GO:0050152 omega-amidase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0050152 (omega-amidase activity) catalyzes the hydrolysis of monoamides of dicarboxylic acids, converting 2-oxosuccinamate to oxaloacetate and 2-oxoglutaramate to 2-oxoglutarate, releasing ammonium.
• The enzyme is functionally coupled with glutamine transaminases in the glutamine transaminase-omega-amidase pathway, which contributes to glutamine catabolism and alpha-ketoglutarate generation.
• Human omega-amidase is encoded by NIT2, a putative tumor suppressor also known as Nit2, and its catalytic active site has been structurally characterized.
• The pathway senses oxidative stress and regulates glutamine metabolism and alpha-ketoglutarate levels in endothelial cells.
• Species variations in brain omega-amidase activity and effects of portacaval shunting have been documented, suggesting neurological relevance.
• Biocatalytic production of alpha-ketoglutaramate and efficient recombinant expression of human omega-amidase enable biochemical and structural studies.
Description
Omega-amidase activity (GO:0050152) is a molecular function defined as the catalysis of the reaction: a monoamide of a dicarboxylic acid + H2O = a dicarboxylate + NH4+. Substrates include 2-oxosuccinamate and 2-oxoglutaramate, which are converted to oxaloacetate and 2-oxoglutarate, respectively. This activity is essential for the glutamine transaminase-omega-amidase pathway, a route for glutamine catabolism that generates alpha-keto acids and ammonium. The enzyme is widely distributed across species, with variations in brain activity reported. In humans, omega-amidase is encoded by NIT2, a putative tumor suppressor, and its catalytic mechanism has been studied by kinetic assays and molecular dynamics simulations. The pathway has been shown to sense oxidative stress and control glutamine metabolism and alpha-ketoglutarate levels in endothelial cells. Understanding omega-amidase activity is therefore important for researchers studying nitrogen metabolism, redox biology, and cancer.
omega-amidase activity At A Glance
| GO ID | GO:0050152 |
|---|---|
| GO term | omega-amidase activity |
| Ontology | molecular_function |
| Synonym | alpha-keto acid-omega-amidase activity; omega-amidodicarboxylate amidohydrolase activity; w-amidase activity |
| Major function | Catalysis of the hydrolysis of monoamides of dicarboxylic acids to dicarboxylates and ammonium |
| Substrates | 2-oxosuccinamate, 2-oxoglutaramate |
| Products | oxaloacetate, 2-oxoglutarate, ammonium |
| Coupled pathway | Glutamine transaminase-omega-amidase pathway |
| Human gene | NIT2 (Nit2) |
What Is GO:0050152?
Omega-amidase activity (GO:0050152) is the catalytic function of hydrolyzing a monoamide of a dicarboxylic acid to yield a dicarboxylate and ammonium. The enzyme accepts substrates such as 2-oxosuccinamate and 2-oxoglutaramate, producing oxaloacetate and 2-oxoglutarate, respectively. This activity is synonymous with alpha-keto acid-omega-amidase activity, omega-amidodicarboxylate amidohydrolase activity, and w-amidase activity. It is functionally coupled with glutamine transaminases, forming the glutamine transaminase-omega-amidase pathway.
Why Is omega-amidase activity Important in Cell Biology?
Omega-amidase activity is a key step in the glutamine transaminase-omega-amidase pathway, which links glutamine catabolism to the production of alpha-keto acids such as alpha-ketoglutarate, a central metabolite in the TCA cycle and a cofactor for dioxygenases. This pathway is involved in nitrogen disposal and has been implicated in oxidative stress sensing in endothelial cells. The human enzyme, NIT2, is a putative tumor suppressor, and its dysfunction may contribute to cancer. Moreover, the enzyme is conserved from bacteria to humans, and its activity has been detected in brain, where species variations and effects of portacaval shunting suggest neurological roles. Thus, omega-amidase activity is important for understanding metabolic reprogramming, redox homeostasis, and disease mechanisms.
• Provides a route for glutamine catabolism via the glutamine transaminase-omega-amidase pathway.
• Generates alpha-ketoglutarate, a key TCA cycle intermediate and cofactor for many enzymes.
• Senses oxidative stress and regulates glutamine metabolism in endothelial cells.
• Human NIT2 is a putative tumor suppressor, linking omega-amidase activity to cancer.
• Enables detoxification of alpha-keto acid amides such as 2-oxoglutaramate.
• Shows species-specific brain activity and is affected by portacaval shunting, suggesting neurological relevance.
• Is functionally coupled with glutamine transaminases, integrating amino acid and energy metabolism.
• Biocatalytic synthesis of alpha-ketoglutaramate using omega-amidase enables metabolic studies.
• Recombinant production of human omega-amidase facilitates structural and kinetic analyses.
• The enzyme is conserved in fungi such as Neurospora crassa, where it participates in glutamine degradation.
What Happens During omega-amidase activity?
Substrate recognition and binding
In simple terms: The enzyme grabs a specific molecule called a monoamide of a dicarboxylic acid.
Omega-amidase binds substrates such as 2-oxosuccinamate and 2-oxoglutaramate, which are monoamides of dicarboxylic acids. The active site of human Nit2/omega-amidase has been characterized by kinetic assays and molecular dynamics simulations, revealing key residues involved in substrate binding.
Catalytic hydrolysis
In simple terms: Water is used to split the amide bond, releasing ammonium and a dicarboxylate.
The enzyme catalyzes the hydrolysis of the monoamide, converting 2-oxosuccinamate to oxaloacetate and 2-oxoglutaramate to 2-oxoglutarate, with release of ammonium. This reaction is essential for the glutamine transaminase-omega-amidase pathway, which couples transamination of glutamine to alpha-keto acids with subsequent amide hydrolysis.
Coupling with glutamine transaminases
In simple terms: The enzyme works together with another enzyme to break down glutamine.
Omega-amidase is functionally coupled with glutamine transaminases, forming the glutamine transaminase-omega-amidase pathway. In this pathway, glutamine is transaminated to alpha-ketoglutaramate, which is then hydrolyzed by omega-amidase to alpha-ketoglutarate and ammonium.
Role in oxidative stress sensing
In simple terms: The pathway helps cells respond to oxidative stress by adjusting glutamine use.
The transaminase-omega-amidase pathway senses oxidative stress to control glutamine metabolism and alpha-ketoglutarate levels in endothelial cells. This suggests that omega-amidase activity is part of a metabolic sensing mechanism that maintains redox balance.
Species distribution and tissue expression
In simple terms: The enzyme is found in many organisms and tissues, with some differences.
Omega-amidase activity has been detected in various species, with variations in brain activity and effects of portacaval shunting. In Neurospora crassa, the omega-amidase pathway participates in glutamine degradation. Human omega-amidase (Nit2) can be efficiently produced in Escherichia coli for study.
Key Genes Involved in GO:0050152 omega-amidase activity
The following genes and proteins are directly associated with omega-amidase activity (GO:0050152) and its coupled pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| NIT2 (human) | Encodes omega-amidase (Nit2), a putative tumor suppressor | Studied for catalytic mechanism, cancer link, and metabolic regulation |
| GLS (human) | Glutaminase, converts glutamine to glutamate | Upstream of glutamine transaminase-omega-amidase pathway |
| GPT (human) | Glutamine transaminase, produces alpha-ketoglutaramate | Coupled with omega-amidase in the pathway |
| GGT (human) | Gamma-glutamyl transpeptidase, involved in glutathione metabolism | May influence glutamine/glutamate pools linked to omega-amidase |
| GLUD1 (human) | Glutamate dehydrogenase, produces alpha-ketoglutarate | Alternative route to alpha-ketoglutarate, related to omega-amidase pathway |
| NIT2 (mouse) | Ortholog of human NIT2 | Model for knockout and metabolic studies |
| Nit2 (rat) | Ortholog of human NIT2 | Used in brain activity studies |
| nit-2 (Neurospora crassa) | Omega-amidase in filamentous fungus | Model for glutamine degradation |
| NIT2 (E. coli recombinant) | Recombinant human omega-amidase | Biochemical and structural studies |
| GOT1 (human) | Aspartate aminotransferase, links to oxaloacetate | Oxaloacetate is product of omega-amidase on 2-oxosuccinamate |
| GOT2 (human) | Mitochondrial aspartate aminotransferase | May interact with omega-amidase products |
| MDH1 (human) | Malate dehydrogenase, uses oxaloacetate | Downstream of omega-amidase product |
| MDH2 (human) | Mitochondrial malate dehydrogenase | Downstream of omega-amidase product |
| IDH1 (human) | Isocitrate dehydrogenase, uses alpha-ketoglutarate | Downstream of omega-amidase product |
| IDH2 (human) | Mitochondrial isocitrate dehydrogenase | Downstream of omega-amidase product |
| SLC1A5 (human) | Glutamine transporter | Regulates glutamine availability for the pathway |
| SLC7A5 (human) | L-type amino acid transporter | Influences glutamine and essential amino acid uptake |
How Is omega-amidase activity Regulated?
The transaminase-omega-amidase pathway is regulated by oxidative stress, which controls glutamine metabolism and alpha-ketoglutarate levels in endothelial cells. This suggests that omega-amidase activity is not constitutive but responds to redox signals. Additionally, species variations in brain activity and effects of portacaval shunting indicate that enzyme levels or activity can be modulated by physiological or pathological states. However, specific transcriptional or post-translational regulators of NIT2 remain to be fully defined.
omega-amidase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| NIT2 | Cancer (putative tumor suppressor) | NIT2 knockout cancer cell lines; xenograft models |
| NIT2 | Oxidative stress response | Endothelial cells with NIT2 knockdown or overexpression |
| NIT2 | Hepatic encephalopathy | Portacaval shunting animal models; brain tissue analysis |
| NIT2 | Glutamine metabolism disorders | Metabolic flux assays in NIT2-edited cells |
| NIT2 | Neurospora crassa glutamine degradation | Fungal genetics and enzyme assays |
Cancer
Human NIT2, encoding omega-amidase, is a putative tumor suppressor. Loss of NIT2 function may contribute to tumorigenesis by altering glutamine metabolism and alpha-ketoglutarate levels, which are critical for cancer cell proliferation.
Neurological and hepatic disorders
Omega-amidase activity in brain shows species variations and is affected by portacaval shunting, a model of hepatic encephalopathy. This suggests a role in ammonia detoxification and neurological function, although direct disease mechanisms require further study.
Metabolic and oxidative stress disorders
The transaminase-omega-amidase pathway senses oxidative stress and regulates glutamine metabolism in endothelial cells. Dysregulation may contribute to endothelial dysfunction and metabolic disorders associated with oxidative stress.
From omega-amidase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of NIT2 loss on glutamine metabolism? | NIT2 knockout cell lines (e.g., HEK293, HeLa) |
| How does a point mutation in the active site affect catalysis? | Point-mutation knock-in of NIT2 catalytic residues |
| Can tagged NIT2 be used to study localization? | Knock-in of FLAG- or GFP-tagged NIT2 |
| Does NIT2 overexpression alter alpha-ketoglutarate levels? | Overexpression of NIT2 in endothelial cells |
| What is the role of NIT2 in tumor growth? | NIT2 knockout xenograft models |
| How is omega-amidase activity regulated by oxidative stress? | NIT2 reporter or activity assays under oxidative stress |
How to Study the omega-amidase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic activity assay | Hydrolysis of 2-oxoglutaramate to 2-oxoglutarate and ammonium | Kinetic characterization of omega-amidase |
| Molecular dynamics simulation | Active site dynamics and substrate binding | Mechanistic studies of human Nit2 |
| 15N-glutamine tracing | Flux through glutamine transaminase-omega-amidase pathway | Metabolic reprogramming in cells |
| Recombinant protein production | Yield and purity of human omega-amidase | Biochemical and structural studies |
| Biocatalytic synthesis | Production of alpha-ketoglutaramate | Substrate preparation for assays |
| Western blot | Protein expression levels of NIT2 | Knockout/overexpression validation |
| CRISPR knockout screening | Gene essentiality and metabolic dependencies | Cancer cell line panels |
| RNA-seq | Transcriptional changes upon NIT2 perturbation | Pathway analysis |
Enzymatic activity assays
Omega-amidase activity can be measured by monitoring the hydrolysis of 2-oxoglutaramate to 2-oxoglutarate and ammonium, using coupled enzymatic assays or HPLC. Kinetic parameters and substrate specificity are determined with purified enzyme.
Structural and computational studies
The catalytic active site of human Nit2/omega-amidase has been studied by kinetic assays and molecular dynamics simulations, revealing key residues and reaction mechanisms. X-ray crystallography and homology modeling can further elucidate structure-function relationships.
Metabolic flux analysis
Stable isotope tracing with 15N-glutamine can track flux through the glutamine transaminase-omega-amidase pathway, measuring production of 2-oxoglutaramate and alpha-ketoglutarate. This is useful in endothelial cells and cancer models.
Expression and production
Recombinant human omega-amidase can be efficiently produced in Escherichia coli for biochemical studies. Biocatalytic synthesis of alpha-ketoglutaramate using omega-amidase enables substrate generation.
How CRISPR Can Be Used to Study GO:0050152 omega-amidase activity
Knockout
CRISPR knockout of NIT2 can eliminate omega-amidase activity, enabling studies of glutamine metabolism, alpha-ketoglutarate levels, and tumor suppressor function. Knockout cell lines are valuable for metabolic flux analysis and drug sensitivity testing.
Point Mutation
Point mutations in the catalytic residues of NIT2 can be introduced by CRISPR to dissect the enzymatic mechanism and separate catalytic activity from potential non-enzymatic functions. Such models help validate active site residues identified by molecular dynamics.
Knock-in
Knock-in of epitope tags (e.g., FLAG, GFP) into the endogenous NIT2 locus allows for localization and interaction studies under native regulation. Knock-in of disease-associated variants can model their effects on omega-amidase activity.
Overexpression
CRISPR activation or cDNA overexpression of NIT2 can increase omega-amidase activity, allowing gain-of-function studies on glutamine metabolism and oxidative stress response. Overexpression models are useful for testing whether increased enzyme activity protects against metabolic stress.
How EDITGENE Supports omega-amidase activity Research
Researchers studying omega-amidase activity-related genes often need to determine whether a candidate gene is causally involved in metabolic pathways, disease phenotypes, or drug responses. Precise genetic models are essential to link NIT2 and its partners to glutamine metabolism and alpha-ketoglutarate production.
Contact EDITGENE today to design your custom CRISPR model for omega-amidase activity research.
Frequently Asked Questions About omega-amidase activity
What is omega-amidase activity?
Omega-amidase activity (GO:0050152) is the catalysis of the hydrolysis of a monoamide of a dicarboxylic acid to a dicarboxylate and ammonium, using substrates such as 2-oxosuccinamate and 2-oxoglutaramate.
What genes are involved in omega-amidase activity?
The human gene NIT2 encodes omega-amidase (Nit2), a putative tumor suppressor. Other genes in the coupled pathway include glutamine transaminases and glutaminase.
What is the glutamine transaminase-omega-amidase pathway?
It is a metabolic pathway that couples transamination of glutamine to alpha-keto acids with hydrolysis of the resulting alpha-keto acid amides by omega-amidase, producing alpha-ketoglutarate and ammonium.
How is omega-amidase activity measured?
It can be measured by enzymatic assays monitoring the conversion of 2-oxoglutaramate to 2-oxoglutarate and ammonium, often coupled with dehydrogenase reactions.
What diseases are associated with omega-amidase activity?
NIT2 is a putative tumor suppressor, and the pathway is linked to cancer and oxidative stress-related endothelial dysfunction. Brain activity changes after portacaval shunting suggest neurological relevance.
What is the role of NIT2 in cancer?
NIT2 is considered a putative tumor suppressor, and its loss may alter glutamine metabolism and alpha-ketoglutarate levels, supporting cancer cell growth.
Can omega-amidase be produced recombinantly?
Yes, human omega-amidase (Nit2) has been efficiently produced in Escherichia coli for biochemical studies.
What substrates does omega-amidase use?
It uses monoamides of dicarboxylic acids, including 2-oxosuccinamate and 2-oxoglutaramate, converting them to oxaloacetate and 2-oxoglutarate, respectively.
Is omega-amidase conserved across species?
Yes, omega-amidase activity has been detected in bacteria, fungi, and mammals, with species variations in brain activity.
How can CRISPR help study omega-amidase activity?
CRISPR knockout, point mutation, knock-in, and overexpression models allow precise manipulation of NIT2 to study its role in metabolism and disease.
Conclusion
Omega-amidase activity (GO:0050152) is a fundamental enzymatic function that links glutamine catabolism to alpha-ketoglutarate production and ammonium release. Its human representative, NIT2, is a putative tumor suppressor and a key node in oxidative stress sensing and metabolic regulation. Understanding this activity requires integrating structural, kinetic, and metabolic approaches, and CRISPR-based models are powerful tools to dissect its roles in health and disease. Continued research on omega-amidase will likely reveal new therapeutic opportunities in cancer and metabolic disorders.
References
- 1. Cooper AJ et al.. 1977. The glutamine transaminase-omega-amidase pathway.. CRC Crit Rev Biochem 4(3):281-303 PMID: 319948
- 2. Herrle N et al.. 2026. The transaminase-ω-amidase pathway senses oxidative stress to control glutamine metabolism and α-ketoglutarate levels in endothelial cells.. EMBO J 45(3):820-855 PMID: 41408486
- 3. Chien CH et al.. 2012. Structural insights into the catalytic active site and activity of human Nit2/ω-amidase: kinetic assay and molecular dynamics simulation.. J Biol Chem 287(31):25715-26 PMID: 22674578
- 4. Lockwood AH et al.. 1977. Glutamine transaminase and omega-amidase: species variations in brain activity and effect of portacaval shunting.. J Neurochem 28(3):673-5 PMID: 853308
- 5. Nikulin M et al.. 2021. Preparative Biocatalytic Synthesis of α-Ketoglutaramate.. Int J Mol Sci 22(23) PMID: 34884551
- 6. Epova EY et al.. 2021. A novel efficient producer of human ω-amidase (Nit2) in Escherichia coli.. Anal Biochem 632:114332 PMID: 34391728
- 7. Calderón J et al.. 1985. Omega-amidase pathway in the degradation of glutamine in Neurospora crassa.. J Bacteriol 161(2):807-9 PMID: 2857167
- 8. Jaisson S et al.. 2009. Molecular identification of omega-amidase, the enzyme that is functionally coupled with glutamine transaminases, as the putative tumor suppressor Nit2.. Biochimie 91(9):1066-71 PMID: 19596042
