GO:0004478 methionine adenosyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004478 methionine adenosyltransferase activity catalyzes the reaction ATP + L-methionine + H2O = phosphate + diphosphate + S-adenosyl-L-methionine.
• The enzymes MAT1A, MAT2A, and MAT2B are the principal human proteins carrying this activity, with MAT2A being the widely expressed catalytic subunit.
• S-adenosylmethionine (SAM) produced by this activity is the major methyl donor for methylation reactions and a key regulator of polyamine synthesis and transsulfuration.
• MTAP-deleted cancers are selectively vulnerable to MAT2A inhibition, which reduces PRMT5-dependent mRNA splicing and induces DNA damage.
• MAT2A is a therapeutic target in liver cancer, atherosclerosis, and MTAP-deleted osteosarcoma, where methionine intervention can enhance immune checkpoint therapy.
• CRISPR knockout, point mutation, knock-in, and overexpression models are essential to dissect the causal roles of MAT1A, MAT2A, and MAT2B in disease.
Description
Methionine adenosyltransferase activity (GO:0004478) is a molecular function that catalyzes the formation of S-adenosyl-L-methionine (SAM) from ATP and L-methionine. This reaction is the sole route for SAM biosynthesis in mammals, making it a central node in one-carbon metabolism, methylation, and polyamine synthesis. The enzyme is encoded by MAT1A (liver-specific) and MAT2A (ubiquitous), with MAT2B acting as a regulatory subunit. Because SAM is the principal methyl donor for DNA, RNA, protein, and lipid methylation, the activity of methionine adenosyltransferase influences gene expression, cell proliferation, and redox balance. Dysregulation of methionine adenosyltransferase activity is implicated in liver disease, cancer, and metabolic disorders. In cancer, MTAP deletions create a dependency on MAT2A, and MAT2A inhibition selectively kills MTAP-deleted tumor cells by disrupting PRMT5-dependent splicing and inducing DNA damage. In atherosclerosis, MAT2A promotes plaque vulnerability through epigenetic reprogramming of macrophages. These findings have made methionine adenosyltransferase a high-priority target for therapeutic intervention and a model system for studying metabolic enzymes. For researchers, GO:0004478 represents both a biochemical reaction and a regulatory hub. Understanding its mechanism, regulation, and disease relevance requires integrating structural biology, enzymology, and functional genomics. This article provides a research-grade overview of the term, its genes, disease connections, and the CRISPR-based methods used to study it.
methionine adenosyltransferase activity At A Glance
| GO ID | GO:0004478 |
|---|---|
| GO term | methionine adenosyltransferase activity |
| Ontology | molecular_function |
| Synonym | adenosylmethionine synthetase activity; AdoMet synthetase activity; ATP:L-methionine S-adenosyltransferase activity; methionine-activating enzyme; S-adenosylmethionine synthase activity |
| Major function | Catalyzes the synthesis of S-adenosyl-L-methionine (SAM) from ATP and L-methionine |
| Reaction | ATP + L-methionine + H2O = phosphate + diphosphate + S-adenosyl-L-methionine |
| Cofactors | Requires Mg2+ and K+ for optimal activity |
| Subcellular location | Cytosol; MAT1A is liver-specific, MAT2A is ubiquitous |
| Human genes | MAT1A, MAT2A, MAT2B |
What Is GO:0004478?
Methionine adenosyltransferase activity (GO:0004478) is defined as the catalysis of the reaction: ATP + L-methionine + H2O = phosphate + diphosphate + S-adenosyl-L-methionine. In other words, it is the enzyme activity that activates methionine by transferring the adenosyl group of ATP to methionine, producing SAM, the universal methyl donor. This activity is essential for all transmethylation reactions and for the synthesis of polyamines and glutathione.
Why Is methionine adenosyltransferase activity Important in Cell Biology?
Methionine adenosyltransferase activity is indispensable for life because it produces SAM, the primary methyl donor for all biological methylation reactions and a precursor for polyamines and glutathione. Its dysregulation leads to liver injury, cancer, and metabolic disease, and it has emerged as a synthetic lethal target in MTAP-deleted cancers. Understanding this activity is therefore critical for both basic metabolism research and therapeutic development.
• Produces SAM, the universal methyl donor required for DNA, RNA, protein, and lipid methylation.
• Regulates polyamine synthesis and transsulfuration, influencing cell growth and redox homeostasis.
• MAT2A is synthetically lethal with MTAP deletion in multiple cancers, including glioblastoma and osteosarcoma.
• MAT1A downregulation is associated with poor prognosis in hepatocellular carcinoma.
• MAT2A promotes atherosclerotic plaque vulnerability via epigenetic reprogramming of macrophages.
• Methionine adenosyltransferase activity is a biomarker for methionine dependency in cancer.
• Enzyme engineering studies reveal key electrostatic interactions that enhance catalytic activity, informing inhibitor design.
• CRISPR models of MAT1A/MAT2A/MAT2B enable causal dissection of SAM metabolism in disease.
What Happens During methionine adenosyltransferase activity?
Substrate binding and activation
In simple terms: The enzyme grabs ATP and methionine and prepares them to react.
Methionine adenosyltransferase binds ATP and L-methionine in a sequential ordered mechanism, with ATP binding first. The enzyme requires divalent cations such as Mg2+ and monovalent K+ for optimal activity, which stabilize the ATP phosphate groups and facilitate nucleophilic attack. Structural studies of MAT2A have revealed that electrostatic interactions in the active site are critical for substrate positioning and catalysis.
Catalytic transfer of the adenosyl group
In simple terms: The enzyme moves the adenosyl part of ATP onto methionine to make SAM.
The catalytic mechanism involves the transfer of the adenosyl moiety from ATP to the sulfur atom of L-methionine, yielding S-adenosyl-L-methionine and the byproducts phosphate and diphosphate. This reaction proceeds through a pentacoordinate transition state, and the enzyme uses a conserved aspartate residue to stabilize the methionine sulfur. Mutagenesis and computational studies have identified key electrostatic interactions that lower the activation energy and enhance catalytic efficiency.
Product release and reaction cycle
In simple terms: The enzyme releases SAM and the leftover phosphate pieces, then resets for another round.
Following catalysis, SAM is released first, followed by phosphate and diphosphate. The enzyme can undergo multiple turnover cycles, and its activity is regulated by the availability of methionine and ATP. In liver, MAT1A is the predominant isoform, while MAT2A is induced during proliferation and in cancer.
Regulation by MAT2B and metabolic state
In simple terms: A helper protein called MAT2B can turn the enzyme's activity up or down.
MAT2B, a regulatory subunit, associates with MAT2A and modulates its activity in response to cellular methionine and SAM levels. MAT2B can stabilize MAT2A and influence its kinetic properties, linking methionine adenosyltransferase activity to one-carbon metabolism and methylation capacity. Dysregulation of this regulatory interaction contributes to liver cancer and other diseases.
Key Genes Involved in GO:0004478 methionine adenosyltransferase activity
The following genes encode proteins that carry or regulate methionine adenosyltransferase activity and are central to its biological functions.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MAT1A | Liver-specific catalytic subunit of methionine adenosyltransferase | Downregulated in hepatocellular carcinoma; tumor suppressor-like role |
| MAT2A | Ubiquitous catalytic subunit; primary source of SAM in most tissues | Synthetic lethal target in MTAP-deleted cancers |
| MAT2B | Regulatory subunit that modulates MAT2A activity | Influences SAM levels and cancer cell proliferation |
| GNMT | Glycine N-methyltransferase; consumes SAM | Linked to liver disease and methylation balance |
| MTHFR | Regenerates methionine from homocysteine | Polymorphisms affect SAM availability |
| MTR | Methionine synthase; remethylates homocysteine | One-carbon metabolism crosstalk |
| BHMT | Betaine-homocysteine methyltransferase | Alternative methionine synthesis in liver |
| CBS | Cystathionine beta-synthase; transsulfuration | Uses SAM as activator |
| PRMT5 | Protein arginine methyltransferase; depends on SAM | Splicing regulation; target in MTAP-deleted cancers |
| RIOK1 | Kinase involved in splicing; synthetic lethal with MTAP loss | Target in MTAP-deleted tumors |
| MTAP | Methylthioadenosine phosphorylase; frequently deleted in cancer | Biomarker for MAT2A inhibitor sensitivity |
| PHB1 | Prohibitin 1; interacts with MAT1A | Defends against liver cancer metastasis |
| PD-L1 | Immune checkpoint ligand; induced by methionine intervention | Enhances immunotherapy response in osteosarcoma |
| MAT2A (atherosclerosis) | Epigenetic reprogramming in macrophages | Promotes plaque vulnerability |
| SAM (metabolite) | Universal methyl donor | Central to methylation and polyamine synthesis |
| SAH | S-adenosylhomocysteine; product of methylation | Inhibits transmethylation when accumulated |
| Methionine | Substrate for methionine adenosyltransferase | Dietary restriction affects SAM levels |
How Is methionine adenosyltransferase activity Regulated?
Methionine adenosyltransferase activity is regulated at multiple levels. MAT1A and MAT2A expression is controlled by promoters responsive to methionine, SAM, and growth factors. MAT2B modulates MAT2A activity and stability. SAM itself feedback-inhibits the enzyme, while methionine availability and one-carbon metabolites influence flux. In cancer, MAT2A is induced by proliferation signals and loss of MAT1A. In macrophages, MAT2A expression is linked to epigenetic reprogramming in atherosclerosis.
methionine adenosyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MAT1A | Hepatocellular carcinoma, liver injury | MAT1A knockout mouse; liver-specific KO |
| MAT2A | MTAP-deleted cancers, atherosclerosis | MAT2A conditional KO; MTAP-deleted cell lines |
| MAT2B | Cancer cell proliferation | MAT2B knockout or knockdown cells |
| PRMT5 | Splicing defects in MTAP-deleted tumors | PRMT5 KO; splicing reporter assays |
| PD-L1 | Osteosarcoma immunotherapy response | PD-L1 knock-in; syngeneic tumor models |
Liver cancer and liver injury
MAT1A downregulation and MAT2A upregulation are hallmarks of hepatocellular carcinoma and are associated with poor prognosis. Prohibitin 1 and MAT1A cooperate to defend against primary and secondary liver cancer metastasis. SAM depletion contributes to liver injury, steatosis, and carcinogenesis.
MTAP-deleted cancers
MTAP deletions occur in many cancers and create a dependency on MAT2A for SAM supply. MAT2A inhibition blocks growth of MTAP-deleted cancer cells by reducing PRMT5-dependent mRNA splicing and inducing DNA damage. This synthetic lethal interaction is a promising therapeutic strategy.
Osteosarcoma and immunotherapy
In MTAP-deleted osteosarcoma, methionine intervention induces PD-L1 expression and enhances immune checkpoint therapy response. This links methionine adenosyltransferase activity to tumor immunology.
Atherosclerosis
MAT2A promotes atherosclerotic plaque vulnerability by mediating epigenetic reprogramming of macrophages. This highlights a role for methionine adenosyltransferase activity beyond cancer.
From methionine adenosyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does MAT2A loss selectively kill MTAP-deleted cancer cells? | MAT2A knockout in MTAP-deleted vs. wild-type cell lines |
| What is the role of MAT1A in liver cancer metastasis? | Liver-specific MAT1A knockout mouse |
| How does MAT2B regulate MAT2A activity? | MAT2B point mutations or knockout cells |
| Can methionine intervention enhance immunotherapy? | MTAP-deleted osteosarcoma mouse models with PD-L1 knock-in |
| Does MAT2A promote atherosclerosis? | Macrophage-specific MAT2A knockout in ApoE-/- mice |
| What electrostatic interactions enhance catalysis? | Engineered MAT variants with point mutations |
How to Study the methionine adenosyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS metabolomics | SAM, SAH, methionine levels | Assessing pathway flux and inhibitor effects |
| CRISPR knockout screens | Gene essentiality and synthetic lethality | Identifying MAT2A dependencies |
| RNA-seq | Gene expression and splicing changes | Evaluating PRMT5-dependent splicing |
| Western blot | Protein expression and methylation marks | Validating MAT2A knockdown |
| Enzyme activity assay | SAM production rate | Kinetic characterization of MAT variants |
| Immunohistochemistry | MAT1A/MAT2A tissue expression | Liver cancer prognosis studies |
| Flow cytometry | PD-L1 surface expression | Immunotherapy response assessment |
| Mouse tumor models | Tumor growth and metastasis | Preclinical testing of MAT2A inhibitors |
Enzymatic activity assays
Methionine adenosyltransferase activity is measured by monitoring SAM production using HPLC, LC-MS, or coupled enzyme assays. These methods quantify kinetic parameters and inhibitor efficacy.
CRISPR screening and functional genomics
Genome-wide CRISPR knockout screens identify genes that modulate sensitivity to MAT2A inhibitors, revealing synthetic lethal interactions such as MTAP deletion. These screens are powerful for target discovery.
RNA-seq and splicing analysis
MAT2A inhibition alters PRMT5-dependent mRNA splicing, which can be assessed by RNA-seq and splicing-sensitive reporters. This links methionine adenosyltransferase activity to post-transcriptional regulation.
Metabolomics and proteomics
LC-MS-based metabolomics quantifies SAM, SAH, methionine, and related metabolites. Proteomics can assess global methylation changes and PRMT5 substrate modification.
How CRISPR Can Be Used to Study GO:0004478 methionine adenosyltransferase activity
Knockout
CRISPR knockout of MAT2A in MTAP-deleted cancer cells induces DNA damage and reduces viability, validating synthetic lethality. MAT1A knockout in mouse liver promotes tumorigenesis and metastasis. These models are essential for causal inference.
Point Mutation
Point mutations in the MAT2A active site can abolish catalytic activity or alter substrate specificity, enabling structure-function studies. Such mutants help identify key electrostatic interactions required for catalysis.
Knock-in
Knock-in of tagged MAT2A (e.g., HA or GFP) allows tracking of protein localization and interactions in live cells. Knock-in of disease-associated variants can model human mutations affecting methionine adenosyltransferase activity.
Overexpression
Overexpression of MAT2A or MAT1A in cell lines increases SAM levels and can drive proliferation or epigenetic changes. Overexpression models are useful for studying gain-of-function effects in cancer and atherosclerosis.
How EDITGENE Supports methionine adenosyltransferase activity Research
Researchers studying methionine adenosyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in SAM metabolism, methylation, or disease. EDITGENE provides CRISPR-based cell models and screening services to accelerate this discovery.
Contact EDITGENE today to design your custom CRISPR model for methionine adenosyltransferase activity research.
Frequently Asked Questions About methionine adenosyltransferase activity
What is methionine adenosyltransferase activity?
It is the enzyme activity (GO:0004478) that catalyzes the reaction ATP + L-methionine + H2O = phosphate + diphosphate + S-adenosyl-L-methionine, producing the universal methyl donor SAM.
What genes are involved in methionine adenosyltransferase activity?
The main human genes are MAT1A, MAT2A, and MAT2B, which encode catalytic and regulatory subunits.
Why is MAT2A a cancer target?
MAT2A is synthetically lethal with MTAP deletion, and its inhibition blocks growth of MTAP-deleted cancer cells by reducing PRMT5-dependent splicing and inducing DNA damage.
What diseases are linked to methionine adenosyltransferase activity?
Liver cancer, MTAP-deleted cancers, osteosarcoma, and atherosclerosis are linked to dysregulation of this activity.
How is methionine adenosyltransferase activity measured?
It is measured by enzymatic assays that quantify SAM production using HPLC or LC-MS.
What is the role of MAT2B?
MAT2B is a regulatory subunit that modulates MAT2A activity and stability, influencing SAM levels.
Can CRISPR be used to study methionine adenosyltransferase activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect gene function in this pathway.
What is the relationship between MAT2A and PRMT5?
MAT2A provides SAM for PRMT5-mediated methylation, and MAT2A inhibition impairs PRMT5-dependent mRNA splicing.
Is methionine adenosyltransferase activity involved in atherosclerosis?
Yes, MAT2A promotes atherosclerotic plaque vulnerability by mediating epigenetic reprogramming of macrophages.
What model systems are used to study methionine adenosyltransferase activity?
Common models include liver-specific MAT1A knockout mice, MAT2A knockout cell lines, and MTAP-deleted cancer models.
Conclusion
Methionine adenosyltransferase activity (GO:0004478) is a fundamental molecular function that produces SAM, the universal methyl donor, and is central to one-carbon metabolism, methylation, and polyamine synthesis. Its dysregulation is implicated in liver cancer, MTAP-deleted cancers, osteosarcoma, and atherosclerosis, making it a high-value therapeutic target. CRISPR-based models and functional genomics are essential tools for dissecting its causal roles and for developing targeted therapies.
References
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- 2. Kalev P et al.. 2021. MAT2A Inhibition Blocks the Growth of MTAP-Deleted Cancer Cells by Reducing PRMT5-Dependent mRNA Splicing and Inducing DNA Damage.. Cancer Cell 39(2):209-224.e11 PMID: 33450196
- 3. Lin W et al.. 2024. Engineering of Methionine Adenosyltransferase Reveals Key Roles of Electrostatic Interactions in Enhanced Catalytic Activity.. Appl Biochem Biotechnol 196(6):3246-3259 PMID: 37642924
- 4. Marjon K et al.. 2016. MTAP Deletions in Cancer Create Vulnerability to Targeting of the MAT2A/PRMT5/RIOK1 Axis.. Cell Rep 15(3):574-587 PMID: 27068473
- 5. Fan W et al.. 2024. Hepatic prohibitin 1 and methionine adenosyltransferase α1 defend against primary and secondary liver cancer metastasis.. J Hepatol 80(3):443-453 PMID: 38086446
- 6. Mu H et al.. 2025. Methionine intervention induces PD-L1 expression to enhance the immune checkpoint therapy response in MTAP-deleted osteosarcoma.. Cell Rep Med 6(3):101977 PMID: 39983717
- 7. Pajares MA et al.. 2011. Methionine adenosyltransferase (s-adenosylmethionine synthetase).. Adv Enzymol Relat Areas Mol Biol 78:449-521 PMID: 22220481
- 8. Du Z et al.. 2025. MAT2A promotes atherosclerotic plaque vulnerability by mediating epigenetic reprogramming of macrophages.. Nat Commun 16(1):11168 PMID: 41402252
