GO:0030735 carnosine N-methyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0030735 carnosine N-methyltransferase activity catalyzes the S-adenosyl-L-methionine-dependent methylation of carnosine to anserine, producing S-adenosyl-L-homocysteine and H+.
• The enzyme is a histidine N1-position-specific methyltransferase, and in chicken it was molecularly identified as histamine N-methyltransferase-like protein (HNMT-like).
• In humans, the orthologous enzyme is encoded by C9orf41 (UPF0586), which produces anserine and is also known as CARNMT1.
• CARNMT1 targets C3H zinc finger proteins and modulates RNA metabolism, linking this methylation activity to gene expression regulation.
• The yeast putative carnosine N-methyltransferase has been structurally and biochemically characterized, revealing substrate recognition determinants.
• This activity is relevant to muscle physiology, oxidative stress, and emerging roles in macrophage ferroptosis and host-pathogen interactions.
Description
Carnosine N-methyltransferase activity (GO:0030735) is a molecular function defined as the catalysis of the reaction: S-adenosyl-L-methionine + carnosine = S-adenosyl-L-homocysteine + anserine + H+. This methylation reaction converts the dipeptide carnosine (beta-alanyl-L-histidine) into its N1-methylated derivative anserine (beta-alanyl-1-methyl-L-histidine), using S-adenosyl-L-methionine (SAM) as the methyl donor. The enzyme responsible was first molecularly identified in chicken as a histamine N-methyltransferase-like protein (HNMT-like), establishing that carnosine N-methyltransferase belongs to the class of histidine N1-position-specific methyltransferases. In humans, the orthologous protein is encoded by C9orf41 (also known as UPF0586 or CARNMT1), which was shown to be an anserine-producing methyltransferase. The importance of GO:0030735 extends beyond a single metabolic conversion. Anserine and its precursor carnosine are abundant in skeletal muscle and brain, where they act as buffers and antioxidants, and their methylation status influences their physiological properties. More recently, CARNMT1, the human enzyme carrying this activity, was found to target C3H zinc finger proteins and to modulate RNA metabolism, revealing a role in post-translational regulation of RNA-binding proteins. Furthermore, a Pseudomonas aeruginosa quorum-sensing metabolite was shown to manipulate macrophage ferroptosis through a methylation pathway involving this enzyme, connecting GO:0030735 to host-pathogen interactions and cell death regulation. For researchers, GO:0030735 provides a precise functional annotation for studies of histidine methylation, dipeptide metabolism, and RNA biology. The availability of structural and biochemical data on the yeast and chicken enzymes, together with human cell models, makes it a tractable target for CRISPR-based functional genomics.
carnosine N-methyltransferase activity At A Glance
| GO ID | GO:0030735 |
|---|---|
| GO term | carnosine N-methyltransferase activity |
| Ontology | molecular_function |
| Synonym | S-adenosyl-L-methionine:carnosine N-methyltransferase activity |
| Definition | Catalysis of the reaction: S-adenosyl-L-methionine + carnosine = S-adenosyl-L-homocysteine + anserine + H+. |
| Major function | Methylation of carnosine to anserine using SAM as methyl donor |
| Enzyme class | Methyltransferase (histidine N1-position-specific) |
| Representative genes | C9orf41 (CARNMT1) in human; HNMT-like in chicken; putative carnosine N-methyltransferase in yeast |
| Substrates | Carnosine (beta-alanyl-L-histidine) and S-adenosyl-L-methionine |
| Products | Anserine (beta-alanyl-1-methyl-L-histidine), S-adenosyl-L-homocysteine, H+ |
What Is GO:0030735?
In simple terms, GO:0030735 describes the enzyme activity that attaches a methyl group to carnosine, turning it into anserine. Chemically, it catalyzes the transfer of a methyl group from S-adenosyl-L-methionine (SAM) to the N1 position of the histidine ring of carnosine, yielding S-adenosyl-L-homocysteine (SAH), anserine, and a proton (H+). This is a methyltransferase activity that is specific for the N1 position of the histidine imidazole ring, distinguishing it from other histidine methyltransferases. The reaction is part of histidine-containing dipeptide metabolism and represents a key step in the biosynthesis of anserine from carnosine.
Why Is carnosine N-methyltransferase activity Important in Cell Biology?
GO:0030735 is important because it defines the only known enzymatic route for anserine biosynthesis from carnosine in vertebrates, and it connects histidine dipeptide metabolism to broader cellular processes such as RNA metabolism and cell death regulation. Anserine and carnosine are abundant in skeletal muscle and brain, where they contribute to pH buffering and antioxidant defense, and their relative levels depend on this methylation activity. The human enzyme CARNMT1 has been shown to methylate C3H zinc finger proteins, thereby influencing RNA metabolism, which places GO:0030735 in the context of post-translational regulation of RNA-binding proteins. In infection biology, a Pseudomonas aeruginosa quorum-sensing metabolite was reported to manipulate macrophage ferroptosis through a methylation pathway involving this activity, highlighting its role in host-pathogen interactions. Thus, GO:0030735 is a focal point for studies of muscle physiology, neurobiology, RNA biology, and infectious disease.
• Defines the biosynthetic step that converts carnosine to anserine, a major histidine dipeptide in muscle and brain.
• Provides a molecular handle on histidine N1-methylation, a modification increasingly recognized in protein and metabolite regulation.
• Links to RNA metabolism through CARNMT1-mediated methylation of C3H zinc finger proteins.
• Implicated in macrophage ferroptosis during Pseudomonas aeruginosa infection, suggesting a role in innate immunity.
• Relevant to muscle physiology and exercise biology because anserine and carnosine are key intramuscular buffers and antioxidants.
• Offers a target for structural and mechanistic studies of methyltransferases, with yeast and chicken enzymes already characterized.
• Supports the development of CRISPR knockout and knock-in models to dissect gene function in human cells.
• May inform research on metabolic reprogramming in cancer and neurodegeneration through dipeptide metabolism.
• Enables comparative genomics and evolutionary studies of histidine methyltransferases across species.
• Facilitates drug discovery efforts targeting methylation pathways in infection and inflammation.
Molecular Mechanism of carnosine N-methyltransferase activity
Substrate recognition and binding
In simple terms: The enzyme first grabs carnosine and SAM, the methyl donor, in a precise orientation.
Carnosine N-methyltransferase specifically recognizes carnosine (beta-alanyl-L-histidine) and S-adenosyl-L-methionine (SAM) as substrates. Structural and biochemical studies of the putative yeast carnosine N-methyltransferase have revealed the substrate recognition mechanism, showing how the enzyme positions the imidazole ring of carnosine for N1-specific methylation. The chicken enzyme, identified as HNMT-like protein, exhibits high specificity for carnosine over other histidine-containing dipeptides, and its activity depends on the presence of the carnosine dipeptide backbone. In humans, C9orf41 (CARNMT1) was shown to produce anserine, confirming that it recognizes carnosine as a substrate.
Catalytic methyl transfer
In simple terms: The enzyme moves a methyl group from SAM onto the carnosine molecule.
The catalytic step involves transfer of the methyl group from SAM to the N1 position of the histidine imidazole ring of carnosine, generating anserine and S-adenosyl-L-homocysteine (SAH). This reaction is classified as a histidine N1-position-specific methyltransferase activity, and the enzyme does not methylate the N3 position. The reaction also releases a proton (H+), consistent with the GO definition. The use of alternative substrates has been explored to characterize carnosine-methylating enzymes, providing insight into the catalytic mechanism.
Product release and turnover
In simple terms: After the reaction, the enzyme releases anserine and SAH so it can start again.
Following methyl transfer, the enzyme releases anserine, SAH, and H+. Anserine is the N1-methylated derivative of carnosine and is a stable product that can be detected in cells and tissues. SAH is a product and a potential feedback inhibitor of many methyltransferases, and its levels can influence enzyme turnover. The catalytic efficiency of the enzyme may depend on its ability to preserve reactive conformations during catalysis, as suggested by studies on enzyme-catalyzed reactions.
Cofactor and metal requirements
In simple terms: The enzyme uses SAM as a cofactor but does not appear to need metals.
Carnosine N-methyltransferase uses S-adenosyl-L-methionine (SAM) as the methyl donor cofactor. There is no evidence in the provided literature that the enzyme requires metal ions for activity; the reaction is a classic SAM-dependent methyl transfer. The enzyme belongs to the class of SAM-dependent methyltransferases, and its activity can be measured by monitoring the formation of SAH or anserine.
Regulation by substrates and inhibitors
In simple terms: The enzyme's speed can be influenced by how much carnosine and SAM are available.
The activity of carnosine N-methyltransferase is dependent on the availability of carnosine and SAM. Because SAH is a product, it may act as a competitive inhibitor, as is common for methyltransferases. The enzyme's activity can be modulated by alternative substrates, as shown in early characterization studies using carnosine-methylating enzymes. In addition, the human enzyme CARNMT1 targets C3H zinc finger proteins, suggesting that its activity may be regulated by the availability of protein substrates in addition to small-molecule substrates.
Key Genes Involved in GO:0030735 carnosine N-methyltransferase activity
The following genes and proteins are directly implicated in carnosine N-methyltransferase activity (GO:0030735) or in its physiological context, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| C9orf41 (CARNMT1) | Human anserine-producing methyltransferase; catalyzes carnosine N-methylation | Central enzyme for GO:0030735 in human cells; target for knockout and knock-in studies |
| HNMT-like (chicken) | Chicken carnosine N-methyltransferase; molecularly identified as histamine N-methyltransferase-like protein | Provides the first molecular identification of the enzyme and substrate specificity data |
| Putative yeast carnosine N-methyltransferase | Yeast enzyme with structural and biochemical characterization | Model for substrate recognition and catalytic mechanism |
| HNMT | Histamine N-methyltransferase; related methyltransferase with overlapping substrate chemistry | Comparative studies of histidine methylation and enzyme specificity |
| C3H zinc finger proteins | Protein substrates methylated by CARNMT1; involved in RNA metabolism | Link between GO:0030735 and RNA biology |
| HDAC1 | Histone deacetylase 1; used in proteomics-based trapping studies | Methodological relevance for substrate profiling of methyltransferases |
| SAM (S-adenosyl-L-methionine) | Methyl donor cofactor for the reaction | Essential cofactor; its availability affects enzyme activity |
| SAH (S-adenosyl-L-homocysteine) | Product and potential feedback inhibitor | Used to monitor enzyme activity and inhibition |
| Carnosine | Substrate dipeptide (beta-alanyl-L-histidine) | Substrate for the reaction; its levels influence anserine production |
| Anserine | Product dipeptide (beta-alanyl-1-methyl-L-histidine) | Readout of enzyme activity; physiological buffer and antioxidant |
| UPF0586 | Alternative name for C9orf41 in humans | Used in early identification of the anserine-producing methyltransferase |
| Pseudomonas aeruginosa quorum-sensing metabolite | Bacterial metabolite that manipulates macrophage ferroptosis via methylation | Connects GO:0030735 to host-pathogen interactions |
| Macrophage ferroptosis pathway | Cell death pathway influenced by methylation | Disease-relevant context for the enzyme |
| Actin-methylating enzymes | Related methyltransferases used in substrate characterization | Comparative enzymology of methyltransferases |
| Histidine N1-methyltransferases | Enzyme family to which carnosine N-methyltransferase belongs | Family-level studies of substrate specificity |
| RNA metabolism factors | Proteins and pathways affected by CARNMT1-mediated methylation | Functional readout of GO:0030735 in RNA biology |
How Is carnosine N-methyltransferase activity Regulated?
The activity of carnosine N-methyltransferase (GO:0030735) is primarily regulated by substrate availability, particularly the concentrations of carnosine and S-adenosyl-L-methionine (SAM). Product inhibition by S-adenosyl-L-homocysteine (SAH) may also modulate enzyme turnover, as is common for SAM-dependent methyltransferases. In humans, CARNMT1 targets C3H zinc finger proteins, and its activity may be influenced by the availability of these protein substrates and their localization. Additionally, a Pseudomonas aeruginosa quorum-sensing metabolite was shown to manipulate macrophage ferroptosis through a methylation pathway, suggesting that bacterial signals can indirectly affect this activity during infection. No direct allosteric or post-translational regulation of the enzyme is described in the provided literature, so the main known regulatory inputs are substrate supply and product feedback.
carnosine N-methyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| C9orf41 (CARNMT1) | RNA metabolism and zinc finger protein regulation | Knockout and knock-in human cell lines |
| C9orf41 (CARNMT1) | Macrophage ferroptosis during Pseudomonas aeruginosa infection | Macrophage cell models with KO or overexpression |
| HNMT-like (chicken) | Histidine dipeptide metabolism | Chicken cell lines or primary cells |
| Putative yeast carnosine N-methyltransferase | Substrate recognition and catalysis | Yeast knockout and point-mutant strains |
| C3H zinc finger proteins | RNA metabolism | CRISPR knockout of C3H zinc finger genes |
Infection and macrophage ferroptosis
A Pseudomonas aeruginosa quorum-sensing metabolite was reported to manipulate macrophage ferroptosis through a methylation pathway. This connects carnosine N-methyltransferase activity (GO:0030735) to host-pathogen interactions and innate immune cell death. The study suggests that bacterial signals can alter methylation-dependent processes in macrophages, potentially affecting the outcome of infection. Researchers can use this link to explore whether modulating GO:0030735 activity influences ferroptosis and bacterial clearance.
RNA metabolism and zinc finger protein regulation
CARNMT1, the human enzyme carrying carnosine N-methyltransferase activity, targets C3H zinc finger proteins and modulates RNA metabolism. Dysregulation of RNA metabolism is a hallmark of many diseases, including cancer and neurodegeneration, although direct disease associations for CARNMT1 mutations are not established in the provided literature. This section highlights the potential for future studies linking GO:0030735 to RNA-related pathologies.
Muscle physiology and dipeptide metabolism
Anserine and carnosine are abundant in skeletal muscle, where they contribute to pH buffering and antioxidant defense. The conversion of carnosine to anserine by GO:0030735 affects the relative levels of these dipeptides, which may influence muscle function and exercise performance. While direct disease associations are not described in the provided literature, altered dipeptide metabolism has been studied in muscle-related conditions.
From carnosine N-methyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of C9orf41 (CARNMT1) reduce anserine production? | CRISPR knockout human cell line |
| Which residues are required for carnosine binding? | Point-mutation knock-in of catalytic residues |
| Can tagged CARNMT1 be used to profile interacting proteins? | Knock-in of epitope tag at endogenous locus |
| Does overexpression of CARNMT1 alter RNA metabolism? | Overexpression cell model |
| Does the enzyme modulate macrophage ferroptosis? | Knockout or overexpression in macrophages |
| Can yeast be used to study substrate specificity? | Yeast knockout and point mutants |
How to Study the carnosine N-methyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS/MS | Anserine and SAH levels | Enzyme activity in cell lysates |
| Proteomics-based trapping | Enzyme-substrate complexes | Substrate profiling of methyltransferases |
| RNA-seq | RNA expression and stability changes | Functional impact of CARNMT1 modulation |
| Western blot | Protein expression of CARNMT1 and substrates | Validation of knockout or overexpression |
| Immunoprecipitation | Protein-protein interactions | Identification of C3H zinc finger protein interactions |
| Site-directed mutagenesis | Catalytic residue requirements | Mechanistic studies of the enzyme |
| Enzyme kinetics | Km, Vmax, and inhibition parameters | Characterization of substrate specificity |
| CRISPR screening | Gene essentiality and pathway interactions | Functional genomics of methylation pathways |
Enzymatic activity assays
Carnosine N-methyltransferase activity can be measured by monitoring the formation of anserine or S-adenosyl-L-homocysteine (SAH) using chromatographic or mass spectrometry methods. Early studies used alternative substrates to characterize carnosine-methylating enzymes, providing a basis for activity assays. These assays are essential for validating CRISPR knockout or point-mutation models.
Proteomics and substrate trapping
Proteomics-based trapping with inactive mutants can be used to profile substrates of methyltransferases, as demonstrated for histone deacetylase 1. Similar approaches could be applied to CARNMT1 to identify protein substrates such as C3H zinc finger proteins. This method combines immunoprecipitation with mass spectrometry to capture enzyme-substrate complexes.
RNA metabolism readouts
Because CARNMT1 targets C3H zinc finger proteins and modulates RNA metabolism, RNA-seq and related RNA profiling methods can be used to assess the functional consequences of altering GO:0030735 activity. Changes in RNA stability, splicing, or translation can be monitored in knockout or overexpression models.
Structural and biochemical characterization
Structural studies of the yeast putative carnosine N-methyltransferase have revealed substrate recognition mechanisms. Biochemical assays with purified enzymes, including point mutants, can define catalytic residues and cofactor requirements. These methods provide mechanistic insight into GO:0030735.
How CRISPR Can Be Used to Study GO:0030735 carnosine N-methyltransferase activity
Knockout
CRISPR knockout of C9orf41 (CARNMT1) can abolish carnosine N-methyltransferase activity, leading to reduced anserine levels and accumulation of carnosine. Such models are useful to study the physiological consequences of loss of GO:0030735, including effects on RNA metabolism and macrophage ferroptosis. Knockout cell lines can be validated by measuring anserine production and by Western blotting for the enzyme.
Point Mutation
Point mutations in catalytic residues of carnosine N-methyltransferase can be introduced to dissect the mechanism of methyl transfer. For example, mutations in the SAM-binding pocket or carnosine-binding site can distinguish substrate binding from catalysis. These models are valuable for structure-function studies and for validating inhibitor specificity.
Knock-in
Knock-in of epitope tags or fluorescent reporters at the endogenous C9orf41 locus allows for tracking of enzyme expression, localization, and interaction partners. Tagged knock-in models can be used in proteomics-based trapping experiments to identify substrates such as C3H zinc finger proteins. This approach preserves endogenous regulation of the gene.
Overexpression
Overexpression of CARNMT1 or its orthologs can increase anserine production and enhance methylation of target proteins. Overexpression models are useful to study gain-of-function effects on RNA metabolism and cell death pathways. They can also be used to produce recombinant enzyme for biochemical assays.
How EDITGENE Supports carnosine N-methyltransferase activity Research
Researchers studying carnosine N-methyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in a specific phenotype, such as anserine production, RNA metabolism, or macrophage ferroptosis. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models that enable such causal inferences.
Contact EDITGENE today to design your custom CRISPR model for carnosine N-methyltransferase activity research.
Frequently Asked Questions About carnosine N-methyltransferase activity
What is carnosine N-methyltransferase activity?
It is the enzyme activity defined by GO:0030735 that catalyzes the methylation of carnosine to anserine using S-adenosyl-L-methionine as the methyl donor.
What genes are involved in carnosine N-methyltransferase activity?
The main gene in humans is C9orf41 (CARNMT1); in chicken, the HNMT-like gene encodes the enzyme, and yeast has a putative carnosine N-methyltransferase.
What is the reaction catalyzed by GO:0030735?
The reaction is: S-adenosyl-L-methionine + carnosine = S-adenosyl-L-homocysteine + anserine + H+.
What is the difference between carnosine and anserine?
Carnosine is beta-alanyl-L-histidine, while anserine is its N1-methylated derivative, beta-alanyl-1-methyl-L-histidine, produced by GO:0030735.
Which enzyme produces anserine in humans?
The human enzyme C9orf41 (CARNMT1) is an anserine-producing methyltransferase that carries out GO:0030735.
Is carnosine N-methyltransferase involved in disease?
It has been linked to macrophage ferroptosis during Pseudomonas aeruginosa infection and to RNA metabolism through methylation of C3H zinc finger proteins.
How can I study carnosine N-methyltransferase activity in the lab?
You can use enzymatic assays measuring anserine or SAH, CRISPR knockout or overexpression models, and proteomics-based substrate trapping.
What is the role of CARNMT1 in RNA metabolism?
CARNMT1 targets C3H zinc finger proteins and modulates RNA metabolism, linking GO:0030735 to post-translational regulation of RNA-binding proteins.
Can CRISPR be used to study GO:0030735?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models can be used to dissect the function of carnosine N-methyltransferase activity.
What model organisms are used to study carnosine N-methyltransferase?
Chicken and yeast are established models, with the chicken enzyme identified as HNMT-like and the yeast enzyme structurally characterized.
Conclusion
GO:0030735 carnosine N-methyltransferase activity defines a specific histidine N1-methylation reaction that converts carnosine to anserine, with the human enzyme C9orf41 (CARNMT1) playing a central role. Beyond dipeptide metabolism, this activity has been linked to RNA metabolism through C3H zinc finger protein methylation and to macrophage ferroptosis during bacterial infection. The availability of structural, biochemical, and CRISPR-based tools makes GO:0030735 a tractable target for functional studies in muscle physiology, RNA biology, and host-pathogen interactions.
References
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- 2. Drozak J et al.. 2013. Molecular identification of carnosine N-methyltransferase as chicken histamine N-methyltransferase-like protein (hnmt-like).. PLoS One 8(5):e64805 PMID: 23705015
- 3. Jia T et al.. 2025. A Pseudomonas aeruginosa quorum-sensing metabolite manipulates macrophage ferroptosis through a methylation pathway.. Nat Commun 16(1):9992 PMID: 41233346
- 4. Drozak J et al.. 2015. UPF0586 Protein C9orf41 Homolog Is Anserine-producing Methyltransferase.. J Biol Chem 290(28):17190-205 PMID: 26001783
- 5. Shimazu T et al.. 2023. Histidine N1-position-specific methyltransferase CARNMT1 targets C3H zinc finger proteins and modulates RNA metabolism.. Genes Dev 37(15-16):724-742 PMID: 37612136
- 6. Herath KE et al.. 2023. Proteomics-based trapping with single or multiple inactive mutants reproducibly profiles histone deacetylase 1 substrates.. J Proteomics 274:104807 PMID: 36587730
- 7. Raghavan M et al.. 1992. The use of alternative substrates in the characterization of actin-methylating and carnosine-methylating enzymes.. Eur J Biochem 210(1):311-8 PMID: 1446680
- 8. Yang M et al.. 2025. The Ability of Enzymes to Preserve Reactive Conformations During Enzyme-Catalyzed Reactions can be an Important Factor for Efficient Catalysis.. Chemistry 31(49):e01422 PMID: 40810683
