GO:0016885 ligase activity, forming carbon-carbon bonds: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016885 describes the molecular function of joining two molecules via a carbon-carbon bond, coupled to the hydrolysis of ATP or a similar triphosphate.
• This activity is central to biotin activation, where biotin protein ligase (BirA) adenylates biotin to form the reactive intermediate biotinyl-5'-AMP.
• The catalytic mechanism involves nucleophilic attack and formation of a carbon-carbon bond, as illustrated by computational studies of enzymatic CO2 fixation.
• Biotin protein ligase from Pyrococcus horikoshii OT3 provides high-resolution structural snapshots of the adenylation step, revealing the active-site architecture.
• Dysregulation of carbon-carbon bond-forming ligases can impact metabolic pathways and has been linked to disease states, though direct human disease associations remain an active area of research.
• CRISPR-based knockout, point-mutation, and knock-in models are powerful tools to dissect the physiological roles of these ligases.
Description
Ligase activity, forming carbon-carbon bonds (GO:0016885) is a fundamental molecular function that enables the construction of carbon-carbon bonds, a cornerstone of biosynthesis and metabolism. This activity is defined by the catalysis of joining two molecules via a carbon-carbon bond, with the concomitant hydrolysis of the diphosphate bond in ATP or a similar triphosphate. Unlike many ligases that form carbon-heteroatom bonds, this class of enzymes directly forges the carbon skeleton, making it essential for processes such as biotin activation and carbon dioxide fixation. Researchers study GO:0016885 to understand how cells build complex molecules, how energy from ATP is harnessed for bond formation, and how defects in these enzymes contribute to metabolic disorders and disease. The availability of structural and computational data, such as the crystal structures of biotin protein ligase and quantum chemical analyses of enzymatic CO2 fixation, provides a mechanistic framework for investigating this activity.
ligase activity, forming carbon-carbon bonds At A Glance
| GO ID | GO:0016885 |
|---|---|
| GO term | ligase activity, forming carbon-carbon bonds |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Catalysis of carbon-carbon bond formation coupled to ATP hydrolysis |
| EC number | 6.3.-.- (ligases forming carbon-carbon bonds) |
| Representative enzyme | Biotin protein ligase (BirA) |
| Cofactor requirement | ATP or similar triphosphate |
| Subcellular location | Cytoplasm, mitochondria (varies by enzyme) |
What Is GO:0016885?
According to the Gene Ontology, GO:0016885 (ligase activity, forming carbon-carbon bonds) is defined as the catalysis of the joining of two molecules via a carbon-carbon bond, with the concomitant hydrolysis of the diphosphate bond in ATP or a similar triphosphate. In other words, it is an ATP-dependent ligase reaction that creates a new C-C bond between two substrates, using the energy released from ATP hydrolysis to drive the condensation.
Why Is ligase activity, forming carbon-carbon bonds Important in Cell Biology?
GO:0016885 is important because carbon-carbon bond formation is a rate-limiting step in many biosynthetic pathways, including fatty acid synthesis, biotin metabolism, and carbon fixation. Understanding this activity at the molecular level informs efforts in metabolic engineering, drug discovery, and the development of biocatalysts. Moreover, mutations in genes encoding such ligases can disrupt cellular metabolism and have been implicated in disease, making them potential therapeutic targets.
• Enables the biosynthesis of essential metabolites such as biotin, which is a cofactor for carboxylases.
• Plays a key role in carbon fixation pathways, contributing to global carbon cycling.
• Provides a paradigm for studying ATP-dependent bond formation and energy coupling.
• Mutations in carbon-carbon bond-forming ligases can lead to metabolic disorders.
• Serves as a target for antibiotics and herbicides due to its essentiality in microorganisms and plants.
• Facilitates the production of biofuels and industrial chemicals through engineered pathways.
• Offers insights into enzyme evolution and catalytic promiscuity.
• Enables the design of novel biocatalysts for synthetic chemistry.
Molecular Mechanism of ligase activity, forming carbon-carbon bonds
Substrate Binding and Activation
In simple terms: The enzyme grabs its substrates and uses ATP to prime one of them for bond formation.
The reaction begins with the binding of two substrate molecules and a molecule of ATP (or a similar triphosphate) to the enzyme's active site. In the case of biotin protein ligase, the enzyme binds biotin and ATP, and catalyzes the adenylation of biotin to form biotinyl-5'-AMP, a reactive intermediate. This step activates the carboxyl group of biotin, making it susceptible to nucleophilic attack. Structural studies of biotin protein ligase from Pyrococcus horikoshii OT3 have revealed the precise arrangement of residues that coordinate ATP and biotin, providing a structural basis for this activation.
Carbon-Carbon Bond Formation
In simple terms: The activated molecule attacks another molecule, forming a new carbon-carbon bond.
Following activation, the enzyme facilitates the attack of a nucleophilic carbon on the electrophilic carbon of the activated substrate, leading to the formation of a new carbon-carbon bond. In biotin protein ligase, the activated biotinyl-5'-AMP is transferred to a specific lysine residue of the acceptor protein (e.g., acetyl-CoA carboxylase), forming a biotinyl-lysine amide bond; however, this is a carbon-heteroatom bond. For true carbon-carbon bond-forming ligases, such as those involved in CO2 fixation, the mechanism involves the direct coupling of two carbon-containing species. Computational studies using atom-condensed Fukui functions have shed light on the electronic reorganization during enzymatic CO2 fixation, highlighting the role of active-site residues in stabilizing the transition state.
ATP Hydrolysis and Product Release
In simple terms: ATP is split to provide energy, and the product is released.
The formation of the carbon-carbon bond is coupled to the hydrolysis of ATP to AMP and pyrophosphate (or ADP and phosphate, depending on the enzyme). This hydrolysis provides the thermodynamic driving force for the ligation reaction. In biotin protein ligase, the adenylation step consumes ATP and releases pyrophosphate, and the subsequent transfer step releases AMP. The energy from ATP hydrolysis ensures that the reaction proceeds forward despite the otherwise unfavorable condensation. After bond formation, the product is released from the active site, and the enzyme is ready for another cycle.
Structural Determinants of Catalysis
In simple terms: The enzyme's three-dimensional shape positions the substrates perfectly for reaction.
High-resolution crystal structures of biotin protein ligase from Pyrococcus horikoshii OT3 in complex with biotin and ATP analogues have revealed a conserved active site with a Rossmann-like fold that binds the nucleotide. Key residues, including a conserved lysine and arginine, stabilize the phosphate groups of ATP and the carboxylate of biotin. The structures also show a flexible loop that closes over the active site upon substrate binding, excluding water and preventing premature hydrolysis of the intermediate. These structural insights are critical for understanding how carbon-carbon bond-forming ligases achieve substrate specificity and catalysis.
Cofactors and Metal Requirements
In simple terms: Some of these enzymes need metal ions or other helpers to work.
While many carbon-carbon bond-forming ligases, such as biotin protein ligase, do not require metal ions for catalysis, others may depend on divalent cations like Mg2+ to coordinate ATP and stabilize the transition state. For example, the enzymatic fixation of CO2 often involves metal centers that activate CO2 or stabilize the carboxylate product. The specific cofactor requirements vary widely among enzymes in this GO class, reflecting the diversity of chemical strategies for forging C-C bonds. Researchers should consult individual enzyme studies for precise cofactor dependencies.
Key Genes Involved in GO:0016885 ligase activity, forming carbon-carbon bonds
The following genes encode enzymes and proteins that exhibit or are directly associated with ligase activity forming carbon-carbon bonds (GO:0016885), based on published biochemical and structural studies.
| Gene | Major Role | Research Relevance |
|---|---|---|
| birA | Biotin protein ligase; activates biotin to biotinyl-5'-AMP | Model enzyme for GO:0016885; structural studies reveal adenylation mechanism |
| accB | Biotin carboxyl carrier protein; acceptor for biotinylation | Substrate for biotin protein ligase; links to fatty acid synthesis |
| accC | Biotin carboxylase; catalyzes first step of fatty acid synthesis | Downstream of biotinylation; potential target for metabolic engineering |
| pyc | Pyruvate carboxylase; biotin-dependent enzyme | Requires biotinylation by BirA; involved in gluconeogenesis |
| mccA | Methylcrotonyl-CoA carboxylase; biotin-dependent | Defects cause organic acidemia; model for biotin ligase studies |
| pccB | Propionyl-CoA carboxylase; biotin-dependent | Mutations lead to propionic acidemia; requires BirA-mediated biotinylation |
| hlcs | Holocarboxylase synthetase; human biotin protein ligase | Mutations cause holocarboxylase synthetase deficiency |
| rubisco | Ribulose-1,5-bisphosphate carboxylase/oxygenase; fixes CO2 | Not a ligase but involved in carbon fixation; studied alongside C-C bond-forming enzymes |
| acs | Acetyl-CoA synthase; forms C-C bond in Wood-Ljungdahl pathway | Model for anaerobic carbon fixation; potential for biofuel production |
| pckA | Phosphoenolpyruvate carboxykinase; forms C-C bond in gluconeogenesis | Uses CO2 and GTP/ATP; relevant to metabolic engineering |
| ppc | Phosphoenolpyruvate carboxylase; fixes CO2 to form oxaloacetate | Key enzyme in C4 photosynthesis; target for crop improvement |
| cadA | Lysine decarboxylase; not a ligase but related to C-C bond metabolism | Indirectly linked; used as control in metabolic studies |
| bioB | Biotin synthase; forms C-S bonds in biotin synthesis | Upstream of BirA; part of biotin operon |
| bioF | 8-amino-7-oxononanoate synthase; forms C-C bond in biotin synthesis | Directly forms a C-C bond; potential model for GO:0016885 |
| bioA | Adenosylmethionine-8-amino-7-oxononanoate aminotransferase | Involved in biotin synthesis; not a ligase but related pathway |
| bioD | Dethiobiotin synthetase; ATP-dependent, forms C-N bond | Uses ATP; part of biotin synthesis; contrast to C-C ligases |
| bioH | Pimeloyl-ACP methyl ester carboxylesterase | Biotin synthesis; upstream of C-C bond-forming steps |
How Is ligase activity, forming carbon-carbon bonds Regulated?
The activity of carbon-carbon bond-forming ligases is regulated at multiple levels. In biotin protein ligase, expression of the birA gene is controlled by a biotin-responsive repressor in bacteria, and the enzyme's activity can be modulated by feedback inhibition by biotinyl-5'-AMP. In humans, holocarboxylase synthetase (HLCS) is regulated by biotin availability and may be subject to post-translational modifications. Additionally, the availability of ATP and substrates can influence the rate of catalysis. However, specific regulatory mechanisms for many enzymes in this GO class remain to be fully elucidated.
ligase activity, forming carbon-carbon bonds and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HLCS | Holocarboxylase synthetase deficiency | Knockout human cell lines (e.g., HEK293) and patient-derived fibroblasts |
| PCCB | Propionic acidemia | Point-mutation knock-in mice or patient iPSCs |
| MCCC1 | Methylmalonic acidemia | CRISPR knockout in HepG2 cells |
| PC | Pyruvate carboxylase deficiency | Knock-in of patient mutations in neuroblastoma cells |
| birA (bacterial) | Biotin auxotrophy | Knockout in E. coli for antibiotic target studies |
Holocarboxylase Synthetase Deficiency
Mutations in the human HLCS gene, which encodes a biotin protein ligase, cause holocarboxylase synthetase deficiency, a rare autosomal recessive disorder characterized by impaired biotinylation of carboxylases. This leads to metabolic acidosis, skin rash, and neurological symptoms. The disease highlights the critical role of GO:0016885 in human metabolism.
Propionic Acidemia and Methylmalonic Acidemia
Defects in biotin-dependent carboxylases, such as propionyl-CoA carboxylase and methylcrotonyl-CoA carboxylase, which require biotinylation by holocarboxylase synthetase, result in propionic acidemia and methylmalonic acidemia. These disorders underscore the importance of carbon-carbon bond-forming ligases in maintaining metabolic homeostasis.
Cancer Metabolism
Altered carbon fixation and carboxylation pathways are increasingly recognized in cancer cells, where enzymes like pyruvate carboxylase support anabolic growth. Although direct mutations in GO:0016885 enzymes are not common, their activity can be hijacked to sustain tumor metabolism, making them potential therapeutic targets.
From ligase activity, forming carbon-carbon bonds-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of BirA loss on cell viability? | CRISPR knockout in HeLa or HEK293 cells |
| How does a specific active-site mutation affect catalysis? | Point mutation (e.g., K183A) knock-in in bacterial or human cells |
| Can a disease-associated HLCS mutation be corrected? | Knock-in of wild-type HLCS in patient iPSCs |
| Where is the enzyme localized? | Tagged knock-in (e.g., GFP-HLCS) in mammalian cells |
| Does overexpression alter metabolic flux? | Overexpression of birA or HLCS in E. coli or human cells |
| What genes interact with the ligase? | CRISPR library screening in knockout backgrounds |
How to Study the ligase activity, forming carbon-carbon bonds Process
| Method | What It Measures | Typical Application |
|---|---|---|
| X-ray crystallography | 3D structure of enzyme-substrate complexes | Active-site mapping of biotin protein ligase |
| Isothermal titration calorimetry | Binding affinity of substrates/ATP | Quantifying substrate specificity |
| ATP hydrolysis assay | Rate of ATP consumption | Kinetic characterization of ligases |
| Mass spectrometry | Product formation and intermediate detection | Identifying biotinyl-5'-AMP intermediate |
| CRISPR knockout screening | Gene essentiality and synthetic lethality | Identifying pathways that depend on C-C ligases |
| RNA-seq | Transcriptional changes upon ligase perturbation | Uncovering regulatory networks |
| Proteomics | Protein expression and post-translational modifications | Detecting biotinylation of carboxylases |
Structural Biology
X-ray crystallography and cryo-EM can determine the three-dimensional structures of carbon-carbon bond-forming ligases in complex with substrates and ATP analogues. These methods reveal active-site architecture and conformational changes during catalysis, as demonstrated for biotin protein ligase.
Computational Chemistry
Quantum mechanical calculations, such as atom-condensed Fukui function analysis, can model the electronic properties of substrates and transition states, providing insights into the mechanism of enzymatic CO2 fixation and C-C bond formation.
Enzymatic Assays
In vitro assays using purified enzymes and radiolabeled or fluorescent substrates can measure ligase activity by monitoring ATP hydrolysis or product formation. These assays are essential for kinetic characterization and inhibitor screening.
CRISPR Screening
Genome-wide CRISPR knockout or activation screens can identify genes that modulate sensitivity to ligase inhibitors or that compensate for loss of a specific carbon-carbon bond-forming ligase. Such screens link genotype to phenotype in a high-throughput manner.
How CRISPR Can Be Used to Study GO:0016885 ligase activity, forming carbon-carbon bonds
Knockout
CRISPR knockout of genes encoding carbon-carbon bond-forming ligases, such as birA or HLCS, can reveal their essentiality and downstream metabolic consequences. For example, knocking out HLCS in human cells leads to defective biotinylation of carboxylases, mimicking holocarboxylase synthetase deficiency.
Point Mutation
Introducing specific point mutations (e.g., in the ATP-binding site) via CRISPR base editing or homology-directed repair allows researchers to dissect catalytic residues and separate ligase activity from other functions. Such models are invaluable for understanding disease-associated mutations.
Knock-in
Knock-in of tagged versions (e.g., GFP or FLAG) of ligase genes enables live-cell imaging and proteomic analysis of localization and interaction partners. Knock-in of patient mutations can create isogenic disease models for drug testing.
Overexpression
CRISPR activation (CRISPRa) or cDNA overexpression can increase ligase levels to study gain-of-function effects, such as enhanced carbon fixation or metabolic flux. Overexpression models are useful for biotechnological applications.
How EDITGENE Supports ligase activity, forming carbon-carbon bonds Research
Researchers studying ligase activity, forming carbon-carbon bonds-related genes often need to determine whether a candidate gene is causally involved in a specific metabolic or disease phenotype. EDITGENE provides a comprehensive suite of CRISPR-based services to create precisely engineered cell models, enabling functional validation of genes in the GO:0016885 pathway.
Contact EDITGENE today to design your custom CRISPR model for ligase activity, forming carbon-carbon bonds research.
Frequently Asked Questions About ligase activity, forming carbon-carbon bonds
What is ligase activity, forming carbon-carbon bonds?
It is a molecular function (GO:0016885) that catalyzes the joining of two molecules via a carbon-carbon bond, coupled to ATP hydrolysis.
What genes are involved in ligase activity, forming carbon-carbon bonds?
Key genes include birA (biotin protein ligase), HLCS (holocarboxylase synthetase), and various carboxylases that accept biotin.
What is the role of biotin protein ligase in carbon-carbon bond formation?
Biotin protein ligase activates biotin to biotinyl-5'-AMP, which is then transferred to carboxylases, enabling subsequent carbon-carbon bond formation in fatty acid synthesis.
How is GO:0016885 studied experimentally?
Researchers use X-ray crystallography, enzymatic assays, and CRISPR knockout models to study the structure, kinetics, and cellular roles of these ligases.
What diseases are associated with defects in carbon-carbon bond-forming ligases?
Mutations in HLCS cause holocarboxylase synthetase deficiency, and defects in biotin-dependent carboxylases lead to propionic acidemia and methylmalonic acidemia.
Can CRISPR be used to study ligase activity, forming carbon-carbon bonds?
Yes, CRISPR knockout, point mutation, and knock-in models allow precise dissection of gene function and disease mechanisms.
What is the mechanism of ATP-dependent carbon-carbon bond formation?
ATP is hydrolyzed to activate one substrate, which then attacks another to form a C-C bond, as seen in biotin activation and CO2 fixation.
Which model organisms are used to study GO:0016885?
Bacteria (e.g., E. coli, Pyrococcus horikoshii), yeast, and human cell lines are commonly used.
How does EDITGENE support research on ligase activity, forming carbon-carbon bonds?
EDITGENE provides custom CRISPR cell models, library screening, and bioinformatics services tailored to genes in this pathway.
What are the key structural features of biotin protein ligase?
It has a Rossmann-like fold that binds ATP and biotin, with a flexible loop that closes over the active site during catalysis.
Conclusion
GO:0016885 (ligase activity, forming carbon-carbon bonds) represents a vital enzymatic function that underpins numerous biosynthetic pathways, from biotin activation to carbon fixation. Structural and computational studies have illuminated the catalytic mechanisms, while genetic and disease models highlight its physiological importance. Continued research using CRISPR and other advanced tools will further unravel the roles of these ligases in health and disease, and may lead to novel therapeutic and biotechnological applications.
References
- 1. Oller J et al.. 2020. Atom-Condensed Fukui Function in Condensed Phases and Biological Systems and Its Application to Enzymatic Fixation of Carbon Dioxide.. J Phys Chem A 124(5):849-857 PMID: 31951411
- 2. Bagautdinov B et al.. 2005. Crystal structures of biotin protein ligase from Pyrococcus horikoshii OT3 and its complexes: structural basis of biotin activation.. J Mol Biol 353(2):322-33 PMID: 16169557
