation essential for TCA cycle |
| NEDD4L | E3 ubiquitin ligase; promotes LIPT2 degradation | Linked to mitochondrial dysfunction in Huntington's disease |
| LIPT1 | Lipoyltransferase; transfers lipoate to target proteins in salvage pathway | Mutations cause lipoylation defects and metabolic disease |
| ACACA | Acetyl-CoA carboxylase; provides malonyl-CoA for fatty acid synthesis | Indirectly affects octanoyl-ACP availability |
| ACP | Acyl carrier protein; carries octanoyl group | Direct substrate for LIPT2/LipB |
| PDHA1 | Pyruvate dehydrogenase E1 alpha subunit | Lipoylation of PDH complex affects its activity |
| OGDH | 2-oxoglutarate dehydrogenase E1 subunit | Lipoylation of OGDH complex required for TCA cycle |
| GCSH | Glycine cleavage system H protein | Lipoylation essential for glycine metabolism |
| LIAS | Lipoic acid synthase | Converts octanoyl to lipoyl; mutations cause hyperglycinemia |
| BOLA3 | Iron-sulfur cluster assembly protein | Required for LIAS function; mutations cause lipoylation defects |
| NFU1 | Iron-sulfur cluster scaffold protein | Required for LIAS function; mutations cause lipoylation defects |
| IBA57 | Iron-sulfur cluster assembly protein | Required for LIAS function; mutations cause lipoylation defects |
How Is lipoyl(octanoyl) transferase activity Regulated?
The activity of lipoyl(octanoyl) transferase is primarily regulated at the level of protein stability and localization. In human cells, LIPT2 is targeted for proteasomal degradation by the E3 ubiquitin ligase NEDD4L, and this degradation leads to mitochondrial dysfunction and neurodegeneration in Huntington's disease models. Additionally, mis-targeting of LIPT2 away from mitochondria results in apoptotic cell death, indicating that correct subcellular localization is essential for its function. The expression of the bacterial enzyme LipB is likely regulated in response to metabolic demand, although specific transcription factors have not been fully characterized. Overall, regulation occurs through post-translational mechanisms and protein-protein interactions rather than through direct allosteric control [1,5].
lipoyl(octanoyl) transferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| LIPT2 | Severe neonatal encephalopathy with mitochondrial lipoylation defect | Patient-derived fibroblasts; LIPT2 knockout cell lines; knock-in of patient mutations |
| LIPT2 | Huntington's disease; NEDD4L-mediated degradation | LIPT2 overexpression in HD cell models; NEDD4L knockout |
| LIPT2 | Apoptosis due to mis-targeting | LIPT2 mutants with altered localization; live-cell imaging |
| LIAS | Lipoic acid deficiency and hyperglycinemia | LIAS knockout models; lipoylation assays |
| BOLA3 | Multiple mitochondrial dysfunctions syndrome | BOLA3 knockout cells; rescue with lipoate |
LIPT2 mutations and severe neonatal encephalopathy
Biallelic mutations in LIPT2, the human gene encoding lipoyl(octanoyl) transferase, cause a mitochondrial lipoylation defect associated with severe neonatal encephalopathy. Affected infants present with early-onset seizures, hypotonia, and lactic acidosis, and often die in infancy. The mutations lead to reduced lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase, impairing energy metabolism.
LIPT2 in neurodegeneration and Huntington's disease
LIPT2 degradation induced by NEDD4L contributes to mitochondrial dysfunction and neurodegeneration in Huntington's disease. In cellular and animal models, increased NEDD4L activity leads to LIPT2 ubiquitination and degradation, resulting in impaired mitochondrial respiration and increased oxidative stress. This suggests that stabilizing LIPT2 could be a therapeutic strategy for Huntington's disease.
Apoptosis and mis-targeting of LIPT2
Mis-targeting of LIPT2 away from mitochondria triggers apoptotic cell death, highlighting the importance of proper localization for cellular survival. This finding links defects in lipoylation to programmed cell death pathways and suggests that LIPT2 mis-localization may contribute to degenerative diseases.
Parasitic infections and drug targeting
Apicomplexan parasites such as Toxoplasma gondii and Plasmodium falciparum contain a single lipoic acid synthase located in the plastid, making the lipoylation pathway a potential target for antiparasitic drugs. Inhibiting lipoyl(octanoyl) transferase activity could disrupt parasite metabolism and provide a novel therapeutic approach.
From lipoyl(octanoyl) transferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of LIPT2 loss on mitochondrial function? | LIPT2 knockout cell lines (e.g., HEK293T, HeLa) |
| How do patient mutations affect enzyme activity? | Knock-in of specific LIPT2 mutations (e.g., c.89T>C) in cell lines |
| Does LIPT2 degradation contribute to neurodegeneration? | Overexpression of NEDD4L in neuronal cells; LIPT2 overexpression |
| What is the role of LIPT2 in apoptosis? | LIPT2 mis-targeting mutants; flow cytometry for apoptosis |
| Can lipoylation be restored by lipoic acid supplementation? | LIPT2 knockout cells treated with lipoic acid; Western blot for lipoylated proteins |
| How does LipB recognize its substrates? | Recombinant E. coli LipB; site-directed mutagenesis; crystallography [2,3] |
How to Study the lipoyl(octanoyl) transferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro enzymatic assay | Transfer of octanoyl group to protein substrate | Kinetic characterization of LIPT2/LipB [2,3] |
| Western blot with anti-lipoic acid | Levels of lipoylated proteins | Assessment of lipoylation defects in patient cells |
| Mass spectrometry | Identification of octanoylated lysine residues | Mapping modification sites on target proteins |
| CRISPR-Cas9 knockout | Loss-of-function phenotype | Studying the role of LIPT2 in mitochondrial function |
| CRISPR-Cas9 knock-in | Effect of specific mutations | Modeling patient mutations in cell lines |
| Co-immunoprecipitation | Protein-protein interactions | Identifying components of lipoylation machinery |
| Live-cell imaging | Subcellular localization of LIPT2 | Investigating mis-targeting and apoptosis |
| RNA-seq | Transcriptional changes upon LIPT2 perturbation | Identifying compensatory pathways |
Enzymatic assays for lipoyl(octanoyl) transferase activity
The activity of GO:0033819 can be measured in vitro using recombinant enzyme and substrates. A typical assay monitors the transfer of octanoyl group from octanoyl-[ACP] to a protein substrate, such as the H protein, using radioactive or fluorescent labeling [2,3]. Alternatively, mass spectrometry can detect the formation of N6-octanoyl-L-lysyl-[protein].
Western blotting for lipoylation
Lipoylation of target proteins can be assessed by Western blot using anti-lipoic acid antibodies. This method is widely used to evaluate the impact of LIPT2 mutations or knockdown on the lipoylation status of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. It provides a semi-quantitative measure of pathway activity.
CRISPR-Cas9 knockout and knock-in models
CRISPR-Cas9 can be used to generate LIPT2 knockout cell lines to study loss of function, or to introduce patient-specific mutations via homology-directed repair. These models are valuable for understanding disease mechanisms and for testing therapeutic interventions [1,4].
Proteomics and interactomics
Affinity purification coupled with mass spectrometry can identify proteins interacting with LIPT2 or LipB, revealing the composition of lipoylation complexes. Quantitative proteomics can also measure changes in lipoylation status across the proteome in response to genetic or pharmacological perturbations.
How CRISPR Can Be Used to Study GO:0033819 lipoyl(octanoyl) transferase activity
Knockout
CRISPR-Cas9 knockout of LIPT2 in human cell lines results in loss of lipoyl(octanoyl) transferase activity, leading to decreased lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase, and impaired mitochondrial respiration. These models are useful for studying the metabolic consequences of LIPT2 deficiency and for testing rescue strategies such as lipoic acid supplementation.
Point Mutation
Knock-in of patient-specific point mutations in LIPT2 (e.g., c.89T>C) using CRISPR-Cas9 and homology-directed repair allows researchers to study the functional impact of these mutations in a controlled cellular context. Such models can reveal whether a mutation affects enzyme stability, localization, or catalytic activity.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) into the endogenous LIPT2 locus enables precise tracking of protein expression, localization, and interactions without overexpression artifacts. Tagged knock-in models are valuable for studying LIPT2 degradation by NEDD4L and for proteomic analyses.
Overexpression
Overexpression of LIPT2 or its bacterial homolog LipB can be used to study gain-of-function effects, such as increased lipoylation and enhanced mitochondrial function. Conversely, overexpression of NEDD4L leads to LIPT2 degradation, providing a model for neurodegeneration.
How EDITGENE Supports lipoyl(octanoyl) transferase activity Research
Researchers studying lipoyl(octanoyl) transferase activity-related genes often need to determine whether a candidate gene is causally involved in mitochondrial metabolism, lipoylation, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this research, from gene knockout to precise point mutations and library screening.
Contact EDITGENE today to design your custom CRISPR model for lipoyl(octanoyl) transferase activity research.
Frequently Asked Questions About lipoyl(octanoyl) transferase activity
What is lipoyl(octanoyl) transferase activity?
It is a molecular function (GO:0033819) that transfers an octanoyl group from octanoyl-[ACP] to a lysine residue on a target protein, forming an octanoylated protein intermediate in the de novo lipoylation pathway.
What genes are involved in lipoyl(octanoyl) transferase activity?
The main genes are LIPT2 in humans and lipB in E. coli, which encode the enzyme that catalyzes this reaction [3,4].
What is the reaction catalyzed by GO:0033819?
The reaction is: L-lysyl-[protein] + octanoyl-[ACP] = H+ + holo-[ACP] + N6-octanoyl-L-lysyl-[protein].
What diseases are associated with LIPT2 mutations?
Biallelic mutations in LIPT2 cause severe neonatal encephalopathy with mitochondrial lipoylation defects, and LIPT2 degradation has been linked to Huntington's disease [1,4].
How is lipoyl(octanoyl) transferase activity regulated?
It is regulated by protein stability and localization; NEDD4L promotes LIPT2 degradation, and mis-targeting leads to apoptosis [1,5].
What are the substrates of lipoyl(octanoyl) transferase?
The substrates are octanoyl-[ACP] and target proteins such as the H protein of the glycine cleavage system and E2 subunits of 2-oxoacid dehydrogenases.
What is the difference between LIPT2 and LIPT1?
LIPT2 transfers octanoyl groups in the de novo pathway, while LIPT1 transfers lipoyl groups in the salvage pathway.
How can I study lipoyl(octanoyl) transferase activity in the lab?
You can use in vitro enzymatic assays, Western blotting for lipoylation, and CRISPR knockout or knock-in models [2,3,4].
Is lipoyl(octanoyl) transferase a drug target?
Yes, it is a potential target for antimicrobials and antiparasitic drugs because lipoylation is essential in bacteria and some parasites [6,7].
What model organisms are used to study GO:0033819?
E. coli is a common model for the bacterial enzyme, while human cell lines and mouse models are used for LIPT2 studies [2,3,4].
Conclusion
GO:0033819, lipoyl(octanoyl) transferase activity, is a fundamental molecular function that initiates the de novo lipoylation of key metabolic enzymes. Its importance is underscored by severe human diseases caused by mutations in LIPT2, including neonatal encephalopathy and neurodegeneration [1,4]. The enzyme is also a promising target for antimicrobial and antiparasitic therapies [6,7]. Continued research using CRISPR-based models and advanced biochemical assays will further elucidate its mechanism and regulation, potentially leading to new therapeutic strategies.
References
- 1. Fan P et al.. 2025. NEDD4L induces mitochondrial dysfunction and neurodegeneration by promoting LIPT2 degradation in Huntington's disease.. Proc Natl Acad Sci U S A 122(29):e2503342122 PMID: 40663606
- 2. Nesbitt NM et al.. 2005. Expression, purification, and physical characterization of Escherichia coli lipoyl(octanoyl)transferase.. Protein Expr Purif 39(2):269-82 PMID: 15642479
- 3. Jordan SW et al.. 2003. The Escherichia coli lipB gene encodes lipoyl (octanoyl)-acyl carrier protein:protein transferase.. J Bacteriol 185(5):1582-9 PMID: 12591875
- 4. Habarou F et al.. 2017. Biallelic Mutations in LIPT2 Cause a Mitochondrial Lipoylation Defect Associated with Severe Neonatal Encephalopathy.. Am J Hum Genet 101(2):283-290 PMID: 28757203
- 5. Bernardinelli E et al.. 2017. Mis-targeting of the mitochondrial protein LIPT2 leads to apoptotic cell death.. PLoS One 12(6):e0179591 PMID: 28628643
- 6. Posner MG et al.. 2013. Post-translational modification in the archaea: structural characterization of multi-enzyme complex lipoylation.. Biochem J 449(2):415-25 PMID: 23116157
- 7. Thomsen-Zieger N et al.. 2003. Apicomplexan parasites contain a single lipoic acid synthase located in the plastid.. FEBS Lett 547(1-3):80-6 PMID: 12860390
