GO:0004075 biotin carboxylase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004075 biotin carboxylase activity is a molecular_function defined as the ATP-dependent carboxylation of a biotin-carboxyl-carrier protein using bicarbonate as the carbon source.
• The reaction proceeds through initial activation of bicarbonate by ATP, forming a carboxyphosphate intermediate, followed by transfer of the carboxyl group to biotin.
• Biotin carboxylase is a component of biotin-dependent carboxylases such as acetyl-CoA carboxylase and pyruvate carboxylase, and in some bacteria it is fused with the biotin carboxyl carrier protein.
• The enzyme belongs to the ATP-grasp superfamily, a large group of enzymes that catalyze ATP-dependent ligation of carboxylate groups.
• Both subunits of the homodimeric Escherichia coli biotin carboxylase must be catalytically active for function, demonstrating half-site reactivity is not sufficient.
• Biotin carboxylase activity is a validated target for chemical inhibition, with small-molecule inhibitors showing potential for antibacterial and metabolic applications.
Description
Biotin carboxylase activity (GO:0004075) is a molecular function that catalyzes the ATP-dependent carboxylation of a biotin-carboxyl-carrier protein, producing carboxybiotin-carboxyl-carrier protein, ADP, and phosphate. This reaction is the first committed step in the biosynthesis of fatty acids and in anaplerotic pathways that replenish tricarboxylic acid cycle intermediates. The enzyme is widely conserved across bacteria, plants, and animals, where it functions as a subunit of multi-domain biotin-dependent carboxylases such as acetyl-CoA carboxylase and pyruvate carboxylase. Researchers study biotin carboxylase activity to understand fundamental carbon fixation mechanisms, to develop antibiotics targeting bacterial fatty acid synthesis, and to modulate metabolic flux in cancer and metabolic disorders. The catalytic mechanism involves activation of bicarbonate by ATP to form a carboxyphosphate intermediate, which then carboxylates the biotin cofactor covalently attached to the biotin carboxyl carrier protein. Structural and biochemical studies have placed biotin carboxylase within the ATP-grasp enzyme superfamily, a diverse group of enzymes that share a common ATP-binding fold. In Escherichia coli, biotin carboxylase functions as a homodimer, and catalytic activity of both subunits is required for overall carboxylation, indicating a half-of-the-sites mechanism is not operative. In some organisms, such as Chloroflexus aurantiacus, biotin carboxylase and biotin carboxyl carrier protein are fused into a single polypeptide, which simplifies the carboxylation reaction and provides insights into enzyme evolution. The activity is also subject to allosteric regulation in certain contexts, as seen in pyruvate carboxylase where acetyl-CoA modulates catalysis. Given its central role in metabolism, biotin carboxylase activity is a focus for both basic enzymology and translational research, including the development of inhibitors and the engineering of microbial production strains.
biotin carboxylase activity At A Glance
| GO ID | GO:0004075 |
|---|---|
| GO term | biotin carboxylase activity |
| Ontology | molecular_function |
| Synonym | biotin carboxylase (component of acetyl CoA carboxylase) activity; biotin-carboxyl-carrier-protein:carbon-dioxide ligase (ADP-forming) activity |
| Major function | ATP-dependent carboxylation of biotin-carboxyl-carrier protein, the first step in biotin-dependent carboxylation reactions |
| Reaction | ATP + biotin-carboxyl-carrier protein + CO2 = ADP + phosphate + carboxybiotin-carboxyl-carrier protein |
| Enzyme class | Ligase (forming carbon-carbon bonds); ATP-grasp superfamily |
| Cofactor | Biotin (covalently attached to the biotin carboxyl carrier protein) |
| Subcellular location | Cytosol (in eukaryotes); cytoplasm (in bacteria); also mitochondrial in some organisms |
What Is GO:0004075?
Biotin carboxylase activity (GO:0004075) is defined by the Gene Ontology as the catalysis of the reaction: ATP + biotin-carboxyl-carrier protein + CO2 = ADP + phosphate + carboxybiotin-carboxyl-carrier protein. In this reaction, the enzyme uses the energy of ATP hydrolysis to activate bicarbonate (CO2) and covalently attach a carboxyl group to the biotin prosthetic group of the biotin-carboxyl-carrier protein. This is the first step in a two-step carboxylation process carried out by biotin-dependent enzymes, and it is essential for the subsequent transfer of the carboxyl group to an acceptor substrate such as acetyl-CoA or pyruvate.
Why Is biotin carboxylase activity Important in Cell Biology?
Biotin carboxylase activity is a critical enzymatic function at the intersection of fatty acid biosynthesis and central carbon metabolism. It catalyzes the first committed step in the production of malonyl-CoA, the building block for fatty acid synthesis, and also participates in anaplerotic reactions that maintain TCA cycle flux. Because of its essential role in bacterial fatty acid synthesis, biotin carboxylase is a promising target for antibiotic development, and small-molecule inhibitors have been characterized. In human health, dysregulation of biotin-dependent carboxylases is linked to metabolic disorders and cancer, where altered lipogenesis supports tumor growth. Understanding the catalytic mechanism and regulation of biotin carboxylase activity is therefore fundamental for both basic biology and therapeutic development.
• Biotin carboxylase activity is the first step in fatty acid biosynthesis, providing malonyl-CoA for lipogenesis.
• It is essential for anaplerotic reactions that replenish TCA cycle intermediates, such as the pyruvate carboxylase reaction.
• The enzyme is a validated target for antibacterial drug discovery due to its essential role in bacterial fatty acid synthesis.
• In cancer, increased lipogenesis often relies on biotin-dependent carboxylases, making this activity relevant to tumor metabolism.
• Biotin carboxylase belongs to the ATP-grasp superfamily, serving as a model for understanding ATP-dependent carboxylation mechanisms.
• The enzyme's requirement for both subunits of the homodimer to be active highlights complex allosteric regulation.
• Fused biotin carboxylase and biotin carboxyl carrier protein domains in some bacteria offer simplified models for studying the reaction.
• Engineering biotin carboxylase activity can enhance production of valuable metabolites like surfactin in Bacillus subtilis.
• Allosteric regulation by acetyl-CoA modulates pyruvate carboxylase, linking biotin carboxylase activity to metabolic signaling.
• Inhibitors of biotin carboxylase provide chemical tools to probe metabolic pathways and may lead to new therapeutics.
Molecular Mechanism of biotin carboxylase activity
Bicarbonate Activation by ATP
In simple terms: The enzyme uses ATP to activate bicarbonate, making it reactive so it can be attached to biotin.
The first step in the reaction catalyzed by biotin carboxylase is the ATP-dependent activation of bicarbonate. The enzyme binds ATP and bicarbonate, and through a mechanism involving the formation of a carboxyphosphate intermediate, the bicarbonate is activated for transfer to biotin. This step is supported by the observation that biotin carboxylase exhibits an intrinsic ATPase activity that is dependent on bicarbonate, providing evidence for the initial activation of HCO3- by ATP. The reaction requires a divalent metal ion, typically Mg2+, which coordinates the phosphate groups of ATP and stabilizes the transition state.
Carboxyl Transfer to Biotin
In simple terms: The activated carbon dioxide is then attached to a biotin molecule that is held by a carrier protein.
Following activation, the carboxyl group is transferred from the carboxyphosphate intermediate to the biotin prosthetic group, which is covalently attached to the biotin-carboxyl-carrier protein (BCCP). This results in the formation of carboxybiotin-carboxyl-carrier protein, the product of the reaction. The biotin moiety is tethered to BCCP via a flexible linker, allowing it to swing between the biotin carboxylase active site and the carboxyltransferase active site in multi-domain carboxylases. In some organisms, such as Chloroflexus aurantiacus, biotin carboxylase and BCCP are fused into a single polypeptide, which may facilitate efficient substrate channeling.
Dimeric Structure and Half-Site Reactivity
In simple terms: The enzyme works as a pair of identical subunits, and both must be active for the reaction to proceed efficiently.
Biotin carboxylase typically functions as a homodimer. In Escherichia coli, it has been shown that catalytic activity of both subunits of the homodimer is required for function, indicating that the enzyme does not exhibit half-of-the-sites reactivity. This suggests that the two active sites cooperate or that both must be competent for catalysis. Structural studies of ATP-grasp enzymes, including biotin carboxylase, have revealed that the active site is formed at the interface of the two subunits, and conformational changes upon ATP binding are important for catalysis.
Allosteric Regulation
In simple terms: The enzyme's activity can be turned up or down by other molecules that bind to a different site.
Biotin carboxylase activity can be subject to allosteric regulation. For example, in the biotin-dependent enzyme pyruvate carboxylase, acetyl-CoA acts as an allosteric activator, stimulating the overall carboxylation reaction. This regulation ensures that the enzyme's activity is coordinated with the metabolic state of the cell. In acetyl-CoA carboxylase, citrate acts as an allosteric activator in eukaryotes, while palmitoyl-CoA inhibits the enzyme, though these effects may primarily target other domains. The allosteric regulation of biotin carboxylase itself is less well understood, but studies on pyruvate carboxylase provide a paradigm for how biotin-dependent enzymes are controlled.
Inhibition by Small Molecules
In simple terms: Certain chemicals can block the enzyme, which is useful for developing antibiotics.
Biotin carboxylase is a target for inhibition by small molecules. For instance, ethyl 4-[[2-chloro-5-(phenylcarbamoyl)phenyl]sulphonylamino]benzoate has been shown to inhibit biotin carboxylase, and its mechanism of inhibition has been characterized. Such inhibitors are of interest for antibacterial development because biotin carboxylase is essential in bacteria. The study of these inhibitors also provides insights into the enzyme's catalytic mechanism and structural flexibility.
Key Genes Involved in GO:0004075 biotin carboxylase activity
The following genes encode proteins that possess biotin carboxylase activity or are directly involved in its function across different organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| accC (E. coli) | Biotin carboxylase subunit of acetyl-CoA carboxylase | Model for studying homodimer cooperativity and catalytic mechanism |
| accB (E. coli) | Biotin carboxyl carrier protein | Provides the biotin attachment site for carboxylation |
| accA (E. coli) | Carboxyltransferase subunit | Completes fatty acid synthesis by transferring carboxyl to acetyl-CoA |
| accD (E. coli) | Carboxyltransferase subunit | Essential for membrane lipid synthesis |
| pyc (human) | Pyruvate carboxylase, contains biotin carboxylase domain | Anaplerosis and gluconeogenesis; allosteric regulation by acetyl-CoA |
| PC (human) | Pyruvate carboxylase | Target for cancer metabolism; activator ganoderic acid T |
| ACACA (human) | Acetyl-CoA carboxylase alpha | Cytosolic lipogenesis; cancer and metabolic disease |
| ACACB (human) | Acetyl-CoA carboxylase beta | Mitochondrial fatty acid oxidation regulation |
| C. aurantiacus accC | Fused biotin carboxylase and BCCP | Simplified model for carboxylation and evolution |
| B. subtilis accC | Biotin carboxylase II | Enhances surfactin production via antisense RNA |
| ATP-grasp enzymes | Superfamily including biotin carboxylase | Structural and mechanistic studies of ATP-dependent ligases |
| Biotin carboxylase (various) | Catalytic component of biotin-dependent enzymes | Target for inhibitor design |
| BCCP (various) | Biotin carrier protein | Substrate for biotin carboxylase; flexible linker |
| Carbamoyl phosphate synthetase | ATP-grasp enzyme | Related mechanism of bicarbonate activation |
| D-alanine--D-alanine ligase | ATP-grasp enzyme | Model for ATP-grasp fold |
| Glutathione synthetase | ATP-grasp enzyme | Related ATP-dependent ligation |
| Pyruvate carboxylase (fungal) | Biotin-dependent enzyme | Allosteric regulation studies |
| Acetyl-CoA carboxylase (plant) | Biotin carboxylase domain | Herbicide target |
How Is biotin carboxylase activity Regulated?
Biotin carboxylase activity is regulated at multiple levels. In pyruvate carboxylase, allosteric activation by acetyl-CoA is well documented, where acetyl-CoA binds to a regulatory domain and stimulates catalysis. This ensures that pyruvate carboxylase activity is high when acetyl-CoA levels are elevated, supporting anaplerosis. In acetyl-CoA carboxylase, citrate activates the enzyme in eukaryotes, promoting fatty acid synthesis when energy and carbon are abundant. Additionally, biotin carboxylase activity can be regulated by post-translational modifications, though specific phosphorylation sites are not well characterized. In bacteria, the expression of biotin carboxylase genes is controlled by global regulators of fatty acid metabolism. The enzyme's activity may also be influenced by the availability of biotin and the biotinylation status of the biotin carboxyl carrier protein. Overall, regulation ensures that biotin carboxylase activity is matched to cellular demands for fatty acids and TCA cycle intermediates.
biotin carboxylase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PC | Pyruvate carboxylase deficiency; lactic acidosis | Knockout or point mutation in human cell lines |
| ACACA | Cancer; lipogenesis | Overexpression or knockout in cancer cell lines |
| ACACB | Metabolic syndrome; fatty acid oxidation | Knockout mouse models |
| accC (bacterial) | Bacterial infection; fatty acid synthesis | Bacterial knockout and inhibitor testing |
| Biotin carboxylase domain | Inhibitor development for antibiotics | Enzyme assays with recombinant protein |
Cancer Metabolism
Altered biotin-dependent carboxylase activity is implicated in cancer. Pyruvate carboxylase, which contains a biotin carboxylase domain, supports anaplerosis in cancer cells, and its activation by ganoderic acid T has been shown to exhibit anti-liver cancer activity. This suggests that modulating biotin carboxylase activity could be a therapeutic strategy in cancers that rely on increased lipogenesis or anaplerosis. Acetyl-CoA carboxylase, which also contains biotin carboxylase activity, is often overexpressed in cancers and is a target for inhibitors.
Metabolic Disorders
Deficiencies in biotin-dependent enzymes, such as pyruvate carboxylase, lead to metabolic disorders including lactic acidosis and neurological symptoms. Although direct mutations in the biotin carboxylase domain are rare, impaired biotin metabolism can affect the activity of multiple carboxylases. Understanding the catalytic mechanism of biotin carboxylase activity is therefore relevant for diagnosing and treating these disorders.
Bacterial Infections
Biotin carboxylase is essential for bacterial fatty acid synthesis, making it a target for antibiotics. Inhibitors of biotin carboxylase, such as the sulfonamide derivative characterized by Craft et al., have shown potential for antibacterial development. The enzyme's conservation across pathogenic bacteria and its distinct active site compared to human enzymes make it an attractive target.
From biotin carboxylase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of loss of biotin carboxylase activity on cell viability? | CRISPR knockout of accC or PC in cell lines |
| How does a specific point mutation affect catalysis? | Point mutation knock-in of catalytic residues |
| Can a tagged version of the enzyme be used for localization studies? | Knock-in of GFP or FLAG tag at endogenous locus |
| Does overexpression of biotin carboxylase enhance metabolic flux? | Overexpression of accC or PC in bacterial or mammalian cells |
| What is the role of allosteric regulation in vivo? | Knock-in of mutations in allosteric sites |
| Can biotin carboxylase inhibitors be tested in a cellular context? | CRISPR knockout of target to confirm specificity |
How to Study the biotin carboxylase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Coupled ATPase assay | ATP hydrolysis coupled to carboxylation | Kinetic characterization and inhibitor screening |
| Radioactive bicarbonate fixation | Incorporation of 14C-bicarbonate into biotin | Enzyme activity assays |
| X-ray crystallography | Three-dimensional structure | Active site and mechanism studies |
| CRISPR knockout | Loss of gene function | Essentiality and metabolic studies |
| Antisense RNA | Downregulation of gene expression | Metabolic engineering |
| Isotope tracing | Metabolic flux | Cancer metabolism and anaplerosis |
| Enzyme inhibition assays | IC50 and mechanism of inhibition | Drug discovery |
| Allosteric regulation assays | Effect of effectors on activity | Studying acetyl-CoA activation |
Enzymatic Assays
Biotin carboxylase activity is typically measured using coupled enzyme assays that monitor the formation of ADP or the incorporation of radiolabeled bicarbonate into biotin. The ATPase activity of biotin carboxylase can be measured in the presence of bicarbonate to provide evidence for activation. These assays are used to determine kinetic parameters and to screen for inhibitors.
Structural Biology
X-ray crystallography and cryo-electron microscopy have been used to determine the structures of biotin carboxylase and related ATP-grasp enzymes, revealing the ATP-binding fold and the active site architecture. Structural studies of the fused biotin carboxylase-BCCP from Chloroflexus aurantiacus have provided insights into substrate channeling.
Genetic Knockout and Knockdown
CRISPR-Cas9 knockout of genes encoding biotin carboxylase or its carrier protein can be used to study the essentiality of the activity in various organisms. For example, knockout of accC in E. coli results in fatty acid auxotrophy. Antisense RNA strategies have been used to downregulate biotin carboxylase II in Bacillus subtilis to enhance surfactin production.
Metabolic Flux Analysis
Isotope tracing with 13C-labeled substrates can be used to measure flux through biotin-dependent carboxylases, providing insights into the role of biotin carboxylase activity in central metabolism. This approach has been used to study anaplerosis in cancer cells.
How CRISPR Can Be Used to Study GO:0004075 biotin carboxylase activity
Knockout
CRISPR knockout of genes encoding biotin carboxylase (e.g., accC) or its associated proteins can be used to determine the essentiality of the activity in various cell types. In bacteria, knockout of accC leads to fatty acid auxotrophy, demonstrating its essential role. In mammalian cells, knockout of pyruvate carboxylase (PC) affects anaplerosis and gluconeogenesis.
Point Mutation
Point mutations can be introduced into the catalytic residues of biotin carboxylase to study the mechanism. For example, mutation of the ATP-binding lysine or the bicarbonate-binding residues can abolish activity. Such mutations can be used to confirm the role of specific amino acids in catalysis.
Knock-in
Knock-in of tagged versions of biotin carboxylase (e.g., GFP or FLAG) allows for localization and interaction studies. Knock-in of disease-associated mutations can model metabolic disorders. Additionally, knock-in of the fused biotin carboxylase-BCCP from Chloroflexus aurantiacus into other organisms can be used to study substrate channeling.
Overexpression
Overexpression of biotin carboxylase or its activator can enhance metabolic flux. For example, overexpression of the unconventional biotin carboxylase II in Bacillus subtilis enhanced ACCase activity and surfactin production. Overexpression in mammalian cells can be used to study the effects of increased lipogenesis.
How EDITGENE Supports biotin carboxylase activity Research
Researchers studying biotin carboxylase activity-related genes often need to determine whether a candidate gene is causally involved in a specific metabolic or disease phenotype. This requires precise genetic manipulation, such as knockout, point mutation, knock-in, or overexpression, followed by functional assays. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such studies with high efficiency and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for biotin carboxylase activity research.
Frequently Asked Questions About biotin carboxylase activity
What is biotin carboxylase activity?
Biotin carboxylase activity (GO:0004075) is the ATP-dependent carboxylation of a biotin-carboxyl-carrier protein, producing carboxybiotin-carboxyl-carrier protein, ADP, and phosphate. It is the first step in biotin-dependent carboxylation reactions.
What genes are involved in biotin carboxylase activity?
Genes encoding biotin carboxylase include accC in bacteria, and the biotin carboxylase domains of PC, ACACA, and ACACB in humans. The biotin carboxyl carrier protein is encoded by accB in bacteria.
What is the reaction catalyzed by biotin carboxylase?
The reaction is: ATP + biotin-carboxyl-carrier protein + CO2 = ADP + phosphate + carboxybiotin-carboxyl-carrier protein.
How is biotin carboxylase activity regulated?
It can be allosterically regulated, for example by acetyl-CoA in pyruvate carboxylase, and by citrate in acetyl-CoA carboxylase.
Why is biotin carboxylase a drug target?
Biotin carboxylase is essential for bacterial fatty acid synthesis, making it a target for antibiotics. Inhibitors have been developed and characterized.
What diseases are associated with biotin carboxylase dysfunction?
Deficiencies in biotin-dependent enzymes like pyruvate carboxylase cause metabolic disorders. Altered activity is also linked to cancer metabolism.
What methods are used to study biotin carboxylase activity?
Common methods include enzymatic ATPase assays, radioactive bicarbonate fixation, X-ray crystallography, and CRISPR knockout models.
Can CRISPR be used to study biotin carboxylase?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to study the function of biotin carboxylase genes.
What is the ATP-grasp superfamily?
The ATP-grasp superfamily is a large group of enzymes that share a common ATP-binding fold, including biotin carboxylase, and catalyze ATP-dependent ligation reactions.
How does biotin carboxylase differ from other carboxylases?
Biotin carboxylase is the component that carboxylates biotin, while other domains like carboxyltransferase transfer the carboxyl group to the final acceptor. In some bacteria, biotin carboxylase and biotin carboxyl carrier protein are fused.
Conclusion
Biotin carboxylase activity (GO:0004075) is a fundamental enzymatic function that drives essential metabolic pathways, including fatty acid synthesis and anaplerosis. Its mechanism involves ATP-dependent activation of bicarbonate and carboxyl transfer to biotin, and it is tightly regulated and targeted by inhibitors. Understanding this activity has broad implications for antibacterial drug discovery, cancer metabolism, and metabolic engineering. Researchers can leverage CRISPR-based models to dissect the roles of specific genes and mutations in biotin carboxylase function, accelerating both basic and translational studies.
References
- 1. Lei B et al.. 2025. Ganoderic acid T, a novel activator of pyruvate carboxylase, exhibits potent anti-liver cancer activity.. Metabolism 170:156321 PMID: 40480453
- 2. Shen J et al.. 2024. Chloroflexus aurantiacus acetyl-CoA carboxylase evolves fused biotin carboxylase and biotin carboxyl carrier protein to complete carboxylation activity.. mBio 15(5):e0341423 PMID: 38572988
- 3. Janiyani K et al.. 2001. Function of Escherichia coli biotin carboxylase requires catalytic activity of both subunits of the homodimer.. J Biol Chem 276(32):29864-70 PMID: 11390406
- 4. Fawaz MV et al.. 2011. The ATP-grasp enzymes.. Bioorg Chem 39(5-6):185-91 PMID: 21920581
- 5. Wang M et al.. 2019. Antisense RNA-Based Strategy for Enhancing Surfactin Production in Bacillus subtilis TS1726 via Overexpression of the Unconventional Biotin Carboxylase II To Enhance ACCase Activity.. ACS Synth Biol 8(2):251-256 PMID: 30702274
- 6. Climent I et al.. 1986. ATPase activity of biotin carboxylase provides evidence for initial activation of HCO3- by ATP in the carboxylation of biotin.. Arch Biochem Biophys 251(2):465-70 PMID: 2948446
- 7. Craft MK et al.. 2022. Mechanism of biotin carboxylase inhibition by ethyl 4-[[2-chloro-5-(phenylcarbamoyl)phenyl]sulphonylamino]benzoate.. J Enzyme Inhib Med Chem 37(1):100-108 PMID: 34894987
- 8. Adina-Zada A et al.. 2012. Allosteric regulation of the biotin-dependent enzyme pyruvate carboxylase by acetyl-CoA.. Biochem Soc Trans 40(3):567-72 PMID: 22616868
