GO:0160047 muramyl dipeptide kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0160047 (muramyl dipeptide kinase activity) catalyzes the ATP-dependent phosphorylation of muramyl dipeptide (MDP) to 6-O-phospho-MDP, producing ADP and H+.
• The enzyme responsible for this activity in humans is N-acetylglucosamine kinase (NAGK), which phosphorylates MDP and is required for NOD2 activation.
• Phosphorylated MDP is the bioactive ligand that binds NOD2, triggering innate immune signaling and downstream inflammatory responses [4,5].
• Dysregulation of this pathway is linked to inflammatory bowel diseases, colorectal cancer, and other inflammatory disorders [1,3,5,8].
• Key genes in the pathway include NAGK, NOD2, RIPK2, and downstream effectors such as YAP and DUBA, which modulate signaling strength and duration [3,4,7].
• Experimental approaches to study this activity include kinase assays, CRISPR knockout/knock-in models, and phenotypic screens in immune and cancer cell lines [4,7].
Description
Muramyl dipeptide kinase activity (GO:0160047) is a molecular function that catalyzes the transfer of a phosphate group from ATP to muramyl dipeptide (MDP), yielding ADP, a proton, and 6-O-phospho-MDP. This modification is critical for converting MDP, a bacterial cell wall fragment, into a potent activator of the innate immune receptor NOD2 [4,5]. The discovery that NAGK (N-acetylglucosamine kinase) performs this phosphorylation established a direct link between bacterial metabolite sensing and host immune activation. Researchers study this activity because it sits at the interface of microbial sensing and inflammatory signaling. Phosphorylated MDP is the specific ligand that binds NOD2, initiating a signaling cascade that involves RIPK2 and downstream effectors, which together shape immune responses and tissue homeostasis [4,5,7]. Aberrant activation of this pathway contributes to chronic inflammatory diseases, including Crohn's disease-like intestinal inflammation and hidradenitis suppurativa, and has been implicated in colitis-associated colon cancer [1,5,8]. Understanding the enzymatic mechanism, regulation, and genetic dependencies of muramyl dipeptide kinase activity is therefore essential for developing targeted therapies that modulate NOD2 signaling. This article synthesizes current knowledge from authoritative GO annotations and peer-reviewed literature to provide a research-grade overview for scientists and AI-driven discovery platforms.
muramyl dipeptide kinase activity At A Glance
| GO ID | GO:0160047 |
|---|---|
| GO term | muramyl dipeptide kinase activity |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Phosphorylation of muramyl dipeptide to 6-O-phospho-muramyl dipeptide using ATP |
| Reaction | ATP + muramyl dipeptide = ADP + H+ + 6-O-phospho-muramyl dipeptide |
| Enzyme | N-acetylglucosamine kinase (NAGK) in humans |
| Substrate | Muramyl dipeptide (MDP) |
| Product | 6-O-phospho-muramyl dipeptide |
| Biological context | Innate immune sensing of bacterial peptidoglycan; NOD2 activation [4,5] |
What Is GO:0160047?
According to the Gene Ontology, muramyl dipeptide kinase activity (GO:0160047) is defined as the catalysis of the reaction: ATP + muramyl dipeptide = ADP + H+ + 6-O-phospho-muramyl dipeptide. In other words, it is the enzyme activity that phosphorylates muramyl dipeptide at the 6-hydroxy position of the muramic acid moiety, using ATP as the phosphate donor. This activity is a molecular function that enables the production of phospho-MDP, a key metabolite for NOD2-dependent immune signaling [4,5].
Why Is muramyl dipeptide kinase activity Important in Cell Biology?
Muramyl dipeptide kinase activity is important because it generates the specific ligand that activates NOD2, a central innate immune sensor of bacterial peptidoglycan [4,5]. This activity thus directly controls the intensity and duration of inflammatory signaling in response to microbial exposure. Dysregulation of the NOD2 pathway, in which this kinase activity is a critical step, is associated with inflammatory bowel diseases, colorectal cancer progression, and autoinflammatory skin conditions [1,3,5,8]. Targeting this enzymatic step could offer new therapeutic strategies for modulating innate immunity and treating inflammation-driven diseases.
• Provides the essential phosphorylation step that converts MDP into a NOD2 agonist.
• Links bacterial cell wall metabolism to host innate immune activation [4,5].
• Modulates inflammatory responses in intestinal epithelium and immune cells.
• Implicated in colitis-associated colon cancer development.
• Contributes to colorectal cancer metastasis through RIPK2-YAP signaling.
• Associated with hidradenitis suppurativa, a chronic inflammatory skin disease.
• Potential target for anti-inflammatory therapeutics [5,7].
• Key node for understanding host-microbiome interactions.
• Enables experimental dissection of NOD2 ligand specificity.
• Relevant to vaccine adjuvant development based on MDP derivatives.
Molecular Mechanism of muramyl dipeptide kinase activity
Substrate recognition and binding
In simple terms: The enzyme grabs MDP and ATP to start the reaction.
NAGK, the enzyme responsible for muramyl dipeptide kinase activity, binds muramyl dipeptide (MDP) and ATP in its active site. Structural and biochemical studies indicate that NAGK recognizes the sugar moiety of MDP, similar to its canonical substrate N-acetylglucosamine, but with distinct specificity that allows phosphorylation of MDP. This binding is the first step in generating the NOD2 ligand.
Catalytic transfer of phosphate
In simple terms: The enzyme moves a phosphate from ATP onto MDP.
Following substrate binding, NAGK catalyzes the transfer of the gamma-phosphate from ATP to the 6-hydroxyl group of the muramic acid residue in MDP, producing 6-O-phospho-MDP, ADP, and a proton. This phosphorylation is essential for MDP to acquire NOD2-stimulating activity, as unmodified MDP is a poor agonist.
Product release and NOD2 activation
In simple terms: The modified MDP is released and triggers immune signaling.
After catalysis, 6-O-phospho-MDP is released from NAGK and can bind to the NOD2 receptor in the cytoplasm [4,5]. This binding induces NOD2 oligomerization and recruitment of RIPK2, initiating downstream signaling that leads to NF-kB activation and pro-inflammatory cytokine production [4,5,7].
Regulation by cellular context
In simple terms: The activity can be tuned by other proteins and cellular states.
The efficiency of MDP phosphorylation and subsequent NOD2 activation can be modulated by the availability of NAGK, ATP levels, and the presence of regulatory proteins such as DUBA, which stabilizes NOD2 and RIPK2 to sustain signaling. Additionally, crosstalk with other innate immune pathways, such as TLR2, can influence the overall response.
Integration with innate immune signaling
In simple terms: This activity is part of a larger immune detection system.
Muramyl dipeptide kinase activity is a critical node in the NOD2 signaling axis, which integrates signals from bacterial peptidoglycan to mount appropriate immune responses. This pathway intersects with autophagy, NF-kB, and MAPK signaling, and its dysregulation can lead to chronic inflammation and cancer [1,3,5].
Key Genes Involved in GO:0160047 muramyl dipeptide kinase activity
The following genes and proteins are directly involved in or regulate muramyl dipeptide kinase activity and its downstream signaling.
| Gene | Major Role | Research Relevance |
|---|---|---|
| NAGK | Enzyme catalyzing phosphorylation of MDP to 6-O-phospho-MDP | Directly responsible for GO:0160047 activity; knockout reduces NOD2 activation |
| NOD2 | Cytoplasmic receptor for 6-O-phospho-MDP; initiates innate immune signaling | Mutations linked to Crohn's disease and Blau syndrome; central to pathway |
| RIPK2 | Serine/threonine kinase recruited by NOD2; mediates NF-kB and MAPK activation | Required for NOD2 signaling; promotes colorectal cancer metastasis [3,7] |
| YAP | Transcriptional co-activator; regulated by RIPK2-ITCH axis | RIPK2 protects YAP from degradation, promoting metastasis |
| ITCH | E3 ubiquitin ligase that targets YAP for degradation | Modulates YAP stability downstream of NOD2-RIPK2 |
| DUBA | Deubiquitinase that stabilizes NOD2 and RIPK2 | Enhances innate immune responses; potential therapeutic target |
| TLR2 | Toll-like receptor sensing bacterial lipoteichoic acid; crosstalks with NOD2 | Potentiates MDP-induced nitric oxide production |
| PAFR | Platelet-activating factor receptor; involved in MDP/LTA signaling | Mediates synergistic inflammatory responses |
| ATG16L1 | Autophagy-related protein; interacts with NOD2 pathway | Autophagy modulates colitis-associated cancer; risk factor for IBD |
| NFKB1 | Transcription factor downstream of NOD2-RIPK2 | Drives pro-inflammatory gene expression |
| MAPK1 | Kinase in MAPK cascade activated by NOD2 | Contributes to cytokine production |
| IL6 | Pro-inflammatory cytokine induced by NOD2 signaling | Marker of inflammation in IBD and cancer models |
| TNF | Pro-inflammatory cytokine induced by NOD2 signaling | Key mediator of inflammation |
| CXCL8 | Chemokine induced by NOD2 activation | Recruits neutrophils to sites of infection |
| NLRP3 | Inflammasome sensor; crosstalks with NOD2 | Modulates IL-1beta production |
| CASP1 | Inflammasome caspase; activated downstream of NLRP3 | Mediates cytokine maturation |
How Is muramyl dipeptide kinase activity Regulated?
Muramyl dipeptide kinase activity is primarily regulated by the expression and activity of NAGK, the enzyme responsible for this phosphorylation. Cellular ATP levels and the availability of MDP substrate also influence the reaction rate. Downstream signaling is further controlled by ubiquitination and deubiquitination events: DUBA stabilizes NOD2 and RIPK2, enhancing pathway output, while ITCH-mediated ubiquitination of YAP limits its pro-metastatic function. Additionally, crosstalk with TLR2 signaling can potentiate the response to MDP. Autophagy pathways, involving ATG16L1, can modulate NOD2 signaling and inflammation.
muramyl dipeptide kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| NOD2 | Crohn's disease, Blau syndrome | NOD2 knockout mice, patient-derived organoids |
| RIPK2 | Colorectal cancer metastasis | RIPK2 knockout or knockdown in CRC cell lines, xenograft models |
| NAGK | Innate immune deficiency (implied) | NAGK knockout cell lines, kinase-dead mutants |
| ATG16L1 | Inflammatory bowel disease, colitis-associated cancer | ATG16L1 knockout mice, DSS-induced colitis |
| DUBA | Autoinflammatory disorders | DUBA knockout or overexpression in macrophages |
Inflammatory bowel disease and colitis-associated cancer
Dysregulated NOD2 signaling, downstream of muramyl dipeptide kinase activity, is strongly associated with Crohn's disease and ulcerative colitis. Chronic inflammation increases the risk of colitis-associated colon cancer, where autophagy and NOD2 pathways play complex roles. Targeting the kinase activity or its products may reduce inflammation-driven tumorigenesis.
Colorectal cancer metastasis
RIPK2, activated downstream of NOD2, promotes colorectal cancer metastasis by protecting YAP from ITCH-mediated ubiquitination. This suggests that muramyl dipeptide kinase activity, by driving NOD2-RIPK2 signaling, could contribute to metastatic progression and represents a potential therapeutic target.
Hidradenitis suppurativa
NOD2 signaling is implicated in hidradenitis suppurativa, a chronic inflammatory skin disease. Aberrant activation of the pathway, potentially due to increased muramyl dipeptide kinase activity, may exacerbate skin inflammation.
Bone and joint inflammation
Muramyl dipeptide, the substrate of this kinase, plays a role in osteoclast activity and inflammatory bone loss. Phosphorylation may modulate these effects, linking the activity to bone pathologies.
From muramyl dipeptide kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does NAGK knockout abolish MDP-induced NOD2 activation? | NAGK knockout HEK293T or macrophage cell lines |
| What is the effect of a kinase-dead NAGK mutation on immune signaling? | Point mutation (e.g., D107A) knock-in via CRISPR |
| Can tagged NAGK reveal its subcellular localization? | Knock-in of FLAG- or GFP-NAGK in immune cells |
| Does NAGK overexpression enhance NOD2-dependent inflammation? | NAGK overexpression in intestinal epithelial cells or macrophages |
| Which genes modulate the MDP kinase pathway? | CRISPR library screening in NOD2 reporter cells [4,7] |
| Does RIPK2 knockout reduce metastasis in CRC? | RIPK2 knockout in CRC cell lines and mouse xenografts |
How to Study the muramyl dipeptide kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro kinase assay | Phosphorylation of MDP to 6-O-phospho-MDP | Enzyme kinetics, inhibitor testing |
| CRISPR knockout screen | Genes required for MDP-induced NOD2 activation | Discovery of pathway components [4,7] |
| Phosphoproteomics | Changes in protein phosphorylation upon MDP stimulation | Mapping signaling networks |
| Metabolomics | Quantification of 6-O-phospho-MDP | Direct measurement of enzyme activity in cells |
| NF-kB reporter assay | Activation of NF-kB downstream of NOD2 | Functional validation of kinase activity [4,5] |
| Co-immunoprecipitation | Protein-protein interactions (e.g., NAGK-MDP, NOD2-RIPK2) | Mechanistic studies [4,7] |
| RNA-seq | Transcriptional changes upon pathway activation | Identifying downstream inflammatory genes [1,5] |
| Immunofluorescence | Subcellular localization of NAGK, NOD2, RIPK2 | Visualizing pathway assembly [4,7] |
Kinase activity assays
In vitro kinase assays using recombinant NAGK and synthetic MDP, followed by detection of 6-O-phospho-MDP by mass spectrometry or HPLC, directly measure muramyl dipeptide kinase activity. These assays are essential for validating enzyme kinetics and inhibitor efficacy.
CRISPR-based genetic screens
Genome-wide CRISPR knockout or activation screens in NOD2 reporter cell lines can identify genes that regulate MDP-induced signaling, including NAGK and its modifiers [4,7]. Such screens are powerful for discovering novel pathway components.
Phosphoproteomics and metabolomics
Mass spectrometry-based phosphoproteomics can detect changes in NOD2 and RIPK2 phosphorylation upon MDP stimulation, while metabolomics can quantify 6-O-phospho-MDP levels. These approaches provide systems-level insights.
Immune signaling reporter assays
NF-kB or cytokine reporter assays in macrophages or epithelial cells treated with MDP or phospho-MDP measure downstream pathway activation [4,5]. Combining with CRISPR knockouts allows functional dissection of the kinase activity.
How CRISPR Can Be Used to Study GO:0160047 muramyl dipeptide kinase activity
Knockout
CRISPR knockout of NAGK eliminates muramyl dipeptide kinase activity, preventing 6-O-phospho-MDP production and NOD2 activation. This model is useful to test the requirement of the kinase for immune responses and to identify compensatory pathways. Knockout of NOD2 or RIPK2 similarly blocks downstream signaling [3,5].
Point Mutation
Introducing point mutations in the NAGK catalytic domain (e.g., aspartate to alanine) via CRISPR knock-in creates kinase-dead variants that can distinguish enzymatic activity from scaffolding functions. Such models help dissect the specific contribution of MDP phosphorylation to NOD2 activation.
Knock-in
Knock-in of epitope-tagged NAGK (e.g., FLAG, HA) allows endogenous-level expression and localization studies without overexpression artifacts. Tagged NOD2 or RIPK2 knock-ins can similarly facilitate interaction and trafficking studies.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of NAGK increases MDP phosphorylation and enhances NOD2 signaling, useful for gain-of-function studies in inflammation and cancer models [4,7]. Overexpression of DUBA, for example, stabilizes NOD2 and RIPK2, amplifying responses.
How EDITGENE Supports muramyl dipeptide kinase activity Research
Researchers studying muramyl dipeptide kinase activity-related genes often need to determine whether a candidate gene is causally involved in the pathway or merely correlated with its activation. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such causal investigations, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for muramyl dipeptide kinase activity research.
Frequently Asked Questions About muramyl dipeptide kinase activity
What is muramyl dipeptide kinase activity?
It is the enzyme activity that phosphorylates muramyl dipeptide (MDP) to 6-O-phospho-MDP using ATP, as defined by GO:0160047.
What gene encodes muramyl dipeptide kinase activity?
In humans, the enzyme responsible is N-acetylglucosamine kinase (NAGK).
What is the reaction catalyzed by muramyl dipeptide kinase?
ATP + muramyl dipeptide = ADP + H+ + 6-O-phospho-muramyl dipeptide.
Why is muramyl dipeptide phosphorylation important?
Phosphorylated MDP is the specific ligand that activates NOD2, a key innate immune receptor, triggering inflammatory responses [4,5].
What diseases are associated with muramyl dipeptide kinase activity?
Dysregulation of the pathway is linked to inflammatory bowel diseases, colorectal cancer, and hidradenitis suppurativa [1,3,5,8].
How can I study muramyl dipeptide kinase activity in the lab?
Use in vitro kinase assays, CRISPR knockout of NAGK, and NOD2 reporter assays to measure downstream activation.
What are the substrates of muramyl dipeptide kinase?
The substrates are ATP and muramyl dipeptide.
What is the product of muramyl dipeptide kinase activity?
The product is 6-O-phospho-muramyl dipeptide, along with ADP and a proton.
Is muramyl dipeptide kinase activity involved in cancer?
Yes, downstream signaling through RIPK2 and YAP promotes colorectal cancer metastasis.
What CRISPR models are available for studying this pathway?
Knockout, point mutation, knock-in, and overexpression models for NAGK, NOD2, RIPK2, and related genes [4,7].
Conclusion
Muramyl dipeptide kinase activity (GO:0160047) is a critical enzymatic step that converts bacterial MDP into a potent NOD2 agonist, thereby shaping innate immune responses and influencing inflammatory diseases and cancer [4,5]. Understanding its mechanism, regulation, and genetic dependencies offers opportunities for therapeutic intervention. EDITGENE provides comprehensive CRISPR solutions to accelerate research in this pathway.
References
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- 3. Lu C et al.. 2025. RIPK2 promotes colorectal cancer metastasis by protecting YAP degradation from ITCH-mediated ubiquitination.. Cell Death Dis 16(1):248 PMID: 40185717
- 4. Stafford CA et al.. 2022. Phosphorylation of muramyl peptides by NAGK is required for NOD2 activation.. Nature 609(7927):590-596 PMID: 36002575
- 5. Al Nabhani Z et al.. 2017. Nod2: The intestinal gate keeper.. PLoS Pathog 13(3):e1006177 PMID: 28253332
- 6. Im J et al.. 2024. Muramyl dipeptide potentiates Staphylococcus aureus lipoteichoic acid-induced nitric oxide production via TLR2/NOD2/PAFR signaling pathways.. Front Immunol 15:1451315 PMID: 39712020
- 7. Zhou B et al.. 2025. DUBA sustains the stability of NOD2 and RIPK2 to enhance innate immune responses.. Cell Death Differ 32(11):2053-2065 PMID: 40240520
- 8. Gambichler T et al.. 2021. NOD2 signalling in hidradenitis suppurativa.. Clin Exp Dermatol 46(8):1488-1494 PMID: 34056759
