GO:0034354 'de novo' NAD+ biosynthetic process from L-tryptophan: Kynurenine Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034354 describes the metabolic route that converts L-tryptophan into nicotinamide adenine dinucleotide (NAD+) through the kynurenine pathway, a de novo route distinct from salvage and Preiss-Handler pathways.
• The pathway is a major source of NAD+ in the liver, kidney, and immune cells, and its impairment is linked to acute kidney injury, metabolic dysfunction-associated steatotic liver disease (MASLD/MASH), inflammatory bowel disease, polycystic ovary syndrome, and aging-related inflammation.
• Key enzymes include TDO2, IDO1, IDO2, KMO, KYNU, ACMSD, QPRT, and the terminal enzyme NMNAT, which together channel tryptophan-derived intermediates into NAD+.
• ACMSD acts as a critical gatekeeper: its inhibition shunts intermediates toward NAD+ synthesis and has been shown to correct fibrosis, inflammation, and DNA damage in MASLD/MASH models.
• Macrophage de novo NAD+ synthesis is required for proper immune function, and its decline during aging and inflammation contributes to immune dysfunction.
• CRISPR knockout, point-mutation, knock-in, and overexpression models of pathway genes enable causal dissection of GO:0034354 in disease and immunity.
Description
GO:0034354, 'de novo' NAD+ biosynthetic process from L-tryptophan, is a biological process that converts the essential amino acid L-tryptophan into nicotinamide adenine dinucleotide (NAD+) via the kynurenine pathway. NAD+ is a redox cofactor and substrate for signaling enzymes such as sirtuins and PARPs, and its de novo synthesis from tryptophan represents one of the three principal routes of NAD+ production, alongside the salvage pathway and the Preiss-Handler pathway. Unlike salvage, which recycles nicotinamide, this de novo route depends on dietary tryptophan and a sequential enzymatic cascade that includes tryptophan 2,3-dioxygenase (TDO2), indoleamine 2,3-dioxygenase (IDO1/IDO2), kynurenine 3-monooxygenase (KMO), kynureninase (KYNU), 2-amino-3-carboxymuconate-6-semialdehyde decarboxylase (ACMSD), quinolinate phosphoribosyltransferase (QPRT), and nicotinamide mononucleotide adenylyltransferase (NMNAT). The pathway is especially important in the liver and kidney, where it contributes substantially to systemic NAD+ pools, and in immune cells, where it shapes inflammatory responses. Impairment of de novo NAD+ synthesis has been documented in human acute kidney injury, where urinary quinolinate and related metabolites correlate with disease severity. In macrophages, de novo NAD+ synthesis specifies immune function and declines with aging and inflammation, linking this metabolic route to immunometabolism. More recently, disruption of gut microbiota-mediated de novo NAD+ synthesis has been implicated in polycystic ovary syndrome, and a metabolic constraint in the kynurenine pathway drives mucosal inflammation in inflammatory bowel disease. For researchers, GO:0034354 provides a defined ontology node to annotate genes, interpret metabolomic and transcriptomic data, and design mechanistic experiments. Because the pathway intersects with amino-acid sensing, immune regulation, and metabolic stress, it is a fertile area for CRISPR-based functional genomics.
'de novo' NAD+ biosynthetic process from L-tryptophan At A Glance
| GO ID | GO:0034354 |
|---|---|
| GO term | 'de novo' NAD+ biosynthetic process from L-tryptophan |
| Ontology | biological_process |
| Synonym | None listed in QuickGO |
| Major function | Conversion of L-tryptophan to NAD+ via the kynurenine pathway |
| Key substrates | L-tryptophan, kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilate, ACMS, quinolinate |
| Key enzymes | TDO2, IDO1, IDO2, KMO, KYNU, ACMSD, QPRT, NMNAT |
| Tissue relevance | Liver, kidney, immune cells, gut, ovary |
| Disease links | Acute kidney injury, MASLD/MASH, IBD, PCOS, aging-related inflammation |
What Is GO:0034354?
GO:0034354 is the biological process in which L-tryptophan is enzymatically converted through the kynurenine pathway to produce NAD+ de novo, without recycling preformed nicotinamide or nicotinic acid. The process begins with tryptophan oxidation by TDO2 or IDO1/IDO2, proceeds through kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilate, and 2-amino-3-carboxymuconate-6-semialdehyde (ACMS), and ends with quinolinate conversion to NAD+ via QPRT and NMNAT. It is distinct from the salvage pathway and the Preiss-Handler pathway, which use nicotinamide and nicotinic acid respectively.
Why Is 'de novo' NAD+ biosynthetic process from L-tryptophan Important in Cell Biology?
GO:0034354 is important because it defines a metabolic route that sustains NAD+ pools critical for redox balance, DNA repair, and immune function, and its dysregulation is causally implicated in human diseases including acute kidney injury, MASLD/MASH, inflammatory bowel disease, polycystic ovary syndrome, and aging-related inflammation. Understanding this pathway provides mechanistic insight into how tryptophan availability, enzyme activity, and metabolic stress converge on NAD+ homeostasis, and it offers therapeutic entry points such as ACMSD inhibition.
• Provides a de novo source of NAD+ independent of salvage and Preiss-Handler pathways.
• Supports macrophage immune function and is required for proper inflammatory responses.
• Its impairment is associated with human acute kidney injury severity.
• ACMSD inhibition corrects fibrosis, inflammation, and DNA damage in MASLD/MASH models.
• Disruption of gut microbiota-mediated de novo NAD+ synthesis contributes to polycystic ovary syndrome.
• A metabolic constraint in the kynurenine pathway drives mucosal inflammation in IBD.
• Links amino-acid sensing and degrading pathways to immune regulation.
• NAD+ metabolism is intertwined with metabolic stress and infection responses.
• Serves as a target for CRISPR functional genomics to identify causal genes.
• Enables metabolomic and transcriptomic annotation of kynurenine pathway activity.
What Happens During 'de novo' NAD+ biosynthetic process from L-tryptophan?
Step 1: Tryptophan oxidation to kynurenine
In simple terms: The pathway starts when tryptophan is converted into kynurenine.
L-tryptophan is oxidized to N-formylkynurenine by TDO2 in the liver or by IDO1/IDO2 in immune and other tissues, and N-formylkynurenine is rapidly converted to kynurenine. This step commits tryptophan to the kynurenine pathway and is a key regulatory node influenced by amino-acid sensing and immune signals.
Step 2: Kynurenine to 3-hydroxykynurenine and 3-hydroxyanthranilate
In simple terms: Kynurenine is modified in two steps to make a reactive intermediate.
Kynurenine is hydroxylated by KMO to 3-hydroxykynurenine, which is then cleaved by KYNU to 3-hydroxyanthranilate. These reactions channel intermediates toward the NAD+ branch and are sensitive to metabolic constraints that can divert flux in inflammatory conditions.
Step 3: ACMSD gate and quinolinate formation
In simple terms: A gatekeeper enzyme decides whether the intermediate becomes NAD+ or is burned off.
3-Hydroxyanthranilate is converted to 2-amino-3-carboxymuconate-6-semialdehyde (ACMS), which can either be decarboxylated by ACMSD or spontaneously cyclize to quinolinate. ACMSD inhibition shunts ACMS toward quinolinate and NAD+ synthesis, and has been shown to correct fibrosis, inflammation, and DNA damage in MASLD/MASH models.
Step 4: Quinolinate to NAD+ via QPRT and NMNAT
In simple terms: The final steps build NAD+ from quinolinate.
Quinolinate is converted by QPRT to nicotinate mononucleotide, which is then adenylylated by NMNAT to form NAD+. This terminal segment is shared conceptually with other NAD+ biosynthetic routes and is essential for maintaining cellular NAD+ pools.
Step 5: Pathway integration with immune and metabolic signaling
In simple terms: The pathway does not work alone; it talks to immune and metabolic signals.
De novo NAD+ synthesis from tryptophan is integrated with amino-acid sensing and immune regulation, and macrophage de novo NAD+ synthesis specifies immune function in aging and inflammation. Disruption of gut microbiota-mediated de novo NAD+ synthesis contributes to polycystic ovary syndrome, and a metabolic constraint in the kynurenine pathway drives mucosal inflammation in IBD.
Key Genes Involved in GO:0034354 'de novo' NAD+ biosynthetic process from L-tryptophan
The following genes and enzymes are central to GO:0034354 and are frequently studied using CRISPR-based models.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TDO2 | Oxidizes L-tryptophan to N-formylkynurenine in liver | Liver NAD+ synthesis and systemic tryptophan catabolism |
| IDO1 | Oxidizes L-tryptophan in immune and other tissues | Immune regulation and inflammation |
| IDO2 | Tryptophan-catabolizing enzyme with immune roles | Immune tolerance and NAD+ synthesis |
| KMO | Hydroxylates kynurenine to 3-hydroxykynurenine | Flux control and neuroactive metabolite balance |
| KYNU | Cleaves 3-hydroxykynurenine to 3-hydroxyanthranilate | Kynurenine pathway flux and inflammation |
| ACMSD | Decarboxylates ACMS, gating NAD+ synthesis | Therapeutic target in MASLD/MASH |
| QPRT | Converts quinolinate to nicotinate mononucleotide | Terminal NAD+ synthesis step |
| NMNAT1 | Adenylylates nicotinate mononucleotide to NAD+ | NAD+ biosynthesis and cellular redox |
| NMNAT2 | NAD+ synthesis in neurons | Neuronal NAD+ homeostasis |
| NMNAT3 | Mitochondrial NAD+ synthesis | Mitochondrial metabolism |
| SLC7A5 | Amino-acid transporter influencing tryptophan availability | Amino-acid sensing and immune regulation |
| SLC7A11 | Cystine/glutamate transporter linked to metabolic stress | Metabolic stress and infection |
| SIRT1 | NAD+-dependent deacetylase | NAD+ sensor and metabolic regulation |
| PARP1 | NAD+-consuming DNA repair enzyme | DNA damage and NAD+ demand |
| NAMPT | Salvage pathway enzyme, context for de novo route | NAD+ homeostasis comparison |
| QPRT | Quinolinate phosphoribosyltransferase | NAD+ synthesis and neurotoxicity |
| ACMSD | Gatekeeper of the kynurenine pathway | CRISPR target for NAD+ modulation |
How Is 'de novo' NAD+ biosynthetic process from L-tryptophan Regulated?
GO:0034354 is regulated at multiple levels. Enzyme expression of TDO2 and IDO1 is influenced by amino-acid sensing and immune signals, linking tryptophan availability to pathway flux. ACMSD acts as a metabolic gatekeeper, and its inhibition redirects intermediates toward NAD+ synthesis, correcting fibrosis, inflammation, and DNA damage in MASLD/MASH models. Macrophage de novo NAD+ synthesis is specified by immune state and declines with aging and inflammation, indicating regulation by inflammatory cues. Metabolic constraints in the kynurenine pathway can drive mucosal inflammation in IBD, suggesting that flux limitation is a regulatory mechanism. NAD+ metabolism overall is responsive to metabolic stress and infection, which further modulates pathway activity.
'de novo' NAD+ biosynthetic process from L-tryptophan and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ACMSD | MASLD/MASH fibrosis and inflammation | ACMSD knockout or inhibitor-treated hepatocytes |
| IDO1 | Immune regulation and inflammation | IDO1 knockout macrophages |
| QPRT | Acute kidney injury and NAD+ depletion | QPRT knockout kidney cells |
| KYNU | Inflammatory bowel disease mucosal inflammation | KYNU knockout intestinal organoids |
| NMNAT | NAD+ homeostasis in aging and PCOS | NMNAT overexpression in ovarian cells |
Acute kidney injury
De novo NAD+ biosynthetic impairment has been documented in acute kidney injury in humans, where urinary quinolinate and related metabolites correlate with disease severity. This links GO:0034354 directly to a clinically relevant renal phenotype and supports the pathway as a biomarker and therapeutic target.
MASLD/MASH and liver fibrosis
ACMSD inhibition corrects fibrosis, inflammation, and DNA damage in MASLD/MASH, demonstrating that modulating the kynurenine pathway gate can restore NAD+ synthesis and ameliorate liver disease. This positions GO:0034354 as a central node in metabolic liver disease.
Inflammatory bowel disease
A metabolic constraint in the kynurenine pathway drives mucosal inflammation in IBD, indicating that impaired de novo NAD+ synthesis contributes to intestinal inflammation. This connects GO:0034354 to mucosal immunometabolism.
Polycystic ovary syndrome and aging-related inflammation
Disruption of gut microbiota-mediated de novo NAD+ synthesis contributes to polycystic ovary syndrome, and macrophage de novo NAD+ synthesis specifies immune function in aging and inflammation. These findings broaden the disease relevance of GO:0034354 to reproductive and aging-related conditions.
From 'de novo' NAD+ biosynthetic process from L-tryptophan-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ACMSD alter NAD+ levels and fibrosis? | ACMSD knockout hepatocytes or mice |
| Is IDO1 required for macrophage immune function? | IDO1 knockout macrophages |
| Does QPRT deficiency impair kidney NAD+ synthesis? | QPRT knockout kidney cells |
| Does KYNU constraint drive mucosal inflammation? | KYNU knockout intestinal organoids |
| Does NMNAT overexpression rescue NAD+ depletion? | NMNAT knock-in or overexpression cells |
| Does gut microbiota-mediated NAD+ synthesis affect PCOS? | Germ-free or antibiotic-treated models |
How to Study the 'de novo' NAD+ biosynthetic process from L-tryptophan Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Targeted metabolomics | Tryptophan, kynurenine, quinolinate, NAD+ levels | Pathway flux in disease models |
| RNA-seq | Expression of TDO2, IDO1, KMO, KYNU, ACMSD, QPRT | Transcriptional regulation |
| Western blot | Protein levels of pathway enzymes | Enzyme abundance |
| Enzyme activity assay | ACMSD, QPRT, NMNAT catalytic activity | Functional validation |
| CRISPR knockout screen | Gene essentiality for NAD+ synthesis | Causal gene discovery |
| Isotope tracing | Flux through kynurenine pathway | Metabolic flux analysis |
| NAD+ quantification | Cellular NAD+ pools | Pathway output |
| Immunofluorescence | Enzyme localization in tissues | Tissue-specific pathway activity |
Metabolomics and flux analysis
Targeted metabolomics of tryptophan, kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilate, quinolinate, and NAD+ quantifies pathway activity and identifies bottlenecks in GO:0034354. Isotope tracing can further resolve flux through the kynurenine pathway.
Transcriptomics and RNA-seq
RNA-seq of pathway enzymes such as TDO2, IDO1, KMO, KYNU, ACMSD, and QPRT reveals transcriptional regulation of GO:0034354 in disease models and immune cells.
Proteomics and enzyme activity assays
Western blotting and enzymatic activity assays for ACMSD, QPRT, and NMNAT measure protein abundance and catalytic capacity, complementing metabolomic readouts.
CRISPR functional genomics
Pooled CRISPR knockout screens targeting kynurenine pathway genes can identify causal regulators of NAD+ synthesis and disease phenotypes.
How CRISPR Can Be Used to Study GO:0034354 'de novo' NAD+ biosynthetic process from L-tryptophan
Knockout
CRISPR knockout of ACMSD, IDO1, QPRT, or KYNU enables loss-of-function studies to determine whether these genes are required for de novo NAD+ synthesis and disease phenotypes. Knockout models are particularly useful for testing causal roles in MASLD/MASH, acute kidney injury, and IBD.
Point Mutation
Point mutations can be introduced into catalytic residues of ACMSD, QPRT, or NMNAT to dissect enzymatic mechanisms and separate catalytic from non-catalytic functions in GO:0034354.
Knock-in
Knock-in of tagged or fluorescent versions of pathway enzymes allows tracking of protein localization, interaction, and turnover in live cells, providing spatial and dynamic information about the kynurenine pathway.
Overexpression
Overexpression of ACMSD, QPRT, or NMNAT can test whether increasing pathway flux raises NAD+ levels and rescues disease phenotypes, complementing loss-of-function approaches.
How EDITGENE Supports 'de novo' NAD+ biosynthetic process from L-tryptophan Research
Researchers studying 'de novo' NAD+ biosynthetic process from L-tryptophan-related genes often need to determine whether a candidate gene is causally involved in NAD+ homeostasis, immune regulation, or disease phenotypes. EDITGENE provides CRISPR-based cell models and screening services to accelerate this causal dissection.
Contact EDITGENE today to design your custom CRISPR model for 'de novo' NAD+ biosynthetic process from L-tryptophan research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| IDO1 Knockout HEK293 Cell Line | EDJ-KQ1085 | Human | 3620 | Details Get a Quote |
| IDO2 Knockout HEK293 Cell Line | EDJ-KQ2939 | Human | 169355 | Details Get a Quote |
| KMO Knockout HEK293 Cell Line | EDJ-KQ6289 | Human | 8564 | Details Get a Quote |
| KYNU Knockout HEK293 Cell Line | EDJ-KQ6412 | Human | 8942 | Details Get a Quote |
| NMNAT2 Knockout HEK293 Cell Line | EDJ-KQ7802 | Human | 23057 | Details Get a Quote |
| HAAO Knockout HEK293 Cell Line | EDJ-KQ8031 | Human | 23498 | Details Get a Quote |
| AFMID Knockout HEK293 Cell Line | EDJ-KQ8718 | Human | 125061 | Details Get a Quote |
| NADSYN1 Knockout HEK293 Cell Line | EDJ-KQ14364 | Human | 55191 | Details Get a Quote |
| AFMID Knockout A-549 Cell Line | EDJ-KQ34944 | Human | 125061 | Details Get a Quote |
| AFMID Knockout HCT 116 Cell Line | EDJ-KQ34945 | Human | 125061 | Details Get a Quote |
| AFMID Knockout HeLa Cell Line | EDJ-KQ34946 | Human | 125061 | Details Get a Quote |
| NADSYN1 Knockout A-549 Cell Line | EDJ-KQ44497 | Human | 55191 | Details Get a Quote |
| NADSYN1 Knockout HCT 116 Cell Line | EDJ-KQ44498 | Human | 55191 | Details Get a Quote |
| NADSYN1 Knockout HeLa Cell Line | EDJ-KQ44499 | Human | 55191 | Details Get a Quote |
| KYNU Knockout A-549 Cell Line | EDJ-KQ30452 | Human | 8942 | Details Get a Quote |
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Frequently Asked Questions About 'de novo' NAD+ biosynthetic process from L-tryptophan
What is GO:0034354?
GO:0034354 is the biological process that converts L-tryptophan to NAD+ via the kynurenine pathway, representing a de novo route of NAD+ synthesis.
What genes are involved in 'de novo' NAD+ biosynthetic process from L-tryptophan?
Key genes include TDO2, IDO1, IDO2, KMO, KYNU, ACMSD, QPRT, and NMNAT.
Why is de novo NAD+ synthesis from tryptophan important?
It sustains NAD+ pools for redox balance, DNA repair, and immune function, and its impairment is linked to kidney injury, liver disease, IBD, PCOS, and aging-related inflammation.
How is de novo NAD+ synthesis from tryptophan regulated?
It is regulated by enzyme expression, amino-acid sensing, ACMSD gatekeeping, and inflammatory cues.
What diseases are associated with impaired de novo NAD+ synthesis?
Acute kidney injury, MASLD/MASH, inflammatory bowel disease, polycystic ovary syndrome, and aging-related inflammation.
What is the role of ACMSD in this pathway?
ACMSD decarboxylates ACMS and acts as a gatekeeper; its inhibition redirects flux toward NAD+ synthesis and corrects fibrosis and inflammation in MASLD/MASH models.
How can CRISPR be used to study GO:0034354?
CRISPR knockout, point mutation, knock-in, and overexpression models can test causal roles of pathway genes in NAD+ synthesis and disease.
What methods measure de novo NAD+ synthesis?
Targeted metabolomics, isotope tracing, RNA-seq, enzyme activity assays, and NAD+ quantification.
Is de novo NAD+ synthesis from tryptophan linked to immune function?
Yes, macrophage de novo NAD+ synthesis specifies immune function in aging and inflammation.
What experimental models are suitable for studying this pathway?
Knockout and overexpression cell lines, organoids, and animal models targeting ACMSD, IDO1, QPRT, KYNU, and NMNAT.
Conclusion
GO:0034354, 'de novo' NAD+ biosynthetic process from L-tryptophan, is a central metabolic route that links tryptophan catabolism to NAD+ homeostasis, immune function, and disease. Its dysregulation is implicated in acute kidney injury, MASLD/MASH, IBD, PCOS, and aging-related inflammation, and key enzymes such as ACMSD, IDO1, QPRT, and NMNAT are actionable targets. CRISPR-based knockout, point-mutation, knock-in, and overexpression models provide powerful tools to dissect causality and develop therapeutic strategies.
References
- 1. Liu YJ et al.. 2025. ACMSD inhibition corrects fibrosis, inflammation, and DNA damage in MASLD/MASH.. J Hepatol 82(2):174-188 PMID: 39181211
- 2. 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
- 3. Poyan Mehr A et al.. 2018. De novo NAD(+) biosynthetic impairment in acute kidney injury in humans.. Nat Med 24(9):1351-1359 PMID: 30127395
- 5. Chen K et al.. 2025. Disruption of Gut Microbiota-Mediated De Novo NAD(+) Synthesis Contributes to the Development of Polycystic Ovary Syndrome.. Adv Sci (Weinh) 12(45):e06497 PMID: 41082373
- 6. Welz L et al.. 2024. A metabolic constraint in the kynurenine pathway drives mucosal inflammation in IBD.. medRxiv PMID: 39211892
- 7. Groth B et al.. 2021. NAD(+) Metabolism, Metabolic Stress, and Infection.. Front Mol Biosci 8:686412 PMID: 34095234
- 8. Grohmann U et al.. 2017. Amino-acid sensing and degrading pathways in immune regulation.. Cytokine Growth Factor Rev 35:37-45 PMID: 28545736
