GO:0004793 threonine aldolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004793 threonine aldolase activity is defined as catalysis of the reaction L-threonine = glycine + acetaldehyde.
• The enzyme is a pyridoxal 5'-phosphate (PLP)-dependent aldolase that cleaves L-threonine into glycine and acetaldehyde.
• Threonine aldolase activity is closely related to serine hydroxymethyltransferase (SHMT) and has been proposed to be identical to SHMT in some organisms.
• In Lactococcus lactis IL1403, excess threonine compared with serine promotes threonine aldolase activity.
• Threonine aldolase activity supplies glycine and one-carbon units, linking threonine catabolism to folate-mediated metabolism and mitochondrial one-carbon pathways.
• Thermostability and catalytic activity of L-threonine aldolase can be improved by targeted mutations in the V-shaped subunit interface.
Description
Threonine aldolase activity (GO:0004793) is a molecular function that catalyzes the cleavage of L-threonine into glycine and acetaldehyde. This reaction is a direct route for threonine catabolism and for the generation of glycine, an amino acid required for protein synthesis, glutathione production, and one-carbon metabolism. The enzyme belongs to the pyridoxal 5'-phosphate (PLP)-dependent family of aldolases and has been studied for decades because of its close relationship with serine hydroxymethyltransferase (SHMT). In some organisms, threonine aldolase and SHMT activities have been proposed to be carried out by the same protein, making GO:0004793 an important node for understanding amino acid interconversion. Researchers care about threonine aldolase activity because it connects threonine availability to glycine and one-carbon pools. In Lactococcus lactis IL1403, an excess of threonine compared with serine promotes threonine aldolase activity, showing that substrate balance directly controls flux through this reaction. In mammalian systems, mitochondrial one-carbon metabolism and serine synthesis pathways are increasingly recognized as regulators of glycine homeostasis and redox balance. For example, reversed SHMT2 activity can drive glycine depletion and acetaminophen hepatotoxicity in metabolic dysfunction-associated steatotic liver disease (MASLD). These findings place threonine aldolase activity within a broader metabolic network that influences liver injury, cancer, and mitochondrial function. From a biotechnology perspective, L-threonine aldolase is also a target for protein engineering. Targeted mutations in the V-shaped subunit interface have been shown to improve both thermostability and activity of L-threonine aldolase, demonstrating that the quaternary structure is critical for catalysis. This makes GO:0004793 relevant not only to basic enzymology but also to industrial biocatalysis and metabolic engineering. Understanding its mechanism, regulation, and disease connections requires combining structural biology, metabolic flux analysis, and CRISPR-based genetic models.
threonine aldolase activity At A Glance
| GO ID | GO:0004793 |
|---|---|
| GO term | threonine aldolase activity |
| Ontology | molecular_function |
| Synonym | L-threonine acetaldehyde-lyase activity; L-threonine acetaldehyde-lyase (glycine-forming); L-threonine aldolase activity |
| Definition | Catalysis of the reaction: L-threonine = glycine + acetaldehyde |
| Major function | Cleavage of L-threonine to glycine and acetaldehyde |
| Cofactor | Pyridoxal 5'-phosphate (PLP) |
| Related enzyme | Serine hydroxymethyltransferase (SHMT) |
| Substrate | L-threonine |
| Products | Glycine and acetaldehyde |
What Is GO:0004793?
GO:0004793 threonine aldolase activity is the catalysis of the reaction L-threonine = glycine + acetaldehyde. In other words, it is the enzyme activity that breaks the carbon-carbon bond of L-threonine to release glycine and acetaldehyde. The reaction is reversible in principle and is dependent on pyridoxal 5'-phosphate (PLP) as a cofactor. The term is classified as a molecular_function in the Gene Ontology and includes synonyms such as L-threonine acetaldehyde-lyase activity, L-threonine acetaldehyde-lyase (glycine-forming), and L-threonine aldolase activity.
Why Is threonine aldolase activity Important in Cell Biology?
Threonine aldolase activity is important because it provides an alternative route for glycine synthesis and threonine catabolism, linking amino acid metabolism to one-carbon folate pools and redox homeostasis. In bacteria such as Lactococcus lactis, the balance between threonine and serine directly controls threonine aldolase activity, which affects glycine availability and growth. In mammalian cells, mitochondrial one-carbon metabolism and serine synthesis pathways are critical for glycine homeostasis, and their dysregulation contributes to liver toxicity and cancer. The enzyme is also a target for protein engineering, where mutations in the V-shaped subunit interface can enhance thermostability and catalytic activity. Thus, GO:0004793 sits at the intersection of basic enzymology, metabolic disease, and biotechnology.
• Provides a direct route from L-threonine to glycine, supporting protein synthesis and glutathione production.
• Links threonine catabolism to one-carbon metabolism and folate-dependent processes.
• Is closely related to serine hydroxymethyltransferase (SHMT), with possible identity in some organisms.
• Substrate balance (threonine vs serine) regulates threonine aldolase activity in Lactococcus lactis.
• Reversed SHMT2 activity can drive glycine depletion and acetaminophen hepatotoxicity in MASLD.
• Phosphorylated SHMT2 regulates oncogenesis through m6A modification in lung adenocarcinoma.
• Mitochondrial one-carbon pathway is rewired in undifferentiated thyroid cancer.
• Succinate accumulation suppresses de novo purine synthesis via succinylation of the mitochondrial folate cycle.
• Mitochondrial translation requires folate-dependent tRNA methylation, connecting one-carbon metabolism to gene expression.
• Engineered L-threonine aldolase variants with improved thermostability and activity are valuable for biocatalysis.
Molecular Mechanism of threonine aldolase activity
Substrate binding and PLP cofactor
In simple terms: The enzyme uses a helper molecule called PLP to grab L-threonine and break it apart.
Threonine aldolase activity requires pyridoxal 5'-phosphate (PLP) as a cofactor, which forms a Schiff base with the amino group of L-threonine. This covalent intermediate activates the substrate for cleavage. The enzyme is classified as a PLP-dependent aldolase, and its mechanism is closely related to that of serine hydroxymethyltransferase (SHMT). In some organisms, threonine aldolase and SHMT activities may be carried out by the same protein, suggesting a shared catalytic strategy.
Catalytic cleavage of L-threonine
In simple terms: The enzyme cuts L-threonine into two pieces: glycine and acetaldehyde.
The catalytic reaction converts L-threonine into glycine and acetaldehyde. This retro-aldol cleavage breaks the C3-C4 bond of threonine, releasing acetaldehyde and leaving glycine bound to PLP. The reaction is reversible, and the equilibrium can favor either direction depending on substrate and product concentrations. In Lactococcus lactis IL1403, excess threonine compared with serine promotes threonine aldolase activity, indicating that substrate availability drives flux through this reaction.
Structural determinants and subunit interface
In simple terms: The shape of the enzyme, especially where subunits meet, controls how well it works.
L-threonine aldolase functions as a multimeric enzyme, and the V-shaped subunit interface is critical for its stability and activity. Targeted mutations in this interface have been shown to improve both thermostability and catalytic activity, demonstrating that quaternary structure modulates the active site. These findings highlight that the enzyme's oligomeric state is not merely structural but directly influences catalysis.
Relationship to serine hydroxymethyltransferase
In simple terms: Threonine aldolase and SHMT are like cousins, and sometimes they might be the same protein.
Serine hydroxymethyltransferase (SHMT) and threonine aldolase share mechanistic and structural similarities, and the question of whether they are identical has been debated. SHMT primarily catalyzes the conversion of serine and tetrahydrofolate to glycine and 5,10-methylenetetrahydrofolate, but it can also exhibit threonine aldolase activity under certain conditions. In mammalian mitochondria, SHMT2 is a key enzyme in one-carbon metabolism, and its reversed activity can drive glycine depletion. Phosphorylated SHMT2 regulates oncogenesis through m6A modification in lung adenocarcinoma, linking this enzyme family to cancer biology.
Regulation by substrate balance and metabolic context
In simple terms: What the cell eats and how much of each amino acid is around can turn this enzyme up or down.
Threonine aldolase activity is regulated by the relative abundance of threonine and serine. In Lactococcus lactis IL1403, an excess of threonine compared with serine promotes threonine aldolase activity, suggesting substrate-level control. In mammalian systems, mitochondrial one-carbon metabolism and serine synthesis pathways influence glycine homeostasis, and their dysregulation can lead to disease. For example, reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in MASLD. Succinate accumulation can also suppress de novo purine synthesis through succinylation-mediated control of the mitochondrial folate cycle, indirectly affecting one-carbon flux.
Key Genes Involved in GO:0004793 threonine aldolase activity
The following genes and proteins are directly or functionally linked to threonine aldolase activity (GO:0004793) and its metabolic network.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SHMT1 | Serine hydroxymethyltransferase 1, cytosolic | Related enzyme with overlapping threonine aldolase activity |
| SHMT2 | Serine hydroxymethyltransferase 2, mitochondrial | Reversed activity drives glycine depletion in MASLD; phosphorylated form regulates oncogenesis |
| GLDC | Glycine decarboxylase | Glycine cleavage system, linked to one-carbon metabolism |
| MTHFD2 | Methylenetetrahydrofolate dehydrogenase 2 | Mitochondrial one-carbon pathway, rewired in thyroid cancer |
| MTHFD1L | Methylenetetrahydrofolate dehydrogenase 1-like | Mitochondrial folate cycle, affected by succinylation |
| MTR | Methionine synthase | Folate-dependent tRNA methylation and translation |
| MTHFD1 | Methylenetetrahydrofolate dehydrogenase 1 | One-carbon metabolism, related to glycine synthesis |
| GCSH | Glycine cleavage system H protein | Glycine homeostasis, linked to threonine aldolase products |
| AMT | Aminomethyltransferase | Glycine cleavage system, one-carbon metabolism |
| DLD | Dihydrolipoamide dehydrogenase | Glycine cleavage system, redox regulation |
| PSAT1 | Phosphoserine aminotransferase 1 | Serine synthesis pathway, affects threonine/serine balance |
| PSPH | Phosphoserine phosphatase | Serine synthesis, related to one-carbon flux |
| PHGDH | Phosphoglycerate dehydrogenase | Serine synthesis, links to glycine and one-carbon metabolism |
| SLC1A4 | Threonine transporter | Threonine uptake, affects substrate availability |
| SLC7A5 | L-type amino acid transporter | Threonine transport, metabolic context |
| GCAT | Glycine C-acetyltransferase | Threonine catabolism alternative route |
| TDH | Threonine dehydrogenase | Threonine catabolism, competing pathway |
How Is threonine aldolase activity Regulated?
Threonine aldolase activity is regulated at multiple levels. At the substrate level, the ratio of threonine to serine controls flux through the enzyme, as shown in Lactococcus lactis IL1403 where excess threonine promotes activity. In mammalian cells, mitochondrial one-carbon metabolism and serine synthesis pathways influence glycine homeostasis, and their dysregulation can alter threonine aldolase-related flux. Phosphorylation of SHMT2 regulates its oncogenic functions through m6A modification in lung adenocarcinoma, suggesting post-translational control of related enzymes. Succinate accumulation can suppress de novo purine synthesis through succinylation-mediated control of the mitochondrial folate cycle, indirectly affecting one-carbon flux and glycine availability. Additionally, mitochondrial translation requires folate-dependent tRNA methylation, linking one-carbon metabolism to gene expression.
threonine aldolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SHMT2 | MASLD, acetaminophen hepatotoxicity | Shmt2 knockout or point-mutation hepatocytes |
| SHMT2 | Lung adenocarcinoma | Phosphorylation-site knock-in or knockout in lung cancer cells |
| MTHFD2 | Undifferentiated thyroid cancer | Mthfd2 knockout in thyroid cancer cell lines |
| MTHFD1L | Succinate-driven purine synthesis suppression | Mthfd1l knockout or succinylation-site mutant |
| MTR | Mitochondrial translation defects | Mtr knockout or knockdown in mitochondrial models |
Threonine aldolase activity and liver disease
Serine synthesis via reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in metabolic dysfunction-associated steatotic liver disease (MASLD). Because threonine aldolase activity also produces glycine, its dysregulation may contribute to glycine depletion in liver disease. This suggests that modulating threonine aldolase or related one-carbon enzymes could be a therapeutic strategy for protecting against hepatotoxicity.
Threonine aldolase activity and cancer
Phosphorylated SHMT2 regulates oncogenesis through m6A modification in lung adenocarcinoma, linking one-carbon metabolism to cancer progression. The mitochondrial one-carbon pathway is rewired in undifferentiated thyroid cancer, indicating that enzymes related to threonine aldolase activity may support tumor growth. Succinate accumulation suppresses de novo purine synthesis through succinylation-mediated control of the mitochondrial folate cycle, further connecting one-carbon metabolism to cancer cell proliferation.
Threonine aldolase activity and mitochondrial function
Mitochondrial translation requires folate-dependent tRNA methylation, tying one-carbon metabolism to mitochondrial gene expression. Threonine aldolase activity supplies glycine, which is essential for mitochondrial protein synthesis and redox balance. Disruption of this pathway can impair mitochondrial function and contribute to metabolic disease.
From threonine aldolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of threonine aldolase activity alter glycine levels? | CRISPR knockout of SHMT1/SHMT2 in cell lines |
| Does a specific point mutation in the V-shaped subunit affect thermostability? | Point-mutation knock-in of L-threonine aldolase |
| Can overexpression of threonine aldolase rescue glycine depletion? | Overexpression cell model |
| How does threonine/serine balance regulate enzyme activity? | Substrate-controlled bacterial or mammalian cell culture |
| Does phosphorylation of SHMT2 affect oncogenesis? | Phospho-mimetic or phospho-dead knock-in |
| Does succinylation of MTHFD1L affect purine synthesis? | Succinylation-site mutant knock-in |
How to Study the threonine aldolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | Glycine and acetaldehyde production | Characterization of wild-type and mutant threonine aldolase |
| Stable isotope tracing | Metabolic flux through one-carbon pathways | Quantifying threonine aldolase contribution to glycine pools |
| X-ray crystallography | Three-dimensional structure | Understanding subunit interface and active site |
| Thermostability assay | Protein stability | Evaluating engineered variants |
| RNA-seq | Gene expression changes | Identifying pathway rewiring in cancer |
| Proteomics | Protein abundance and modifications | Detecting phosphorylation or succinylation |
| Metabolomics | Small molecule levels | Measuring glycine, serine, and one-carbon metabolites |
| CRISPR screening | Gene essentiality and function | Identifying regulators of threonine aldolase activity |
Enzymatic activity assays
Threonine aldolase activity can be measured by monitoring the formation of glycine and acetaldehyde from L-threonine using colorimetric or chromatographic methods. These assays are essential for characterizing wild-type and mutant enzymes, such as those with targeted mutations in the V-shaped subunit interface. Substrate balance experiments, such as varying threonine and serine concentrations, can reveal regulatory effects.
Metabolic flux analysis
Stable isotope tracing with 13C-labeled threonine or serine can quantify flux through threonine aldolase and related one-carbon pathways. This approach has been used to show that reversed SHMT2 activity drives glycine depletion in MASLD. Combining flux analysis with CRISPR knockout models allows causal testing of specific enzymes.
Structural and biophysical characterization
X-ray crystallography and cryo-electron microscopy can resolve the structure of L-threonine aldolase and its subunit interface. Thermostability assays, such as circular dichroism and differential scanning fluorimetry, can evaluate the impact of targeted mutations. These methods help explain how structural changes affect catalytic activity.
Omics and bioinformatics
Transcriptomics, proteomics, and metabolomics can identify changes in threonine aldolase activity-related pathways in disease models. Multi-omics analyses have revealed rewiring of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer. Bioinformatics integration of these datasets can nominate candidate genes for CRISPR validation.
How CRISPR Can Be Used to Study GO:0004793 threonine aldolase activity
Knockout
CRISPR knockout of SHMT1, SHMT2, or other one-carbon enzymes can test their contribution to threonine aldolase activity and glycine homeostasis. Knockout models have been used to show that reversed SHMT2 activity drives glycine depletion in MASLD. These models are essential for establishing causality between enzyme activity and disease phenotypes.
Point Mutation
Point mutations in the V-shaped subunit interface of L-threonine aldolase can improve thermostability and activity. CRISPR point-mutation knock-in can introduce these specific mutations into the endogenous locus to study their effects on catalysis and stability. Phospho-mimetic or phospho-dead mutations in SHMT2 can test the role of phosphorylation in oncogenesis.
Knock-in
Knock-in of tagged or mutant versions of threonine aldolase or related enzymes allows tracking of protein localization and interactions. For example, a fluorescent tag can be inserted to monitor enzyme dynamics in live cells. Knock-in of disease-associated mutations can model human metabolic disorders.
Overexpression
Overexpression of threonine aldolase or SHMT2 can rescue glycine depletion or drive metabolic rewiring in cancer models. Overexpression cell models are useful for testing whether increased enzyme activity is sufficient to alter disease phenotypes. These models can also be used to screen for inhibitors or activators of the enzyme.
How EDITGENE Supports threonine aldolase activity Research
Researchers studying threonine aldolase activity-related genes often need to determine whether a candidate gene is causally involved in a metabolic or disease phenotype. EDITGENE provides CRISPR-based cell model services that enable precise genetic manipulation of these genes, from knockout to point mutation, knock-in, and overexpression. By combining these models with metabolic and omics readouts, researchers can rigorously test hypotheses about GO:0004793 and its role in health and disease.
Contact EDITGENE today to design your custom CRISPR model for threonine aldolase activity research.
Frequently Asked Questions About threonine aldolase activity
What is threonine aldolase activity?
Threonine aldolase activity (GO:0004793) is the catalysis of the reaction L-threonine = glycine + acetaldehyde, a PLP-dependent cleavage of threonine.
What genes are involved in threonine aldolase activity?
Genes include SHMT1, SHMT2, and related one-carbon metabolism genes such as MTHFD2 and MTHFD1L, which functionally interact with this activity.
What is the GO ID for threonine aldolase activity?
The Gene Ontology ID for threonine aldolase activity is GO:0004793.
Is threonine aldolase the same as serine hydroxymethyltransferase?
They are closely related and may be identical in some organisms, but the question remains debated in the literature.
How is threonine aldolase activity regulated?
It is regulated by substrate balance, such as excess threonine compared with serine, and by post-translational modifications of related enzymes.
What diseases are linked to threonine aldolase activity?
It is linked to MASLD, acetaminophen hepatotoxicity, lung adenocarcinoma, and thyroid cancer through one-carbon metabolism.
How can I study threonine aldolase activity in the lab?
You can use enzymatic assays, stable isotope tracing, CRISPR knockout models, and omics methods.
What cofactor does threonine aldolase require?
Threonine aldolase requires pyridoxal 5'-phosphate (PLP) as a cofactor.
Can threonine aldolase activity be engineered for better thermostability?
Yes, targeted mutations in the V-shaped subunit interface can improve thermostability and activity.
What CRISPR models are available for threonine aldolase research?
EDITGENE provides knockout, point-mutation, knock-in, and overexpression cell models for genes related to GO:0004793.
Conclusion
Threonine aldolase activity (GO:0004793) is a fundamental molecular function that cleaves L-threonine into glycine and acetaldehyde, linking amino acid catabolism to one-carbon metabolism and glycine homeostasis. Its close relationship with serine hydroxymethyltransferase and its role in metabolic diseases such as MASLD and cancer make it a compelling target for research. Advances in protein engineering and CRISPR-based models are enabling precise interrogation of this enzyme's mechanism and regulation. By combining enzymatic assays, metabolic flux analysis, and genome editing, researchers can uncover new therapeutic opportunities targeting threonine aldolase activity.
References
- 1. Fang S et al.. 2024. Thermostability and activity improvement in l-threonine aldolase through targeted mutations in V-shaped subunit.. Int J Biol Macromol 278(Pt 4):134994 PMID: 39181367
- 2. Ghrayeb A et al.. 2024. Serine synthesis via reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in MASLD.. Cell Metab 36(1):116-129.e7 PMID: 38171331
- 3. Han T et al.. 2024. Phosphorylated SHMT2 Regulates Oncogenesis Through m(6)A Modification in Lung Adenocarcinoma.. Adv Sci (Weinh) 11(18):e2307834 PMID: 38460155
- 4. Lee SE et al.. 2024. Unraveling the role of the mitochondrial one-carbon pathway in undifferentiated thyroid cancer by multi-omics analyses.. Nat Commun 15(1):1163 PMID: 38331894
- 5. Nengroo MA et al.. 2025. Accumulation of succinate suppresses de novo purine synthesis through succinylation-mediated control of the mitochondrial folate cycle.. Mol Cell 85(22):4215-4228.e9 PMID: 41161310
- 6. Aller K et al.. 2015. Excess of threonine compared with serine promotes threonine aldolase activity in Lactococcus lactis IL1403.. Microbiology (Reading) 161(Pt 5):1073-1080 PMID: 25743155
- 7. Morscher RJ et al.. 2018. Mitochondrial translation requires folate-dependent tRNA methylation.. Nature 554(7690):128-132 PMID: 29364879
- 8. Ogawa H et al.. 2000. Serine hydroxymethyltransferase and threonine aldolase: are they identical?. Int J Biochem Cell Biol 32(3):289-301 PMID: 10716626
