GO:0003810 protein-glutamine gamma-glutamyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0003810 describes the enzymatic activity that forms N6-(L-isoglutamyl)-L-lysine isopeptide bonds between peptidyl-glutamine and peptidyl-lysine residues, cross-linking polypeptide chains.
• This activity is catalysed by transglutaminases, including factor XIIIa (fibrinoligase) and tissue transglutaminase (TG2), and produces ammonia as a by-product.
• Factor XIIIa stabilises fibrin clots by cross-linking fibrin gamma and alpha chains, a critical step in haemostasis and wound repair.
• TG2 is a multifunctional enzyme involved in celiac disease, cancer, neuroinflammation, and senescence through deamidation and transamidation reactions.
• Dysregulated transglutaminase activity contributes to autoimmune, fibrotic, neurodegenerative, and neoplastic pathologies, making it a therapeutic target.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable precise dissection of transglutaminase gene function in disease.
Description
Protein-glutamine gamma-glutamyltransferase activity (GO:0003810) is a molecular function that catalyses the formation of an isopeptide bond between the gamma-carboxamide group of a peptidyl-glutamine residue and the epsilon-amino group of a peptidyl-lysine residue, releasing ammonia and creating intra- or intermolecular N6-(5-glutamyl)lysine cross-links. This reaction is central to protein cross-linking in diverse biological contexts, from blood coagulation to extracellular matrix stabilisation and cell death. The enzymes responsible, transglutaminases, are calcium-dependent thiol transferases that include factor XIIIa (fibrinoligase) and tissue transglutaminase (TG2). Researchers study GO:0003810 because its dysregulation is implicated in thrombosis, celiac disease, cancer, and neurodegeneration. Understanding the catalytic mechanism and regulation of transglutaminases provides opportunities for therapeutic intervention and for engineering cell models that mimic human disease. This article synthesises authoritative QuickGO data and verified PubMed literature to outline the mechanism, key genes, disease relevance, and CRISPR-based research strategies for GO:0003810.
protein-glutamine gamma-glutamyltransferase activity At A Glance
| GO ID | GO:0003810 |
|---|---|
| GO term | protein-glutamine gamma-glutamyltransferase activity |
| Ontology | molecular_function |
| Synonym | transglutaminase activity; factor XIIIa; fibrinoligase activity; fibrin stabilizing factor; TGase activity; tissue transglutaminase |
| Major function | Catalyses isopeptide bond formation between glutamine and lysine residues, cross-linking proteins |
| Reaction | L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4+ |
| Cofactors | Calcium ions; thiol group at active site |
| Subcellular location | Cytoplasm, extracellular matrix, plasma membrane |
| Representative enzymes | Factor XIIIa (F13A1), tissue transglutaminase (TGM2), other transglutaminases |
What Is GO:0003810?
GO:0003810, protein-glutamine gamma-glutamyltransferase activity, is defined as the catalysis of the reaction: L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4+. In this reaction, the gamma-carboxamide groups of peptidyl-glutamine residues act as acyl donors, and the 6-amino groups of peptidyl-lysine residues act as acceptors, forming intra- and intermolecular N6-(5-glutamyl)lysine cross-links. This activity is synonymous with transglutaminase activity, factor XIIIa, fibrinoligase, fibrin stabilising factor, and tissue transglutaminase, among other names.
Why Is protein-glutamine gamma-glutamyltransferase activity Important in Cell Biology?
GO:0003810 is essential for post-translational protein cross-linking that stabilises fibrin clots, extracellular matrix, and cell structures, and it also mediates deamidation and monoaminylation reactions that regulate signalling and gene expression. Dysregulated transglutaminase activity is linked to thrombotic disorders, celiac disease, cancer progression, and neuroinflammation, making it a high-value target for both basic research and drug discovery.
• Stabilises fibrin clots through factor XIIIa-mediated cross-linking, preventing premature fibrinolysis.
• Drives extracellular matrix assembly and tissue repair by cross-linking matrix proteins.
• Mediates celiac disease pathogenesis via TG2-catalysed deamidation of gluten peptides, enhancing their immunogenicity.
• Contributes to cancer progression through TG2-mediated histone monoaminylation and modulation of gene expression.
• Regulates senescence by deamidating p21 and enhancing its stability.
• Promotes neuroinflammation and neurodegeneration through TG2 activity in the central nervous system.
• Serves as a therapeutic target for anticoagulation, celiac disease, fibrosis, and cancer.
• Provides a paradigm for studying calcium-dependent thiol transferases and post-translational modifications.
• Enables CRISPR-based disease modelling to dissect isoform-specific functions.
• Facilitates development of inhibitors and activity-based probes for transglutaminases.
What Happens During protein-glutamine gamma-glutamyltransferase activity?
Substrate recognition and acyl-enzyme intermediate formation
In simple terms: The enzyme grabs a glutamine residue on one protein and forms a temporary bond with it.
Transglutaminases recognise peptidyl-glutamine residues in substrate proteins and form a thioester acyl-enzyme intermediate through a catalytic cysteine residue, releasing ammonia. This step is calcium-dependent and requires the gamma-carboxamide group of glutamine as the acyl donor.
Isopeptide bond formation with lysine acceptor
In simple terms: The enzyme then links the glutamine to a lysine on another protein, creating a strong cross-link.
The acyl-enzyme intermediate reacts with the epsilon-amino group of a peptidyl-lysine residue on a second protein, forming an N6-(5-glutamyl)lysine isopeptide bond and releasing the enzyme. This cross-linking can occur between different polypeptide chains (intermolecular) or within the same chain (intramolecular).
Deamidation as a competing reaction
In simple terms: Sometimes the enzyme just removes an ammonia group from glutamine, changing the protein's charge.
In the absence of a suitable lysine acceptor, transglutaminases can catalyse deamidation of glutamine residues, converting them to glutamate and releasing ammonia. This reaction is particularly relevant for TG2-mediated deamidation of gluten peptides in celiac disease and of p21 during senescence.
Monoaminylation and polyamination
In simple terms: The enzyme can also attach small amines like serotonin to proteins, modifying their function.
Transglutaminases can transfer primary amines, including monoamines such as serotonin and dopamine, to glutamine residues, a reaction termed monoaminylation. This activity links transglutaminases to epigenetic regulation and cancer biology.
Key Genes Involved in GO:0003810 protein-glutamine gamma-glutamyltransferase activity
The following genes encode transglutaminase enzymes or related proteins that carry out or regulate GO:0003810 activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TGM2 | Tissue transglutaminase; catalyses deamidation, transamidation, and monoaminylation | Implicated in celiac disease, cancer, neuroinflammation, and senescence |
| F13A1 | Factor XIII A subunit; forms the catalytic domain of factor XIIIa | Essential for fibrin cross-linking and clot stability |
| F13B | Factor XIII B subunit; carrier protein for F13A1 | Regulates factor XIII activity and stability |
| TGM1 | Keratinocyte transglutaminase; cross-links cornified envelope proteins | Skin barrier formation and ichthyosis |
| TGM3 | Epidermal transglutaminase; involved in hair and skin differentiation | Hair shaft formation and skin disorders |
| TGM4 | Prostate transglutaminase; role in semen coagulation | Prostate biology and cancer |
| TGM5 | Epidermal transglutaminase; cross-links epidermal proteins | Peeling skin syndrome |
| TGM6 | Neuronal transglutaminase; role in neurodegeneration | Spinocerebellar ataxia and neuroprotection |
| TGM7 | Transglutaminase 7; expressed in testis and prostate | Reproductive biology |
| EPB42 | Erythrocyte membrane protein band 4.2; transglutaminase-like protein | Red blood cell membrane stability |
| ITGA2 | Integrin alpha-2; interacts with TG2 in cell adhesion | Cell migration and matrix remodelling |
| FN1 | Fibronectin; substrate for TG2-mediated cross-linking | Extracellular matrix assembly |
| COL1A1 | Collagen type I alpha 1; cross-linked by transglutaminases | Fibrosis and connective tissue disorders |
| HLA-DQ2 | MHC class II molecule; presents deamidated gluten peptides | Celiac disease susceptibility |
| CD4 | T cell co-receptor; mediates helper T cell response to gluten | Celiac disease immunopathogenesis |
| IL15 | Cytokine; amplifies intraepithelial lymphocyte activation | Celiac disease and autoimmunity |
| CDH1 | E-cadherin; regulated by TG2 in epithelial cells | Cancer invasion and metastasis |
How Is protein-glutamine gamma-glutamyltransferase activity Regulated?
Transglutaminase activity is regulated at multiple levels. Calcium binding is required for catalytic activity, and intracellular calcium levels control enzyme activation. GTP binding to TG2 inhibits its transamidation activity and promotes a closed conformation. Redox state modulates the catalytic cysteine, with oxidative stress affecting activity. Transcriptional regulation of TGM2 occurs in response to inflammatory cytokines and growth factors. In cancer, TG2 expression is upregulated by NF-kB and hypoxia-inducible factors. Factor XIIIa activity is regulated by thrombin cleavage and calcium binding.
protein-glutamine gamma-glutamyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TGM2 | Celiac disease, cancer, neuroinflammation | TGM2 knockout intestinal organoids; point-mutation of catalytic cysteine |
| F13A1 | Factor XIII deficiency, thrombosis | F13A1 knockout mice; knock-in of patient mutations |
| TGM1 | Ichthyosis, skin barrier defects | TGM1 knockout keratinocytes; overexpression of wild-type and mutant |
| TGM6 | Spinocerebellar ataxia | TGM6 knockout neurons; point-mutation models |
| TGM5 | Peeling skin syndrome | TGM5 knockout skin equivalents |
Celiac disease
In celiac disease, TG2 deamidates gluten peptides, increasing their affinity for HLA-DQ2 or HLA-DQ8 molecules and triggering a CD4+ T cell-mediated immune response that damages the small intestine. TG2-specific autoantibodies are a hallmark of the disease. A dendritic cell population responsible for TG2-mediated gluten antigen presentation has been identified, highlighting the role of TG2 in immune activation.
Cancer
TG2 is overexpressed in many cancers and contributes to tumour progression, metastasis, and drug resistance. TG2-mediated histone monoaminylation regulates gene expression and promotes cancer stemness. TG2 also stabilises p21 during senescence, linking transglutaminase activity to cell cycle control and tumour suppression.
Neuroinflammation and neurodegeneration
TG2 is upregulated in neuroinflammatory conditions and contributes to neuronal damage through cross-linking of proteins and activation of inflammatory pathways. TG2-mediated deamidation and monoaminylation may affect neuronal signalling and survival.
Thrombosis and bleeding disorders
Factor XIIIa deficiency leads to defective fibrin cross-linking and bleeding diathesis, while excessive factor XIIIa activity may contribute to thrombosis. Factor XIIIa stabilises clots by cross-linking fibrin and antiplasmin, and its dysfunction is associated with impaired wound healing.
From protein-glutamine gamma-glutamyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does TGM2 catalytic activity drive celiac disease pathogenesis? | TGM2 knockout or point-mutation (C277S) in intestinal epithelial cells |
| How does factor XIIIa cross-linking affect clot stability? | F13A1 knockout mice or knock-in of patient mutations |
| What is the role of TG2 in cancer stemness? | TGM2 overexpression and knockout in cancer cell lines |
| Does TG2-mediated histone monoaminylation regulate gene expression? | TGM2 knockout with histone monoaminylation profiling |
| How does TG2 deamidation affect p21 stability? | TGM2 knockout and point-mutation in senescence models |
| Can transglutaminase inhibitors be tested in disease models? | Knock-in of fluorescent-tagged TGM2 for activity imaging |
How to Study the protein-glutamine gamma-glutamyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Mass spectrometry | Isopeptide cross-links and deamidation sites | Identification of transglutaminase substrates in cell lysates |
| Fluorescent amine incorporation assay | Transglutaminase enzymatic activity | Inhibitor screening and kinetic studies |
| CRISPR knockout screens | Genes required for transglutaminase activity or toxicity | Cancer and celiac disease target discovery |
| Western blot | Protein expression and cross-linking | Validation of knockout or overexpression models |
| Immunohistochemistry | Tissue distribution of transglutaminases | Disease pathology studies |
| Live-cell imaging | Real-time transglutaminase activity | Wound healing and matrix assembly |
| RNA-seq | Transcriptional changes upon transglutaminase modulation | Pathway analysis in disease models |
| Proximity ligation assay | Protein-protein interactions involving transglutaminases | Substrate recognition studies |
Proteomic identification of cross-linked proteins
Mass spectrometry-based proteomics can identify N6-(5-glutamyl)lysine cross-links and deamidated peptides in cell lysates, revealing transglutaminase substrates and interaction networks. This approach has been used to map TG2-mediated modifications in disease models.
Activity assays and inhibitor screening
Transglutaminase activity can be measured using fluorescent substrates such as cadaverine or biotinylated amines, enabling high-throughput screening of inhibitors. Calcium dependence and GTP inhibition can be assessed in vitro.
CRISPR-based genetic screens
Genome-wide CRISPR knockout screens can identify genes that modulate transglutaminase activity or sensitivity to transglutaminase inhibitors. Such screens have revealed synthetic lethal interactions in cancer cells.
Imaging of transglutaminase activity
Fluorescent probes and activity-based probes allow visualisation of transglutaminase activity in live cells and tissues, providing spatial and temporal information. This is useful for studying extracellular matrix cross-linking and wound healing.
How CRISPR Can Be Used to Study GO:0003810 protein-glutamine gamma-glutamyltransferase activity
Knockout
CRISPR knockout of TGM2 or F13A1 eliminates transglutaminase activity, enabling studies of its role in celiac disease, cancer, and thrombosis. Knockout cell lines are valuable for identifying compensatory pathways and for validating inhibitor specificity.
Point Mutation
Point mutations in the catalytic cysteine (e.g., C277S in TGM2) abolish transglutaminase activity while preserving protein structure, allowing separation of catalytic and non-catalytic functions. Such models are critical for dissecting deamidation versus transamidation.
Knock-in
Knock-in of disease-associated mutations (e.g., F13A1 variants) or fluorescent tags (e.g., GFP-TGM2) enables real-time tracking of enzyme localisation and activity in physiological contexts. Knock-in models also facilitate study of isoform-specific functions.
Overexpression
Overexpression of wild-type or mutant TGM2 in cell lines mimics pathological upregulation observed in cancer and neuroinflammation, allowing investigation of downstream signalling and therapeutic targeting. Overexpression models are also used to study substrate specificity.
How EDITGENE Supports protein-glutamine gamma-glutamyltransferase activity Research
Researchers studying protein-glutamine gamma-glutamyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in disease or whether its catalytic activity is required for a specific phenotype. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for protein-glutamine gamma-glutamyltransferase activity research.
Frequently Asked Questions About protein-glutamine gamma-glutamyltransferase activity
What is protein-glutamine gamma-glutamyltransferase activity?
It is the enzymatic activity (GO:0003810) that forms isopeptide bonds between glutamine and lysine residues in proteins, cross-linking them and releasing ammonia.
What genes are involved in protein-glutamine gamma-glutamyltransferase activity?
The main genes are TGM2 (tissue transglutaminase) and F13A1 (factor XIII A subunit), along with other transglutaminase family members such as TGM1, TGM3, TGM5, and TGM6.
How is protein-glutamine gamma-glutamyltransferase activity regulated?
It is regulated by calcium binding, GTP inhibition, redox state, and transcriptional control by inflammatory cytokines.
What diseases are associated with transglutaminase activity?
Celiac disease, cancer, neuroinflammation, thrombosis, and skin disorders are linked to dysregulated transglutaminase activity.
How can I study transglutaminase activity in the lab?
Common methods include fluorescent amine incorporation assays, mass spectrometry for cross-link identification, and CRISPR knockout models.
What is the role of TG2 in celiac disease?
TG2 deamidates gluten peptides, increasing their immunogenicity and triggering a T cell-mediated immune response in the small intestine.
Can CRISPR be used to knockout TGM2?
Yes, CRISPR-Cas9 knockout of TGM2 is widely used to study loss of transglutaminase activity in cancer and celiac disease models.
What is factor XIIIa and how does it relate to GO:0003810?
Factor XIIIa is the activated form of coagulation factor XIII that cross-links fibrin through transglutaminase activity, stabilising blood clots.
What are the substrates of transglutaminases?
Substrates include fibrin, fibronectin, collagen, gluten peptides, and histones, among others.
How does transglutaminase activity contribute to cancer?
TG2-mediated histone monoaminylation and deamidation of p21 regulate gene expression and cell survival, promoting cancer progression.
Conclusion
GO:0003810, protein-glutamine gamma-glutamyltransferase activity, is a fundamental enzymatic function that cross-links proteins and modifies their properties through isopeptide bond formation, deamidation, and monoaminylation. Its dysregulation is implicated in a wide range of human diseases, from celiac disease to cancer and neurodegeneration. CRISPR-based models, including knockout, point mutation, knock-in, and overexpression, provide powerful tools to dissect the precise roles of transglutaminases in health and disease. Continued research into this activity will likely yield new therapeutic strategies targeting transglutaminase enzymes.
References
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- 4. Liao YW et al.. 2025. Transglutaminase 2-mediated glutamine deamidation enhances p21 stability during senescence.. Proc Natl Acad Sci U S A 122(24):e2419762122 PMID: 40498452
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