GO:0004069 L-aspartate:2-oxoglutarate transaminase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004069 describes the molecular function of catalyzing the reversible transfer of an amino group from L-aspartate to 2-oxoglutarate, yielding oxaloacetate and L-glutamate.
• This activity is essential for amino acid metabolism, the malate-aspartate shuttle, and the maintenance of cellular redox balance.
• The enzymes responsible, aspartate aminotransferases (AST/GOT), are pyridoxal phosphate-dependent and exist as cytosolic (GOT1) and mitochondrial (GOT2) isoforms.
• Altered aspartate transaminase activity in serum is a long-established biomarker for liver disease, myocardial infarction, and other tissue damage.
• Bacterial aspartate aminotransferases, such as those in Escherichia coli, show magnesium sensitivity, linking enzyme function to metal homeostasis.
• Studying GO:0004069 requires precise enzymatic assays, structural biology, and CRISPR-based models to dissect isoform-specific roles in health and disease.
Description
L-aspartate:2-oxoglutarate transaminase activity (GO:0004069) is a fundamental molecular function that enables the reversible interconversion of the amino acids aspartate and glutamate with the corresponding keto acids oxaloacetate and 2-oxoglutarate. This reaction, catalyzed by aspartate aminotransferase (AST) enzymes, is a cornerstone of nitrogen metabolism and is conserved across all domains of life. The activity is indispensable for the malate-aspartate shuttle, which transfers reducing equivalents from the cytosol into mitochondria, and for the synthesis of key metabolites such as oxaloacetate, a citric acid cycle intermediate. Researchers have long relied on measuring AST activity in serum as a diagnostic marker for tissue damage, particularly in liver and heart disease. Beyond clinical diagnostics, the enzyme's catalytic mechanism, cofactor requirements, and regulatory properties have been subjects of intense biochemical and structural investigation. Understanding GO:0004069 at the molecular level is therefore critical for both basic cell biology and translational medicine.
L-aspartate:2-oxoglutarate transaminase activity At A Glance
| GO ID | GO:0004069 |
|---|---|
| GO term | L-aspartate:2-oxoglutarate transaminase activity |
| Ontology | molecular_function |
| Synonym | Aspartate aminotransferase activity; Glutamate-oxaloacetate transaminase activity; GOT (enzyme); Transaminase A activity |
| Major function | Catalyzes the reversible transfer of an amino group from L-aspartate to 2-oxoglutarate, yielding oxaloacetate and L-glutamate |
| Cofactor | Pyridoxal 5'-phosphate (PLP) |
| Subcellular location | Cytosol and mitochondria (isoform-dependent) |
| Reaction direction | Reversible |
| Pathway context | Amino acid metabolism; malate-aspartate shuttle; citric acid cycle anaplerosis |
What Is GO:0004069?
GO:0004069 is defined as the catalysis of the reaction: L-aspartate + 2-oxoglutarate = oxaloacetate + L-glutamate. In other words, it is the enzyme activity that transfers an amino group from aspartate to 2-oxoglutarate, producing glutamate and oxaloacetate. This activity is synonymous with aspartate aminotransferase (AST), glutamate-oxaloacetate transaminase (GOT), and several other names listed in QuickGO. The reaction is reversible and requires pyridoxal phosphate as a cofactor.
Why Is L-aspartate:2-oxoglutarate transaminase activity Important in Cell Biology?
GO:0004069 is important because it represents a central node in nitrogen and energy metabolism, linking amino acid breakdown and synthesis to the citric acid cycle and cellular redox homeostasis. The activity is essential for the malate-aspartate shuttle, which is the primary mechanism for transferring reducing equivalents from cytosolic NADH into mitochondria for oxidative phosphorylation. Clinically, aspartate aminotransferase activity in serum is a sensitive biomarker for hepatocellular injury, myocardial infarction, and muscle disorders, making it one of the most frequently ordered laboratory tests worldwide. Moreover, the enzyme's catalytic mechanism and structural dynamics have served as a model system for understanding PLP-dependent transamination, protein evolution, and allosteric regulation. In biotechnology, aspartate aminotransferases are used in biosensors and for the production of chiral amino acids.
• Provides a key step in the malate-aspartate shuttle, essential for mitochondrial redox balance.
• Serves as a diagnostic biomarker for liver disease, myocardial infarction, and muscle damage.
• Participates in amino acid metabolism, linking aspartate and glutamate pools to the citric acid cycle.
• Requires pyridoxal phosphate, making it a model for PLP-dependent enzyme mechanisms.
• Exhibits magnesium sensitivity in bacteria, connecting enzyme activity to metal homeostasis.
• Involved in neurotransmitter metabolism, as shown by studies on L-cycloserine effects on brain GABA.
• Cysteine aminotransferase, a related activity, can also act on aspartate, indicating overlapping substrate specificity.
• Target for drug design in diseases where transaminase activity is dysregulated.
• Used in certified reference materials for enzyme activity standardization.
• Facilitates metabolic engineering for production of oxaloacetate-derived compounds.
Molecular Mechanism of L-aspartate:2-oxoglutarate transaminase activity
Substrate Binding and Cofactor Chemistry
In simple terms: The enzyme uses a helper molecule (PLP) to temporarily hold the amino group from aspartate.
The catalytic cycle begins with the binding of L-aspartate and 2-oxoglutarate to the active site of aspartate aminotransferase. The enzyme requires pyridoxal 5'-phosphate (PLP) as a cofactor, which is covalently linked to a lysine residue. The amino group of aspartate is transferred to PLP, forming pyridoxamine phosphate and releasing oxaloacetate. This step is followed by the transfer of the amino group from pyridoxamine phosphate to 2-oxoglutarate, regenerating PLP and producing L-glutamate. The reaction is reversible and proceeds through a ping-pong bi-bi mechanism.
Structural Asymmetry and Subunit Interactions
In simple terms: The enzyme is made of two identical parts that can behave differently, which affects how it works.
Crystalline aspartate aminotransferase exhibits lattice-induced functional asymmetry of its two subunits, meaning that the two active sites can have different catalytic properties. This asymmetry may play a role in regulation and cooperativity. The enzyme is typically a homodimer, with each subunit containing an active site. Structural studies have revealed that the binding of substrates induces conformational changes that close the active site and facilitate catalysis.
Isoforms and Subcellular Localization
In simple terms: There are two main versions of the enzyme, one in the cytosol and one in mitochondria, which work together in metabolic shuttles.
Aspartate aminotransferase exists as two distinct isoforms: a cytosolic form (GOT1) and a mitochondrial form (GOT2). These isoforms are encoded by separate genes and differ in their kinetic properties and regulation. The cytosolic and mitochondrial isoforms cooperate in the malate-aspartate shuttle, which transfers reducing equivalents from cytosolic NADH to the mitochondrial electron transport chain. The subcellular localization of these isoforms is critical for their metabolic roles, and disruption of the shuttle can affect energy metabolism.
Metal Sensitivity and Inhibition
In simple terms: Some versions of the enzyme are affected by magnesium, and certain chemicals can block its activity.
The L-aspartate:2-oxoglutarate aminotransferase from Escherichia coli exhibits magnesium sensitivity, suggesting that metal ions can modulate its activity. In addition, L-cycloserine, an inhibitor of PLP-dependent enzymes, affects brain GABA metabolism by inhibiting transaminases, including aspartate aminotransferase. These findings highlight that the activity can be regulated by small molecules and metal ions, which may have physiological implications.
Related Enzyme Activities and Substrate Specificity
In simple terms: Other enzymes can also use aspartate, showing that this activity is part of a larger family.
Cysteine aminotransferase from rat liver cytosol can also catalyze the transamination of aspartate, indicating overlapping substrate specificity among aminotransferases. This suggests that GO:0004069 may be carried out by multiple enzymes in different tissues, and that the metabolic context determines which enzyme predominates. Such redundancy complicates the interpretation of knockout studies but also provides robustness to metabolic networks.
Key Genes Involved in GO:0004069 L-aspartate:2-oxoglutarate transaminase activity
The following genes encode enzymes that exhibit L-aspartate:2-oxoglutarate transaminase activity or closely related aminotransferase functions.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GOT1 | Cytosolic aspartate aminotransferase; key in malate-aspartate shuttle | Metabolic studies, cancer metabolism, redox balance |
| GOT2 | Mitochondrial aspartate aminotransferase; participates in malate-aspartate shuttle and amino acid metabolism | Mitochondrial function, energy metabolism, neurodegeneration |
| GOT1L1 | Testis-specific aspartate aminotransferase-like protein | Reproductive biology, sperm function |
| GPT | Alanine aminotransferase; related transaminase with overlapping substrate specificity | Liver disease biomarker, metabolic studies |
| PSAT1 | Phosphoserine aminotransferase; uses glutamate as amino donor | Serine biosynthesis, cancer proliferation |
| KYAT1 | Kynurenine aminotransferase I; can transaminate aspartate | Neurodegeneration, tryptophan metabolism |
| KYAT3 | Kynurenine aminotransferase III; broad substrate specificity | Neuroprotection, metabolic regulation |
| AGXT | Alanine-glyoxylate aminotransferase; peroxisomal enzyme | Primary hyperoxaluria, liver metabolism |
| AGXT2 | Alanine-glyoxylate aminotransferase 2; mitochondrial | Metabolic disorders, hypertension |
| BCAT1 | Branched-chain amino acid transaminase 1 | Cancer metabolism, neurological disorders |
| BCAT2 | Branched-chain amino acid transaminase 2 | Maple syrup urine disease, metabolic studies |
| TAT | Tyrosine aminotransferase | Tyrosinemia, liver metabolism |
| HGD | Homogentisate 1,2-dioxygenase; not a transaminase but in tyrosine catabolism | Alkaptonuria, metabolic disease |
| GOT1 (E. coli) | Bacterial aspartate aminotransferase | Microbiology, enzyme evolution |
| AspC | E. coli aspartate aminotransferase | Antibiotic target research, metabolic engineering |
| TyrB | E. coli tyrosine aminotransferase | Amino acid biosynthesis |
| IlvE | Branched-chain amino acid aminotransferase | Biotechnology, amino acid production |
| CysK | Cysteine synthase; can also transaminate | Sulfur metabolism, antibiotic resistance |
How Is L-aspartate:2-oxoglutarate transaminase activity Regulated?
The activity of L-aspartate:2-oxoglutarate transaminase is regulated at multiple levels. Enzyme abundance is controlled by transcriptional and translational mechanisms in response to metabolic demands. For example, pyridoxal phosphate availability directly affects enzyme activity, as the cofactor is essential for catalysis. In liver disease, altered levels of pyridoxal phosphate and transaminases are observed, indicating a link between cofactor status and enzyme function. Additionally, the enzyme can be inhibited by compounds such as L-cycloserine, which modifies the PLP cofactor. Metal ions like magnesium can modulate activity in bacterial systems. Post-translational modifications and subunit asymmetry may also influence catalytic efficiency. Overall, regulation ensures that transamination is matched to cellular needs for amino acid interconversion and redox balance.
L-aspartate:2-oxoglutarate transaminase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GOT1 | Cancer metabolism, redox balance | Knockout in cancer cell lines; metabolic flux analysis |
| GOT2 | Mitochondrial dysfunction, neurodegeneration | Mitochondria-targeted knockout; neuronal cultures |
| GPT | Liver disease biomarker | Liver-specific knockout; serum enzyme assays |
| KYAT1 | Neurodegeneration, kynurenine pathway | Knockout mice; behavioral studies |
| BCAT1 | Cancer, neurological disorders | Conditional knockout; metabolomics |
Liver Disease and Serum Biomarkers
Elevated serum aspartate aminotransferase activity is a classic biomarker for hepatocellular injury, including viral hepatitis, alcoholic liver disease, and drug-induced liver injury. The enzyme is released from damaged hepatocytes, and its activity is measured alongside alanine aminotransferase to assess liver damage. Pyridoxal phosphate deficiency, common in liver disease, can affect the assay and interpretation of results. Standardization of enzyme activity measurements has been addressed through certified reference materials to ensure clinical accuracy.
Cardiovascular and Muscle Disorders
Aspartate aminotransferase is also found in cardiac and skeletal muscle, and its elevation in serum can indicate myocardial infarction or muscle trauma. Historically, AST was one of the first cardiac biomarkers, although it has largely been replaced by more specific markers like troponin. Nevertheless, it remains part of routine panels in many settings.
Neurological and Metabolic Conditions
Aspartate aminotransferase plays a role in neurotransmitter metabolism, particularly in the brain, where it participates in the malate-aspartate shuttle and glutamate homeostasis. Inhibition of transaminases by L-cycloserine affects GABA levels, linking the activity to seizure susceptibility and neurological disorders. Inborn errors of metabolism affecting transaminases can lead to metabolic imbalances, although they are rare.
Cancer Metabolism
Altered aspartate aminotransferase activity has been implicated in cancer metabolism, where cancer cells reprogram amino acid metabolism to support proliferation. The cytosolic isoform GOT1 is important for maintaining redox balance and supporting growth in certain cancers. Targeting transaminases is being explored as a therapeutic strategy in oncology.
From L-aspartate:2-oxoglutarate transaminase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of GOT1 in cancer cell proliferation? | GOT1 knockout in cancer cell lines (e.g., CRISPR-Cas9) |
| How does GOT2 contribute to mitochondrial metabolism? | GOT2 point mutation (e.g., catalytic dead) knock-in in cell lines |
| Does isoform-specific expression rescue metabolic defects? | Knock-in of tagged GOT1 or GOT2 under endogenous promoter |
| Can overexpression of GOT1 alter redox balance? | Overexpression of GOT1 in HEK293 or hepatocytes |
| What is the effect of PLP deficiency on transaminase activity? | Point mutation in PLP-binding lysine of GOT1 |
| How does magnesium affect bacterial aspartate aminotransferase? | Overexpression of E. coli AspC with magnesium supplementation |
How to Study the L-aspartate:2-oxoglutarate transaminase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Colorimetric AST assay | Enzyme activity in serum or lysates | Clinical diagnostics, liver function tests |
| Isotope tracing | Metabolic flux through transamination | Cancer metabolism, cell culture |
| X-ray crystallography | Three-dimensional structure of enzyme | Mechanistic studies, drug design |
| CRISPR knockout screening | Gene essentiality and pathway dependencies | Functional genomics |
| Western blot | Protein expression levels | Isoform-specific expression |
| Immunofluorescence | Subcellular localization | Mitochondrial vs cytosolic distribution |
| Mass spectrometry | Post-translational modifications | Regulatory mechanisms |
Enzymatic Activity Assays
The most direct method to study GO:0004069 is to measure enzyme activity in biological samples. Classical assays couple the production of oxaloacetate to a colorimetric or fluorometric readout, such as diazonium salt coupling. These assays are used clinically to quantify AST levels in serum and can be adapted for high-throughput screening. Certified reference materials are available to standardize activity measurements.
Structural Biology and Biophysics
X-ray crystallography and cryo-electron microscopy can reveal the atomic structure of aspartate aminotransferases, including substrate binding and conformational changes. Studies on crystalline enzyme have demonstrated lattice-induced asymmetry, providing insights into allosteric regulation. Isothermal titration calorimetry and surface plasmon resonance can measure substrate and cofactor binding affinities.
Genomic and Proteomic Approaches
CRISPR-Cas9 knockout screens can identify genes required for transaminase activity or for metabolic pathways that depend on it. Proteomics can quantify enzyme abundance and post-translational modifications. Metabolomics, especially isotope tracing, can track the flux through transamination reactions in cells and tissues.
Imaging and Subcellular Localization
Fluorescent tagging of GOT1 and GOT2 allows visualization of their subcellular localization in live cells. This is particularly useful for studying the malate-aspartate shuttle and mitochondrial dynamics. Immunohistochemistry can detect enzyme expression in tissue sections, aiding in the diagnosis of liver and muscle diseases.
How CRISPR Can Be Used to Study GO:0004069 L-aspartate:2-oxoglutarate transaminase activity
Knockout
CRISPR-Cas9 knockout of GOT1 or GOT2 can reveal their specific roles in cellular metabolism. For example, GOT1 knockout in cancer cells may impair proliferation and redox homeostasis, while GOT2 knockout can disrupt mitochondrial function. These models are valuable for dissecting isoform-specific functions and for identifying compensatory pathways.
Point Mutation
Introducing point mutations in the catalytic lysine or substrate-binding residues of GOT1/GOT2 can abolish enzyme activity without affecting protein stability. Such models help distinguish between catalytic activity and non-enzymatic functions. Point mutations can also mimic disease-associated variants identified in patients.
Knock-in
Knock-in of tagged versions (e.g., FLAG, GFP) of GOT1 or GOT2 at endogenous loci allows for real-time tracking of protein localization and interaction partners. This approach preserves native regulation and can be combined with live-cell imaging to study the malate-aspartate shuttle.
Overexpression
Overexpression of wild-type or mutant GOT1/GOT2 in cell lines can test gain-of-function effects on metabolism, redox balance, and cell growth. Overexpression models are particularly useful for studying the consequences of elevated transaminase activity in cancer and metabolic disorders.
How EDITGENE Supports L-aspartate:2-oxoglutarate transaminase activity Research
Researchers studying L-aspartate:2-oxoglutarate transaminase activity-related genes often need to determine whether a candidate gene is causally involved in a specific metabolic or disease phenotype. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of genes encoding aspartate aminotransferases and related enzymes.
Contact EDITGENE today to design your custom CRISPR model for L-aspartate:2-oxoglutarate transaminase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| GOT2 Knockout HEK293 Cell Line | EDJ-KQ1967 | Human | 2806 | Details Get a Quote |
| GOT1 Knockout HEK293 Cell Line | EDJ-KQ4751 | Human | 2805 | Details Get a Quote |
| GOT1L1 Knockout HEK293 Cell Line | EDJ-KQ9389 | Human | 137362 | Details Get a Quote |
| GOT2 Knockout HCT 116 Cell Line | EDJ-KQ21936 | Human | 2806 | Details Get a Quote |
| GOT2 Knockout HeLa Cell Line | EDJ-KQ21937 | Human | 2806 | Details Get a Quote |
| GOT2 Knockout A-549 Cell Line | EDJ-KQ20640 | Human | 2806 | Details Get a Quote |
| GOT1 Knockout HCT 116 Cell Line | EDJ-KQ26273 | Human | 2805 | Details Get a Quote |
| GOT1 Knockout A-549 Cell Line | EDJ-KQ27508 | Human | 2805 | Details Get a Quote |
| GOT1 Knockout HeLa Cell Line | EDJ-KQ27510 | Human | 2805 | Details Get a Quote |
| GOT1L1 Knockout HeLa Cell Line | EDJ-KQ58372 | Human | 137362 | Details Get a Quote |
| GOT1L1 Knockout A-549 Cell Line | EDJ-KQ66860 | Human | 137362 | Details Get a Quote |
| GOT1L1 Knockout HCT 116 Cell Line | EDJ-KQ75263 | Human | 137362 | Details Get a Quote |
Displaying Records 1 To 12 Of 12 Records
Frequently Asked Questions About L-aspartate:2-oxoglutarate transaminase activity
What is L-aspartate:2-oxoglutarate transaminase activity?
It is the enzyme activity that catalyzes the reversible transfer of an amino group from L-aspartate to 2-oxoglutarate, producing oxaloacetate and L-glutamate, as defined by GO:0004069.
What genes are involved in L-aspartate:2-oxoglutarate transaminase activity?
The main genes are GOT1 (cytosolic) and GOT2 (mitochondrial), which encode aspartate aminotransferases. Other related genes include GPT, PSAT1, and KYAT1.
What is the role of aspartate aminotransferase in the liver?
Aspartate aminotransferase is highly expressed in the liver, and its activity in serum is a biomarker for liver damage. Elevated levels indicate hepatocellular injury.
How is aspartate aminotransferase activity measured?
It is commonly measured using colorimetric assays that couple oxaloacetate production to a dye, or by enzymatic rate assays in clinical laboratories.
What diseases are associated with aspartate aminotransferase?
Elevated AST is associated with liver disease, myocardial infarction, muscle disorders, and certain cancers. Genetic variants can also affect enzyme activity.
What is the difference between GOT1 and GOT2?
GOT1 is the cytosolic isoform, while GOT2 is mitochondrial. They participate in the malate-aspartate shuttle and have distinct metabolic roles.
What cofactor does aspartate aminotransferase require?
It requires pyridoxal 5'-phosphate (PLP) as a cofactor for catalysis.
Can aspartate aminotransferase activity be inhibited?
Yes, compounds like L-cycloserine inhibit PLP-dependent enzymes, including aspartate aminotransferase, affecting neurotransmitter metabolism.
Is aspartate aminotransferase activity affected by magnesium?
In Escherichia coli, the enzyme shows magnesium sensitivity, suggesting metal ions can modulate activity.
How can CRISPR be used to study L-aspartate:2-oxoglutarate transaminase activity?
CRISPR can generate knockout, point mutation, knock-in, and overexpression models of GOT1, GOT2, and related genes to dissect their functions in metabolism and disease.
Conclusion
L-aspartate:2-oxoglutarate transaminase activity (GO:0004069) is a central molecular function in amino acid metabolism and redox biology, with broad implications for human health and disease. The enzymes catalyzing this reaction, particularly GOT1 and GOT2, are essential for the malate-aspartate shuttle, nitrogen balance, and metabolic reprogramming in cancer. Clinically, aspartate aminotransferase remains a cornerstone biomarker for liver and muscle damage. Advances in CRISPR-based models and high-throughput screening are enabling precise dissection of isoform-specific roles and regulatory mechanisms. EDITGENE provides the tools and expertise to accelerate this research, from custom knockout and knock-in cell lines to genome-wide screens and bioinformatics analysis.
References
- 1. Toussaint B et al.. 2010. Traceability of values for catalytic activity concentration of enzymes: a Certified Reference Material for aspartate transaminase.. Clin Chem Lab Med 48(6):795-803 PMID: 20441466
- 2. Morin LG et al.. 1973. Technical improvements in measurement of L -aspartate:2-oxoglutarate aminotransferase activity in serum by diazonium salt coupling.. Clin Chem 19(7):776-8 PMID: 4712526
- 3. Vanderlinde RE. 1986. Review of pyridoxal phosphate and the transaminases in liver disease.. Ann Clin Lab Sci 16(2):79-93 PMID: 3008634
- 4. Wood JD et al.. 1978. Effect of L-cycloserine on brain GABA metabolism.. Can J Physiol Pharmacol 56(1):62-8 PMID: 638858
- 5. Urm E et al.. 1973. Magnesium sensitivity of L-aspartate: 2-oxoglutarate aminotransferase in Escherichia coli.. Biochim Biophys Acta 302(2):249-60 PMID: 4572996
- 6. Masola B et al.. 1985. Transamination pathways influencing L-glutamine and L-glutamate oxidation by rat enterocyte mitochondria and the subcellular localization of L-alanine aminotransferase and L-aspartate aminotransferase.. Biochim Biophys Acta 843(1-2):137-43 PMID: 2865979
- 7. Kirsten H et al.. 1983. Crystalline aspartate aminotransferase: lattice-induced functional asymmetry of the two subunits.. Proc Natl Acad Sci U S A 80(7):1807-10 PMID: 6572940
- 8. Akagi R. 1982. Purification and characterization of cysteine aminotransferase from rat liver cytosol.. Acta Med Okayama 36(3):187-97 PMID: 7113743
