GO:0071265 L-methionine biosynthetic process: Amino Acid Biosynthesis Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0071265 L-methionine biosynthetic process describes the chemical reactions and pathways that form L-methionine, the proteinogenic sulfur-containing amino acid.
• In bacteria such as Escherichia coli, the pathway is a major metabolic engineering target because L-methionine is widely used in animal feed and pharmaceuticals.
• The pathway is tightly regulated by feedback inhibition and transcriptional control, and module genetic perturbations alter local metabolic responses.
• L-Methionine is the direct precursor of S-adenosyl-L-methionine (SAM), the principal methyl donor in cells.
• Systems metabolic engineering and CRISPR-based genome editing are used to improve L-methionine production in microbial cell factories.
• Studying this process requires combining genetics, metabolomics, and flux analysis to resolve pathway bottlenecks.
Description
GO:0071265 L-methionine biosynthetic process is the biological process by which cells synthesize L-methionine, the L-enantiomer of (2S)-2-amino-4-(methylsulfanyl)butanoic acid. L-Methionine is an essential amino acid for humans and animals and a key precursor of S-adenosyl-L-methionine (SAM), the major methyl donor in transmethylation reactions. Because of its industrial importance in animal feed and pharmaceuticals, the pathway has been extensively studied in microorganisms and plants. The process is tightly regulated at both the transcriptional and enzymatic levels, and its manipulation is a central goal of metabolic engineering. Understanding the genes, enzymes, and regulatory nodes of L-methionine biosynthesis is therefore critical for both fundamental biology and biotechnological applications.
L-methionine biosynthetic process At A Glance
| GO ID | GO:0071265 |
|---|---|
| GO term | L-methionine biosynthetic process |
| Ontology | biological_process |
| Synonym | L-methionine anabolism, L-methionine biosynthesis, L-methionine formation, L-methionine synthesis |
| Major function | Synthesis of L-methionine from precursor metabolites and sulfur sources |
| Key precursor | Homocysteine (methylated to methionine) |
| Key cofactor | S-adenosyl-L-methionine (SAM) as methyl donor |
| Representative organisms | Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, plants |
What Is GO:0071265?
The L-methionine biosynthetic process (GO:0071265) encompasses the chemical reactions and pathways that result in the formation of L-methionine, the L-enantiomer of (2S)-2-amino-4-(methylsulfanyl)butanoic acid. It includes the de novo biosynthesis of the methionine carbon skeleton and the sulfur assimilation steps that supply the sulfur atom, as well as the terminal methylation of homocysteine to methionine.
Why Is L-methionine biosynthetic process Important in Cell Biology?
L-Methionine is an essential amino acid and a precursor of SAM, the universal methyl donor, so its biosynthesis is fundamental to cellular metabolism, protein synthesis, and epigenetic regulation. In biotechnology, L-methionine is a high-value product used in animal feed and as a pharmaceutical intermediate, making the pathway a prime target for metabolic engineering. In agriculture, methionine supplementation is critical for poultry and livestock nutrition. Thus, understanding GO:0071265 has broad implications for nutrition, medicine, and industrial microbiology.
• L-Methionine is an essential amino acid required for protein synthesis in humans and animals.
• It is the direct precursor of SAM, the primary methyl donor for DNA, RNA, and protein methylation.
• Microbial L-methionine production is an industrial biotechnology target for animal feed additives.
• The pathway is a model system for studying sulfur assimilation and metabolic regulation.
• Dysregulation of methionine metabolism is linked to cancer, neurological disorders, and cardiovascular disease.
• CRISPR-based engineering of the pathway enables antibiotic-free high-level production in E. coli.
• Relative bioavailability studies of L-methionine inform poultry nutrition.
• Systems metabolic engineering approaches integrate omics data to optimize the pathway.
What Happens During L-methionine biosynthetic process?
Sulfur assimilation and activation
In simple terms: Cells first take up sulfate or other sulfur sources and convert them into a usable form.
In many microorganisms, sulfate is reduced to sulfide and then incorporated into O-acetyl-L-homoserine or O-succinyl-L-homoserine to form homocysteine, the immediate precursor of methionine. This step is energy-dependent and tightly regulated.
Homocysteine formation
In simple terms: The carbon skeleton and sulfur are joined to make homocysteine.
Homocysteine is synthesized from aspartate-derived intermediates via the transsulfuration pathway or direct sulfhydrylation, depending on the organism. In E. coli, the metA and metB genes encode enzymes that catalyze these reactions.
Methylation of homocysteine to methionine
In simple terms: A methyl group is added to homocysteine to produce methionine.
The final step is catalyzed by methionine synthase (MetH or MetE), which transfers a methyl group from 5-methyltetrahydrofolate or from SAM via a cobalamin-dependent mechanism. This step is the terminal and often rate-limiting reaction of the pathway.
Regulation and feedback control
In simple terms: The cell senses methionine levels and adjusts the pathway to avoid waste.
The pathway is regulated by feedback inhibition of the first committed enzyme and by transcriptional attenuation via the met regulon. Module genetic perturbations in the L-methionine biosynthetic pathway alter local metabolic responses, as shown in E. coli.
Integration with SAM metabolism
In simple terms: Methionine is converted into SAM, which feeds back into the pathway.
SAM is synthesized from methionine and ATP by methionine adenosyltransferase; SAM then serves as a methyl donor and regulates methionine biosynthesis through feedback loops. This interconnectivity makes the pathway a hub of one-carbon metabolism.
Key Genes Involved in GO:0071265 L-methionine biosynthetic process
The following genes and enzymes are central to the L-methionine biosynthetic process across model organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| metA | Homoserine O-succinyltransferase | First committed step in E. coli methionine biosynthesis |
| metB | Cystathionine gamma-synthase | Catalyzes homocysteine formation |
| metC | Cystathionine beta-lyase | Involved in transsulfuration |
| metE | Cobalamin-independent methionine synthase | Terminal methylation of homocysteine |
| metH | Cobalamin-dependent methionine synthase | Alternative terminal methylation |
| metK | S-adenosylmethionine synthetase | Converts methionine to SAM |
| metF | 5,10-methylenetetrahydrofolate reductase | Supplies methyl groups for methionine synthesis |
| metJ | Transcriptional repressor | Regulates met regulon in response to SAM |
| metR | Transcriptional activator | Activates met genes under limiting methionine |
| cysE | Serine acetyltransferase | Provides O-acetylserine for cysteine and methionine |
| cysK | Cysteine synthase | Links cysteine and methionine metabolism |
| hom | Homoserine dehydrogenase | Supplies homoserine for methionine biosynthesis |
| thrA | Aspartokinase-homoserine dehydrogenase | Branched pathway regulation |
| lysC | Aspartokinase | Regulates aspartate family amino acids |
| gcvH | Glycine cleavage system H protein | One-carbon supply for methionine |
| folD | Bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase | One-carbon metabolism |
| sahH | S-adenosylhomocysteine hydrolase | Recycles homocysteine from SAM |
How Is L-methionine biosynthetic process Regulated?
The L-methionine biosynthetic process is regulated at multiple levels. In E. coli, the met regulon is controlled by the repressor MetJ, which binds SAM as a corepressor, and by the activator MetR, which responds to homocysteine. Feedback inhibition of the first committed enzyme, homoserine O-succinyltransferase (MetA), by methionine and SAM prevents overproduction. Additionally, one-carbon metabolism and SAM availability influence flux through the pathway. In industrial strains, deregulation of these control points is a common engineering strategy.
L-methionine biosynthetic process and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MTR | Homocystinuria, cardiovascular disease | Knockout cell lines and mouse models |
| MTHFR | Neural tube defects, cardiovascular disease | Point mutation knock-in in cell lines |
| MAT1A | Liver cancer, hypermethioninemia | Liver-specific knockout mice |
| CBS | Homocystinuria | Patient-derived iPSCs with CRISPR correction |
| metE/metH | Bacterial pathogenesis | Bacterial knockout libraries for infection studies |
Methionine metabolism and cancer
Altered methionine metabolism is a hallmark of many cancers, which often exhibit methionine dependence. SAM depletion can affect DNA methylation and gene expression, linking the pathway to oncogenesis.
Neurological disorders
Disruptions in methionine and SAM metabolism are associated with neurological conditions such as Alzheimer's disease and depression, where methylation capacity is compromised.
Cardiovascular disease
Elevated homocysteine, a precursor in the methionine biosynthetic pathway, is a risk factor for cardiovascular disease, highlighting the clinical importance of this pathway.
From L-methionine biosynthetic process-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate methionine biosynthesis? | CRISPR knockout in E. coli or mammalian cells |
| Does a point mutation in metA alter feedback inhibition? | Point mutation knock-in |
| Can overexpression of metH increase methionine yield? | Overexpression cell models |
| How does SAM availability affect methionine flux? | Tagged knock-in of SAM sensors |
| What is the role of metJ in global regulation? | Knockout and RNA-seq |
| Can CRISPR library screening identify novel regulators? | Genome-wide CRISPR library screening |
How to Study the L-methionine biosynthetic process Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS/MS metabolomics | Intracellular methionine and SAM levels | Quantifying pathway output |
| RNA-seq | Transcriptional changes in met genes | Regulatory studies |
| 13C flux analysis | Metabolic flux through the pathway | Pathway bottleneck identification |
| Enzyme activity assays | Catalytic activity of pathway enzymes | Biochemical characterization |
| CRISPR knockout screening | Gene essentiality and fitness | Identifying novel regulators |
| Western blot | Protein expression levels | Validating overexpression or knockout |
| Promoter-reporter assays | Transcriptional activity of met promoters | Regulatory element mapping |
Metabolomics and flux analysis
Quantitative metabolomics using LC-MS/MS can measure intracellular methionine and SAM levels, while 13C flux analysis resolves pathway activity.
Transcriptomics and RNA-seq
RNA-seq of knockout or perturbation strains reveals transcriptional changes in the met regulon and related pathways.
Enzyme assays
In vitro enzyme assays for MetA, MetB, and methionine synthase activity provide direct biochemical evidence of pathway function.
CRISPR screening
Genome-wide CRISPR knockout or activation screens can identify genes that modulate methionine biosynthesis or dependence.
How CRISPR Can Be Used to Study GO:0071265 L-methionine biosynthetic process
Knockout
CRISPR knockout of met genes in E. coli or mammalian cells can abolish methionine biosynthesis, creating auxotrophic strains useful for studying pathway essentiality and for selection-based assays.
Point Mutation
Point mutations in metA or metH can relieve feedback inhibition or alter substrate specificity, and are introduced via CRISPR base editing or homology-directed repair to study enzyme kinetics.
Knock-in
Knock-in of tagged met genes (e.g., FLAG or GFP) enables localization and interaction studies, while knock-in of heterologous pathway genes can enhance methionine production.
Overexpression
CRISPR activation (CRISPRa) or plasmid-based overexpression of rate-limiting enzymes such as metH or metE can increase methionine titers in industrial strains.
How EDITGENE Supports L-methionine biosynthetic process Research
Researchers studying L-methionine biosynthetic process-related genes often need to determine whether a candidate gene is causally involved in pathway regulation, flux control, or disease-associated metabolic rewiring. EDITGENE provides end-to-end CRISPR services to generate precisely engineered cell models for such functional studies.
Contact EDITGENE today to design your custom CRISPR model for L-methionine biosynthetic process research.
Frequently Asked Questions About L-methionine biosynthetic process
What is L-methionine biosynthetic process?
It is the biological process (GO:0071265) by which cells synthesize L-methionine from precursor metabolites and sulfur sources.
What genes are involved in L-methionine biosynthetic process?
Key genes include metA, metB, metC, metE, metH, metK, metF, metJ, and metR in E. coli, as well as homologous genes in other organisms.
Why is L-methionine important?
L-Methionine is an essential amino acid and the precursor of SAM, the universal methyl donor, making it critical for protein synthesis and methylation reactions.
How is L-methionine biosynthetic process regulated?
It is regulated by feedback inhibition of the first committed enzyme and by transcriptional regulators such as MetJ and MetR in response to SAM and homocysteine.
What diseases are linked to methionine metabolism?
Altered methionine metabolism is associated with cancer, cardiovascular disease, and neurological disorders.
Can CRISPR be used to study L-methionine biosynthesis?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect the pathway and engineer production strains.
What is the role of SAM in methionine biosynthesis?
SAM is synthesized from methionine and acts as a methyl donor and feedback regulator of the pathway.
How can I measure L-methionine production?
LC-MS/MS metabolomics and enzyme assays are standard methods to quantify methionine and pathway intermediates.
What organisms are used to study L-methionine biosynthesis?
Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, and plants are common model systems.
What is the industrial relevance of L-methionine biosynthesis?
L-Methionine is a high-value animal feed additive and pharmaceutical intermediate, driving metabolic engineering efforts.
Conclusion
GO:0071265 L-methionine biosynthetic process is a fundamental metabolic pathway with broad implications for nutrition, biotechnology, and human health. Its tight regulation and integration with SAM metabolism make it a rich area for both basic and applied research. CRISPR-based tools now enable precise dissection of the pathway and engineering of improved production strains.
References
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- 2. Shen ZY et al.. 2023. Local metabolic response of Escherichia coli to the module genetic perturbations in l-methionine biosynthetic pathway.. J Biosci Bioeng 135(3):217-223 PMID: 36707399
- 4. Cai M et al.. 2023. Microbial production of L-methionine and its precursors using systems metabolic engineering.. Biotechnol Adv 69:108260 PMID: 37739275
- 5. Wang L et al.. 2024. Antibiotic-Free High-Level l-Methionine Production in Engineered Escherichia coli.. J Agric Food Chem 72(46):25791-25800 PMID: 39523813
- 6. Izadi E et al.. 2024. Relative bioavailability of L-methionine and DL-methionine in growing broilers.. Poult Sci 103(12):104311 PMID: 39332342
- 7. Chen H et al.. 2016. Progress in the microbial production of S-adenosyl-L-methionine.. World J Microbiol Biotechnol 32(9):153 PMID: 27465853
- 8. Willke T. 2014. Methionine production--a critical review.. Appl Microbiol Biotechnol 98(24):9893-914 PMID: 25381187
