GO:0004514 nicotinate-nucleotide diphosphorylase (carboxylating) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004514 describes the molecular function of nicotinate-nucleotide diphosphorylase (carboxylating) activity, also known as QAPRTase or quinolinic acid phosphoribosyltransferase, which catalyzes the reversible conversion of nicotinate D-ribonucleotide, CO2, and diphosphate to quinolinate and 5-phospho-alpha-D-ribose 1-diphosphate.
• This enzyme is a key node in the de novo NAD+ biosynthesis pathway from tryptophan, and its activity directly influences cellular NAD+ levels and downstream NAD+-dependent processes.
• QPRT, the gene encoding this activity, is expressed in a tissue-specific manner, with high levels in kidney, liver, and brain, and its expression is regulated by transcription factors such as HNF4α.
• Dysregulation of this activity has been implicated in aging, inflammation, acute kidney injury, and neurodegenerative conditions, making it a potential therapeutic target.
• Studying GO:0004514 requires a combination of enzymatic assays, metabolic flux analysis, and CRISPR-based genetic models to dissect its role in health and disease.
• EDITGENE provides comprehensive CRISPR services, including knockout, point mutation, knock-in, overexpression, and library screening, to support functional studies of QPRT and related NAD+ pathway genes.
Description
Nicotinate-nucleotide diphosphorylase (carboxylating) activity, encoded by the QPRT gene in humans, is a molecular function that sits at the crossroads of tryptophan catabolism and NAD+ biosynthesis. This enzyme, often referred to as QAPRTase or quinolinic acid phosphoribosyltransferase, catalyzes the reversible decarboxylation and phosphoribosyl transfer that converts nicotinate D-ribonucleotide to quinolinate, a precursor for de novo NAD+ synthesis. The reaction is essential for maintaining cellular NAD+ pools, which are critical for energy metabolism, DNA repair, and signaling. Researchers study GO:0004514 because it represents a key regulatory point in the de novo NAD+ pathway, and its activity can influence a wide range of physiological and pathological processes, from immune function to kidney resilience. The enzyme is also notable for its tissue-specific expression and its sensitivity to cellular stress, which can impair NAD+ biosynthesis in conditions such as acute kidney injury. Understanding the molecular details of this activity is therefore important for developing interventions that modulate NAD+ metabolism. This article provides a comprehensive overview of GO:0004514, covering its definition, biological significance, key genes, regulatory mechanisms, disease associations, and the experimental methods used to study it. By integrating authoritative QuickGO data with verified PubMed literature, we aim to support researchers in designing robust experiments and interpreting their results in the context of NAD+ biology.
nicotinate-nucleotide diphosphorylase (carboxylating) activity At A Glance
| GO ID | GO:0004514 |
|---|---|
| GO term | nicotinate-nucleotide diphosphorylase (carboxylating) activity |
| Ontology | molecular_function |
| Synonym | QAPRTase activity; quinolinic acid phosphoribosyltransferase activity; nicotinate-nucleotide pyrophosphorylase (carboxylating) activity |
| Major function | Catalyzes the reversible conversion of nicotinate D-ribonucleotide, CO2, and diphosphate to quinolinate and 5-phospho-alpha-D-ribose 1-diphosphate, a key step in de novo NAD+ biosynthesis |
| Reaction direction | Reversible; can operate in both directions depending on substrate availability |
| Cofactors | No known cofactors required for catalysis; the reaction involves decarboxylation and phosphoribosyl transfer |
| Subcellular location | Cytosol; the enzyme is part of the cytosolic NAD+ biosynthetic machinery |
| Tissue distribution | High expression in kidney, liver, and brain; lower in other tissues |
What Is GO:0004514?
GO:0004514 is defined as the catalysis of the reaction: CO2 + diphosphate + nicotinate D-ribonucleotide = 5-phospho-alpha-D-ribose 1-diphosphate + 2 H+ + quinolinate. In simpler terms, this activity removes a carboxyl group from nicotinate D-ribonucleotide and transfers a phosphoribosyl group to quinolinate, a step in the de novo synthesis of NAD+ from tryptophan. The enzyme is also known by several synonyms, including QAPRTase, quinolinic acid phosphoribosyltransferase, and nicotinate-nucleotide pyrophosphorylase (carboxylating).
Why Is nicotinate-nucleotide diphosphorylase (carboxylating) activity Important in Cell Biology?
GO:0004514 is important because it represents a critical enzymatic step in the de novo NAD+ biosynthesis pathway, which is essential for maintaining cellular NAD+ levels and supporting processes such as energy metabolism, DNA repair, and immune function. Dysregulation of this activity has been linked to aging, inflammation, acute kidney injury, and neurodegenerative conditions, making it a potential target for therapeutic intervention. Understanding how this activity is regulated and how it contributes to disease can inform the development of strategies to modulate NAD+ metabolism.
• Maintains cellular NAD+ pools for energy metabolism and signaling.
• Influences immune function in aging and inflammation.
• Protects against acute kidney injury through HNF4α-mediated expression.
• Implicated in neurodegenerative conditions via quinolinic acid production.
• Regulated by cellular stress, which can impair NAD+ biosynthesis.
• Tissue-specific expression patterns suggest specialized roles in kidney, liver, and brain.
• Potential target for modulating NAD+ levels in age-related diseases.
• Enzyme activity can be inhibited by endogenous factors in lung tissue.
• Peroxisome proliferators can affect the TRP-NAD pathway, including this activity.
• Provides a metabolic link between tryptophan catabolism and NAD+ synthesis.
Molecular Mechanism of nicotinate-nucleotide diphosphorylase (carboxylating) activity
Substrate Binding and Decarboxylation
In simple terms: The enzyme grabs nicotinate D-ribonucleotide and removes a carboxyl group, setting the stage for the reaction.
The enzyme binds nicotinate D-ribonucleotide and catalyzes the decarboxylation of the substrate, releasing CO2. This step is essential for the formation of quinolinate, the product of the reaction. The reaction is reversible, and the enzyme can also catalyze the reverse reaction, incorporating CO2 into quinolinate to form nicotinate D-ribonucleotide.
Phosphoribosyl Transfer
In simple terms: The enzyme transfers a phosphoribosyl group from diphosphate to the substrate, completing the reaction.
Following decarboxylation, the enzyme transfers a phosphoribosyl group from diphosphate to the substrate, yielding 5-phospho-alpha-D-ribose 1-diphosphate and quinolinate. This transfer is a key step in the de novo NAD+ pathway, as it generates a precursor for subsequent NAD+ synthesis.
Reaction Reversibility and Equilibrium
In simple terms: The enzyme can work in both directions, depending on what the cell needs.
The reaction catalyzed by GO:0004514 is reversible, and the direction depends on substrate availability and cellular conditions. In the forward direction, it produces quinolinate, which is then converted to nicotinate mononucleotide for NAD+ synthesis. In the reverse direction, it can salvage nicotinate D-ribonucleotide.
Regulation by Cellular Stress
In simple terms: When cells are stressed, this enzyme's activity can be reduced, affecting NAD+ production.
Cellular stress responses can impair de novo NAD+ biosynthesis by downregulating the activity of enzymes in the pathway, including GO:0004514. This has been observed in kidney cells under stress conditions, where reduced QPRT expression leads to decreased NAD+ levels.
Tissue-Specific Isoforms and Expression
In simple terms: Different tissues express this enzyme at different levels, tailored to their needs.
The enzyme is encoded by the QPRT gene, and its expression varies across tissues. High levels are found in kidney, liver, and brain, where NAD+ demand is high. This tissue-specific expression is regulated by transcription factors such as HNF4α in the kidney.
Key Genes Involved in GO:0004514 nicotinate-nucleotide diphosphorylase (carboxylating) activity
The following genes are directly or indirectly involved in the nicotinate-nucleotide diphosphorylase (carboxylating) activity and its associated NAD+ biosynthesis pathway.
| Gene | Major Role | Research Relevance |
|---|---|---|
| QPRT | Encodes the enzyme with GO:0004514 activity; catalyzes the key step in de novo NAD+ synthesis | Central to studies of NAD+ metabolism, kidney injury, and neuroprotection |
| HNF4A | Transcription factor that regulates QPRT expression in kidney | Modulates resilience to acute kidney injury |
| IDO1 | Rate-limiting enzyme in tryptophan catabolism, upstream of QPRT | Links immune regulation and NAD+ synthesis |
| TDO2 | Tryptophan 2,3-dioxygenase, alternative upstream enzyme | Tissue-specific regulation of tryptophan flux |
| KYNU | Kynureninase, involved in tryptophan catabolism to quinolinate | Provides substrate for QPRT |
| HAAO | 3-hydroxyanthranilate 3,4-dioxygenase, produces quinolinate | Upstream of QPRT in NAD+ pathway |
| NADSYN1 | NAD synthetase, downstream of QPRT | Converts nicotinate mononucleotide to NAD+ |
| NMNAT1 | Nicotinamide mononucleotide adenylyltransferase, salvage pathway | Alternative NAD+ synthesis route |
| NAMPT | Nicotinamide phosphoribosyltransferase, salvage pathway | Regulates NAD+ levels independently of QPRT |
| SIRT1 | NAD+-dependent deacetylase | Senses NAD+ levels influenced by QPRT activity |
| PARP1 | NAD+-consuming enzyme in DNA repair | Links NAD+ availability to genome stability |
| ACMSD | Aminocarboxymuconate semialdehyde decarboxylase | Diverts tryptophan away from NAD+ synthesis |
| CCBL1 | Kynurenine aminotransferase, alternative branch | Competes with NAD+ pathway |
| GAPDH | Glycolytic enzyme, NAD+ dependent | Affected by NAD+ levels |
| SIRT3 | Mitochondrial NAD+-dependent deacetylase | Mitochondrial NAD+ sensing |
| NRK1 | Nicotinamide riboside kinase, salvage pathway | Alternative NAD+ precursor |
| NMRK2 | Nicotinamide riboside kinase 2 | Tissue-specific NAD+ salvage |
How Is nicotinate-nucleotide diphosphorylase (carboxylating) activity Regulated?
The activity of GO:0004514 is regulated at multiple levels. Transcriptionally, QPRT expression is controlled by tissue-specific transcription factors such as HNF4α in the kidney, which enhances QPRT expression and supports NAD+ biosynthesis under stress conditions. Cellular stress responses can downregulate QPRT and impair de novo NAD+ biosynthesis, as observed in kidney cells. Additionally, endogenous inhibitors of the enzyme have been identified in lung tissue, suggesting tissue-specific regulation. Peroxisome proliferators can also affect the TRP-NAD pathway, potentially influencing QPRT activity. These regulatory mechanisms ensure that NAD+ synthesis is matched to cellular demand and can be rapidly adjusted in response to physiological cues.
nicotinate-nucleotide diphosphorylase (carboxylating) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| QPRT | Acute kidney injury; aging; inflammation | Kidney-specific Qprt knockout mouse; CRISPR KO in HK-2 cells |
| HNF4A | Acute kidney injury | HNF4A knockout or knockdown in kidney organoids |
| IDO1 | Immune dysfunction in aging | Ido1 knockout macrophages; CRISPR KO in primary macrophages |
| QPRT | Neurodegeneration (quinolinic acid toxicity) | Neuron-specific Qprt knockout; overexpression in neuronal cultures |
| QPRT | NAD+ deficiency disorders | Patient-derived iPSCs with QPRT mutations; CRISPR correction |
Acute Kidney Injury
QPRT-mediated NAD+ biosynthesis is critical for kidney resilience. HNF4α regulates QPRT expression, and loss of this regulation exacerbates acute kidney injury in experimental models. Cellular stress impairs de novo NAD+ biosynthesis in the kidney, contributing to injury.
Aging and Inflammation
Macrophage de novo NAD+ synthesis, which depends on QPRT activity, specifies immune function in aging and inflammation. Reduced NAD+ levels in aging macrophages impair their function, linking GO:0004514 to immunosenescence.
Neurodegeneration
Quinolinic acid, the product of the reverse reaction, is a neurotoxin implicated in neurodegenerative diseases. QAPRTase activity in the brain regulates quinolinic acid levels, and dysregulation may contribute to neuroinflammation and excitotoxicity.
From nicotinate-nucleotide diphosphorylase (carboxylating) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does QPRT loss affect NAD+ levels and kidney function? | Qprt knockout mouse or CRISPR KO in kidney cell lines |
| How does HNF4α regulate QPRT expression? | HNF4A knockout or point mutation in kidney cells |
| What is the effect of QPRT overexpression on NAD+ and stress resistance? | QPRT overexpression in cell lines or mouse models |
| Can a point mutation in QPRT alter its enzymatic activity? | CRISPR point mutation knock-in in QPRT locus |
| How does QPRT activity affect immune cell function? | Conditional Qprt knockout in macrophages |
| What is the role of QPRT in neuronal survival? | Neuron-specific Qprt knockout or overexpression |
How to Study the nicotinate-nucleotide diphosphorylase (carboxylating) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay (HPLC) | QAPRTase activity | Kinetic studies, inhibitor screening |
| Stable isotope tracing | Metabolic flux through NAD+ pathway | Quantifying de novo NAD+ synthesis |
| RNA-seq | QPRT mRNA expression | Tissue-specific expression, stress response |
| ChIP-seq | Transcription factor binding to QPRT promoter | Identifying HNF4α regulation |
| CRISPR knockout | Loss-of-function phenotype | Kidney injury models, immune function |
| CRISPR knock-in | Tagged or mutant QPRT | Localization, activity studies |
| Proteomics | QPRT protein levels and interactions | Pathway analysis |
| Metabolomics | NAD+ and intermediates | Assessing pathway activity |
Enzymatic Activity Assays
Direct measurement of QAPRTase activity using radiolabeled substrates or HPLC-based detection of quinolinate and nicotinate D-ribonucleotide. These assays can be performed on cell lysates or purified enzyme and are useful for kinetic studies and inhibitor screening.
Metabolic Flux Analysis
Stable isotope tracing with labeled tryptophan or nicotinate can quantify flux through the de novo NAD+ pathway, revealing how QPRT activity contributes to NAD+ pools under different conditions.
Gene Expression Analysis
RNA-seq and qPCR can measure QPRT mRNA levels across tissues and conditions. This is complemented by ChIP-seq to identify transcription factor binding sites, such as HNF4α, in the QPRT promoter.
CRISPR-Based Genetic Models
Knockout, knock-in, and point mutation models generated via CRISPR/Cas9 allow precise dissection of QPRT function in cells and animals. These models are essential for linking GO:0004514 activity to physiological outcomes.
How CRISPR Can Be Used to Study GO:0004514 nicotinate-nucleotide diphosphorylase (carboxylating) activity
Knockout
CRISPR/Cas9-mediated knockout of QPRT eliminates GO:0004514 activity, allowing researchers to study the consequences of NAD+ depletion in cells and animal models. This approach has been used to demonstrate the importance of QPRT in kidney resilience and macrophage function.
Point Mutation
Introducing specific point mutations in the QPRT catalytic domain can dissect the enzymatic mechanism and identify residues critical for substrate binding or catalysis. Such models are valuable for understanding how mutations affect NAD+ synthesis.
Knock-in
Knock-in of tagged QPRT (e.g., FLAG or GFP) enables visualization and immunoprecipitation of the enzyme, facilitating studies of its localization, interactions, and post-translational modifications.
Overexpression
Overexpression of QPRT via CRISPR activation or lentiviral delivery can boost NAD+ levels and protect against stress. This approach is used to test whether enhancing GO:0004514 activity is beneficial in disease models.
How EDITGENE Supports nicotinate-nucleotide diphosphorylase (carboxylating) activity Research
Researchers studying nicotinate-nucleotide diphosphorylase (carboxylating) activity-related genes often need to determine whether a candidate gene is causally involved in NAD+ metabolism, stress resistance, or disease progression. 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 nicotinate-nucleotide diphosphorylase (carboxylating) activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| QPRT Knockout HEK293 Cell Line | EDJ-KQ51109 | Human | 23475 | Details Get a Quote |
| QPRT Knockout HeLa Cell Line | EDJ-KQ55747 | Human | 23475 | Details Get a Quote |
| QPRT Knockout A-549 Cell Line | EDJ-KQ64245 | Human | 23475 | Details Get a Quote |
| QPRT Knockout HCT 116 Cell Line | EDJ-KQ72691 | Human | 23475 | Details Get a Quote |
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Frequently Asked Questions About nicotinate-nucleotide diphosphorylase (carboxylating) activity
What is GO:0004514?
GO:0004514 is the Gene Ontology term for nicotinate-nucleotide diphosphorylase (carboxylating) activity, an enzymatic function that catalyzes a key step in de novo NAD+ biosynthesis from tryptophan.
What genes are involved in nicotinate-nucleotide diphosphorylase (carboxylating) activity?
The primary gene is QPRT, which encodes the enzyme. Other genes in the pathway include IDO1, KYNU, HAAO, and NADSYN1.
What is the function of QPRT?
QPRT encodes the enzyme with GO:0004514 activity, which converts nicotinate D-ribonucleotide to quinolinate, a precursor for NAD+ synthesis.
How is QPRT regulated?
QPRT is regulated transcriptionally by factors such as HNF4α in the kidney, and its activity can be impaired by cellular stress.
What diseases are associated with QPRT dysfunction?
QPRT dysfunction has been linked to acute kidney injury, aging-related immune dysfunction, and neurodegeneration.
How can I study GO:0004514 activity in the lab?
You can use enzymatic assays, metabolic flux analysis, and CRISPR-based genetic models to study this activity.
What is the reaction catalyzed by QAPRTase?
QAPRTase catalyzes the reversible conversion of nicotinate D-ribonucleotide, CO2, and diphosphate to quinolinate and 5-phospho-alpha-D-ribose 1-diphosphate.
Is QPRT the same as QAPRTase?
Yes, QPRT is the gene name, and QAPRTase is a common name for the enzyme it encodes.
What tissues express QPRT highly?
QPRT is highly expressed in kidney, liver, and brain.
Can CRISPR be used to study QPRT function?
Yes, CRISPR knockout, knock-in, and point mutation models are powerful tools to dissect QPRT function in cells and animals.
Conclusion
GO:0004514, nicotinate-nucleotide diphosphorylase (carboxylating) activity, is a central enzymatic function in de novo NAD+ biosynthesis with far-reaching implications for cellular metabolism, immune function, and disease. Understanding its regulation and role in pathologies such as acute kidney injury and neurodegeneration requires robust experimental models. EDITGENE offers a comprehensive suite of CRISPR services to facilitate functional studies of QPRT and related genes, empowering researchers to uncover new therapeutic strategies targeting NAD+ metabolism.
References
- 1. Minhas PS et al.. 2019. Macrophage de novo NAD(+) synthesis specifies immune function in aging and inflammation.. Nat Immunol 20(1):50-63 PMID: 30478397
- 2. Ruggieri S et al.. 2015. Regulation of NAD biosynthetic enzymes modulates NAD-sensing processes to shape mammalian cell physiology under varying biological cues.. Biochim Biophys Acta 1854(9):1138-49 PMID: 25770681
- 3. Bignon Y et al.. 2022. Cell stress response impairs de novo NAD+ biosynthesis in the kidney.. JCI Insight 7(1) PMID: 34793337
- 4. Shibata K. 2018. Organ Co-Relationship in Tryptophan Metabolism and Factors That Govern the Biosynthesis of Nicotinamide from Tryptophan.. J Nutr Sci Vitaminol (Tokyo) 64(2):90-98 PMID: 29710037
- 5. Foster AC et al.. 1985. Quinolinic acid phosphoribosyltransferase in rat brain.. J Neurochem 44(2):446-54 PMID: 2578178
- 6. Seither RL et al.. 1991. Lung contains an inhibitor for nicotinatemononucleotide pyrophosphorylase (carboxylating) of NAD biosynthesis.. Life Sci 48(3):253-9 PMID: 1992282
- 7. Clark AJ et al.. 2023. Hepatocyte nuclear factor 4α mediated quinolinate phosphoribosylltransferase (QPRT) expression in the kidney facilitates resilience against acute kidney injury.. Kidney Int 104(6):1150-1163 PMID: 37783445
- 8. Shin M et al.. 1999. Effects of peroxisome-proliferators on the TRP-NAD pathway.. Adv Exp Med Biol 467:333-40 PMID: 10721074
