GO:0004123 cystathionine gamma-lyase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004123 cystathionine gamma-lyase activity describes the catalysis of L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+, a pyridoxal 5'-phosphate-dependent reaction.
• The enzyme CTH (cystathionine gamma-lyase) is the primary human protein annotated with this activity and also accepts D-amino acids as substrates.
• CTH is a major source of hydrogen sulfide and persulfide/polysulfide signaling molecules in vascular, neural and hepatic tissues.
• Loss or dysregulation of CTH activity is linked to endothelial senescence, vascular smooth muscle cell senescence, cognitive impairment and exaggerated liver damage.
• CTH is regulated by phosphorylation, hypoxia, polysulfidation and protein-protein interactions such as binding to p53.
• CRISPR knockout, point-mutation, knock-in and overexpression models are essential to dissect the causal roles of CTH and its regulatory partners in disease.
Description
Cystathionine gamma-lyase activity (GO:0004123) is a molecular function defined by the reaction L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+. This activity is catalyzed by the enzyme cystathionine gamma-lyase (CTH), a pyridoxal 5'-phosphate-dependent enzyme that also accepts D-amino acids as substrates. The reaction is a central step in the transsulfuration pathway, linking methionine metabolism to cysteine biosynthesis and to the production of hydrogen sulfide and reactive sulfur species. Researchers study GO:0004123 because it controls redox balance, vascular tone, neurotransmission and liver homeostasis, and because its dysregulation is implicated in senescence, cognitive decline and tissue injury. The activity is not a static property: it is modulated by phosphorylation, hypoxia, polysulfidation and protein-protein interactions, making it a dynamic node for both mechanistic and translational research.
cystathionine gamma-lyase activity At A Glance
| GO ID | GO:0004123 |
|---|---|
| GO term | cystathionine gamma-lyase activity |
| Ontology | molecular_function |
| Synonym | gamma-cystathionase activity; homoserine deaminase activity; homoserine deaminase-cystathionase activity; homoserine dehydratase activity; L-cystathionine cysteine-lyase (deaminating); L-cystathionine cysteine-lyase (deaminating; 2-oxobutanoate-forming) |
| Major function | Catalysis of L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+ |
| Cofactor | Pyridoxal 5'-phosphate (PLP) |
| Primary human enzyme | CTH (cystathionine gamma-lyase) |
| Substrate range | L-cystathionine and D-amino acids |
| Pathway context | Transsulfuration pathway; hydrogen sulfide and persulfide signaling |
What Is GO:0004123?
In simple terms, GO:0004123 describes the ability of an enzyme to split cystathionine into cysteine, 2-oxobutanoate and ammonium using water. More formally, it is the catalysis of the reaction L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+, as defined by QuickGO. This activity is a molecular function, meaning it describes what a protein does at the biochemical level rather than where it occurs or which pathway it belongs to. The reaction is pyridoxal 5'-phosphate-dependent and is carried out by cystathionine gamma-lyase (CTH), which can also act on D-amino acids and contributes to hydrogen sulfide and persulfide production.
Why Is cystathionine gamma-lyase activity Important in Cell Biology?
GO:0004123 is important because it defines the biochemical step that connects methionine metabolism to cysteine synthesis and to the production of hydrogen sulfide and reactive sulfur species, which are signaling molecules in the vasculature, nervous system and liver. Disruption of this activity has been linked to endothelial senescence, vascular smooth muscle cell senescence, cognitive impairment and exaggerated liver damage, making it a target for mechanistic studies and therapeutic hypotheses. Because the enzyme can be regulated by phosphorylation, hypoxia and polysulfidation, understanding GO:0004123 requires dynamic models rather than static assays.
• Provides cysteine, a building block for glutathione and proteins, through the transsulfuration pathway.
• Generates hydrogen sulfide and persulfide/polysulfide species that act in redox signaling.
• Supports endothelial health; disrupted CTH-p53 binding promotes endothelial senescence.
• Protects against vascular smooth muscle cell senescence and arterial stiffness via Foxm1-Gas1 signaling.
• Contributes to cognitive function through neurotrophin signaling and neurogenesis.
• Limits diethylnitrosamine-induced liver damage in mouse models.
• Is a target of regulation by AMP kinase-dependent phosphorylation under hypoxia.
• Can self-inactivate through polysulfidation during cystine metabolism.
• Is a biomarker and assay target in complex biosamples using activatable fluorogens.
• Offers a druggable node for senescence, neurodegeneration and liver injury research.
Molecular Mechanism of cystathionine gamma-lyase activity
Substrate binding and PLP-dependent catalysis
In simple terms: The enzyme uses a vitamin B6-derived helper to break cystathionine into cysteine and other small molecules.
Cystathionine gamma-lyase (CTH) catalyzes the reaction L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+ using pyridoxal 5'-phosphate as a cofactor. The enzyme can also act on D-amino acids, indicating a broader substrate tolerance than the canonical L-cystathionine reaction. This catalytic step is the defining feature of GO:0004123 and is the basis for assays that profile cystathionine beta/gamma-lyase activity in complex biosamples.
Hydrogen sulfide and persulfide generation
In simple terms: The reaction also produces signaling gases and sulfur-containing molecules that affect cell behavior.
CTH activity contributes to the formation of hydrogen sulfide and persulfide/polysulfide species, which act as redox signaling molecules. Hypoxia increases persulfide and polysulfide formation through AMP kinase-dependent phosphorylation of cystathionine gamma lyase, linking oxygen status to sulfur signaling. CTH can also self-inactivate by polysulfidation during cystine metabolism, providing a feedback mechanism that limits its own activity.
Protein-protein interactions and senescence signaling
In simple terms: The enzyme can bind to other proteins, and when that binding is disrupted, cells can age prematurely.
Disrupted binding of cystathionine gamma-lyase to p53 promotes endothelial senescence, showing that GO:0004123 is not only a catalytic activity but also a node in protein interaction networks. In vascular smooth muscle cells, CTH attenuates senescence via the Foxm1-Gas1 pathway to mediate arterial stiffness. These findings indicate that the cellular consequences of CTH activity depend on its interaction partners and downstream signaling.
Regulation by phosphorylation and oxygen availability
In simple terms: When oxygen is low, chemical tags on the enzyme change how active it is.
Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation. This post-translational modification links metabolic stress to sulfur signaling and suggests that GO:0004123 activity is dynamically tuned by the cellular environment. Such regulation is relevant to ischemia, cancer and inflammatory conditions where oxygen levels fluctuate.
Assays and detection of cystathionine gamma-lyase activity
In simple terms: Special chemical probes can light up when the enzyme is active, making it easier to measure.
Novel activatable fluorogens have been developed to profile cystathionine beta/gamma-lyase activity in complex biosamples, enabling sensitive detection of GO:0004123 in biological mixtures. These tools complement classical biochemical assays and support drug discovery and diagnostic research. Characterization of human CTH enzyme activities toward D-amino acids further expands the substrate scope that assays must consider.
Key Genes Involved in GO:0004123 cystathionine gamma-lyase activity
The following genes and proteins are directly or functionally linked to cystathionine gamma-lyase activity (GO:0004123) based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CTH | Encodes cystathionine gamma-lyase, the primary enzyme for GO:0004123 | Central to transsulfuration, H2S production and disease models |
| TP53 | Tumor suppressor that binds CTH; disrupted binding promotes senescence | Links CTH activity to endothelial senescence |
| FOXM1 | Transcription factor in the Foxm1-Gas1 pathway | Mediates CTH-dependent attenuation of vascular smooth muscle cell senescence |
| GAS1 | Downstream effector in Foxm1-Gas1 signaling | Involved in arterial stiffness regulation |
| AMPK | Kinase that phosphorylates CTH under hypoxia | Regulates persulfide and polysulfide formation |
| CBS | Cystathionine beta-synthase, related transsulfuration enzyme | Often co-profiled with CTH in activity assays |
| MPST | Mercaptopyruvate sulfurtransferase, contributes to H2S production | Part of the sulfur signaling network |
| NFS1 | Iron-sulfur cluster enzyme involved in sulfur metabolism | Context for persulfide generation |
| BDNF | Neurotrophin linked to cognitive function | CTH regulates cognitive function through neurotrophin signaling |
| NGF | Neurotrophin involved in neurogenesis | Implicated in CTH-dependent neurogenesis |
| GCLC | Glutamate-cysteine ligase catalytic subunit | Glutathione synthesis downstream of cysteine supply |
| GCLM | Glutamate-cysteine ligase modifier subunit | Redox balance linked to CTH activity |
| NFE2L2 | NRF2 transcription factor controlling antioxidant genes | Redox response related to CTH function |
| HIF1A | Hypoxia-inducible factor 1 alpha | Hypoxic regulation of CTH phosphorylation |
| IL6 | Inflammatory cytokine | Inflammation context in liver damage models |
| TNF | Tumor necrosis factor | Inflammatory signaling in tissue injury |
| SOD1 | Superoxide dismutase 1 | Oxidative stress context for CTH biology |
| CAT | Catalase | Redox context in senescence studies |
How Is cystathionine gamma-lyase activity Regulated?
Cystathionine gamma-lyase activity (GO:0004123) is regulated at multiple levels. Under hypoxia, AMP kinase-dependent phosphorylation of cystathionine gamma lyase increases persulfide and polysulfide formation, linking oxygen sensing to sulfur signaling. CTH can self-inactivate through polysulfidation during cystine metabolism, providing a feedback brake on its own activity. Protein-protein interactions also regulate its function: disrupted binding of CTH to p53 promotes endothelial senescence, indicating that interaction partners modulate the cellular consequences of the activity. In vascular smooth muscle cells, CTH attenuates senescence via the Foxm1-Gas1 pathway, showing that transcriptional and signaling networks downstream of CTH shape its biological impact. Together, these mechanisms make GO:0004123 a dynamically regulated activity rather than a fixed catalytic property.
cystathionine gamma-lyase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CTH | Endothelial senescence | CTH knockout or point-mutation endothelial cells |
| CTH | Vascular smooth muscle cell senescence and arterial stiffness | CTH knockout mouse or overexpression in VSMCs |
| CTH | Cognitive impairment | CTH knockout mouse with neurobehavioral tests |
| CTH | Liver damage and inflammation | CTH deficiency in diethylnitrosamine-treated mice |
| CTH | Redox imbalance and sulfur signaling | Hypoxia-exposed cells with AMPK phosphorylation mutants |
Vascular senescence and arterial stiffness
Disrupted binding of cystathionine gamma-lyase to p53 promotes endothelial senescence, linking GO:0004123 to vascular aging. In vascular smooth muscle cells, CTH attenuates senescence via the Foxm1-Gas1 pathway to mediate arterial stiffness, suggesting that loss of CTH activity contributes to vascular remodeling. These findings position CTH as a potential target for interventions aimed at preserving vascular health.
Cognitive function and neurogenesis
Cystathionine gamma-lyase is a major regulator of cognitive function through neurotrophin signaling and neurogenesis, indicating that GO:0004123 supports neuronal health. Dysregulation of this activity may contribute to cognitive decline, making it relevant to neurodegenerative research. The link to neurotrophins such as BDNF and NGF provides mechanistic hypotheses for further study.
Liver injury and inflammation
Cystathionine gamma-lyase deficiency exaggerates diethylnitrosamine-induced liver damage in mice, demonstrating a protective role for GO:0004123 in the liver. This model is useful for studying inflammation, oxidative stress and hepatocyte death. The findings suggest that enhancing CTH activity or H2S signaling could be beneficial in liver injury contexts.
Redox imbalance and sulfur signaling
CTH contributes to hydrogen sulfide and persulfide/polysulfide production, which are redox signaling molecules. Self-inactivation by polysulfidation during cystine metabolism shows that the enzyme is sensitive to the redox environment. Hypoxia further increases persulfide and polysulfide formation through AMP kinase-dependent phosphorylation, linking oxygen status to sulfur biology. These mechanisms connect GO:0004123 to oxidative stress-related diseases.
From cystathionine gamma-lyase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of CTH activity cause senescence? | CTH knockout cell lines and mouse models |
| How does phosphorylation regulate CTH under hypoxia? | Point-mutation knock-in of phospho-deficient or phospho-mimetic CTH |
| Can restored CTH activity rescue cognitive defects? | CTH overexpression or knock-in in neurons |
| What is the role of CTH-p53 binding in endothelial cells? | Knock-in of binding-deficient CTH mutants |
| Does CTH protect against liver injury? | CTH knockout mice treated with diethylnitrosamine |
| How does polysulfidation affect CTH self-inactivation? | Point mutations at cysteine residues combined with activity assays |
How to Study the cystathionine gamma-lyase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Activatable fluorogen assay | Cystathionine beta/gamma-lyase activity | Profiling CTH activity in complex biosamples |
| CRISPR knockout | Loss-of-function phenotype | Testing causal role of CTH in senescence and liver injury |
| Point-mutation knock-in | Effect of specific residues on activity or regulation | Phosphorylation and polysulfidation studies |
| Co-immunoprecipitation | Protein-protein interactions | CTH-p53 binding in endothelial cells |
| Senescence staining | Cellular senescence | Endothelial and vascular smooth muscle cell models |
| Neurobehavioral tests | Cognitive function | CTH knockout mice |
| Liver injury markers | Hepatocyte damage | Diethylnitrosamine-treated CTH-deficient mice |
| Sulfur species detection | Persulfide and polysulfide levels | Hypoxia and cystine metabolism studies |
Biochemical activity assays
Cystathionine gamma-lyase activity can be measured using activatable fluorogens that profile cystathionine beta/gamma-lyase in complex biosamples. These assays detect the catalytic step defined by GO:0004123 and are suitable for screening inhibitors or activators. Characterization of human CTH toward D-amino acids expands the substrate panel for such assays.
Genetic knockout and rescue models
CRISPR knockout of CTH in cell lines and mice is used to test the consequences of losing GO:0004123 activity. Rescue experiments with wild-type or mutant CTH can distinguish catalytic activity from protein interaction functions. Such models are essential for linking the activity to senescence, liver damage and cognitive phenotypes.
Phosphorylation and signaling analysis
Hypoxia-induced AMP kinase-dependent phosphorylation of CTH can be studied by phospho-specific antibodies and point-mutation knock-in models. Downstream persulfide and polysulfide formation can be measured with sulfur-sensitive probes. These methods reveal how GO:0004123 is dynamically regulated by oxygen and metabolic stress.
Protein interaction and senescence assays
Co-immunoprecipitation and proximity assays can test CTH-p53 binding and its disruption in senescence models. Senescence markers such as SA-beta-gal and cell cycle inhibitors can be combined with CTH knockout or mutant expression. The Foxm1-Gas1 pathway can be interrogated by transcriptomics and knockdown experiments.
How CRISPR Can Be Used to Study GO:0004123 cystathionine gamma-lyase activity
Knockout
CRISPR knockout of CTH eliminates GO:0004123 activity and is used to test its role in endothelial senescence, vascular smooth muscle cell senescence, cognitive function and liver damage. Knockout models are the first step in establishing causality. They can be combined with rescue constructs to separate catalytic from non-catalytic functions.
Point Mutation
Point-mutation knock-in can alter catalytic residues, phosphorylation sites or polysulfidation sites in CTH to dissect regulation of GO:0004123. For example, phospho-deficient or phospho-mimetic mutants can test the role of AMPK-dependent phosphorylation under hypoxia. Cysteine mutants can probe self-inactivation by polysulfidation.
Knock-in
Knock-in of tagged or mutant CTH allows tracking of protein localization, interaction and activity in vivo. Binding-deficient CTH mutants can test the importance of the CTH-p53 interaction in endothelial senescence. Knock-in models also enable tissue-specific expression studies.
Overexpression
Overexpression of CTH can test whether increasing GO:0004123 activity rescues phenotypes such as cognitive impairment or liver injury. It is also useful for producing sufficient enzyme for biochemical assays and fluorogen profiling. Overexpression models should be interpreted alongside knockout data to avoid artifacts.
How EDITGENE Supports cystathionine gamma-lyase activity Research
Researchers studying cystathionine gamma-lyase activity-related genes often need to determine whether a candidate gene is causally involved in a phenotype or merely correlated with it. This requires precise genetic models that can remove, modify or restore the activity of CTH and its regulatory partners. EDITGENE provides the full spectrum of CRISPR-based tools to build such models efficiently.
Contact EDITGENE today to design your custom CRISPR model for cystathionine gamma-lyase activity research.
Frequently Asked Questions About cystathionine gamma-lyase activity
What is cystathionine gamma-lyase activity?
It is the molecular function defined by GO:0004123, catalyzing L-cystathionine + H2O = 2-oxobutanoate + L-cysteine + NH4+.
What genes are involved in cystathionine gamma-lyase activity?
The primary gene is CTH, which encodes the enzyme; TP53, FOXM1, GAS1 and AMPK are functionally linked regulators.
What is the GO ID for cystathionine gamma-lyase activity?
The GO ID is GO:0004123.
Which enzyme carries out GO:0004123?
Cystathionine gamma-lyase (CTH) is the primary human enzyme, and it can also act on D-amino acids.
How is cystathionine gamma-lyase activity regulated?
It is regulated by phosphorylation, hypoxia, polysulfidation and protein-protein interactions such as binding to p53.
What diseases are linked to cystathionine gamma-lyase activity?
It has been linked to endothelial senescence, vascular smooth muscle cell senescence, cognitive impairment and liver damage.
How can I measure cystathionine gamma-lyase activity?
Activatable fluorogens and biochemical assays can profile the activity in complex biosamples.
What is the role of CTH in the brain?
CTH regulates cognitive function through neurotrophin signaling and neurogenesis.
Does CTH protect the liver?
CTH deficiency exaggerates diethylnitrosamine-induced liver damage in mice, suggesting a protective role.
How can CRISPR help study GO:0004123?
CRISPR knockout, point mutation, knock-in and overexpression models can test the causal role of CTH and its regulators in disease phenotypes.
Conclusion
GO:0004123 cystathionine gamma-lyase activity is a central molecular function that links methionine metabolism to cysteine synthesis, hydrogen sulfide signaling and redox balance. Its dysregulation is implicated in vascular senescence, cognitive impairment and liver injury, making it a high-value target for mechanistic and translational research. Precise CRISPR models are essential to move from correlation to causation, and EDITGENE provides the tools to build them.
References
- 1. Hu J et al.. 2023. Disrupted Binding of Cystathionine γ-Lyase to p53 Promotes Endothelial Senescence.. Circ Res 133(10):842-857 PMID: 37800327
- 2. Araki S et al.. 2023. Cystathionine γ-Lyase Self-Inactivates by Polysulfidation during Cystine Metabolism.. Int J Mol Sci 24(12) PMID: 37373128
- 3. Chakraborty S et al.. 2025. Cystathionine γ-lyase is a major regulator of cognitive function through neurotrophin signaling and neurogenesis.. Proc Natl Acad Sci U S A 122(52):e2528478122 PMID: 41452980
- 4. Miyamoto T et al.. 2022. Characterization of human cystathionine γ-lyase enzyme activities toward d-amino acids.. Biosci Biotechnol Biochem 86(11):1536-1542 PMID: 36085174
- 5. Ligi S et al.. 2024. Cystathionine gamma-lyase deficiency exaggerates diethylnitrosamine-induced liver damage in mice.. Nitric Oxide 151:1-9 PMID: 39151724
- 6. Jia Y et al.. 2022. Profiling Cystathionine β/γ-Lyase in Complex Biosamples Using Novel Activatable Fluorogens.. Anal Chem 94(2):1203-1210 PMID: 34955022
- 7. Alam S et al.. 2023. Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation.. Redox Biol 68:102949 PMID: 37922764
- 8. Lin Q et al.. 2025. Cystathionine γ-Lyase Attenuates Vascular Smooth Muscle Cell Senescence via Foxm1-Gas1 Pathway to Mediate Arterial Stiffness.. Antioxid Redox Signal 42(13-15):655-671 PMID: 39226170
