GO:0006544 glycine metabolic process: Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0006544 (glycine metabolic process) describes all chemical reactions and pathways involving glycine, the simplest amino acid.
• Glycine is central to one-carbon metabolism, supporting nucleotide synthesis, methylation, and redox balance.
• In skeletal muscle, glycine metabolism contributes to metabolic homeostasis and influences whole-body glucose and energy balance.
• Glycine turnover and decarboxylation can be quantified in vivo using stable isotope infusions, revealing sex-specific differences in healthy adults.
• Dysregulated glycine metabolism is implicated in cancer, where it supports rapid proliferation and is a target for starvation therapy.
• In anaerobes, glycine is fermented via the glycine reductase pathway, highlighting its ancient and diverse metabolic roles.
Description
Glycine metabolic process (GO:0006544) encompasses the chemical reactions and pathways involving glycine, the simplest amino acid. Glycine is not only a proteinogenic amino acid but also a key metabolite in one-carbon metabolism, glutathione synthesis, and neurotransmission. Its metabolic flux is tightly regulated and intersects with serine, folate, and methionine cycles, making it essential for cell proliferation, redox homeostasis, and epigenetic regulation. In skeletal muscle, glycine metabolism contributes to metabolic homeostasis and whole-body energy balance. Quantifying glycine turnover in humans using stable isotopes has revealed that glycine decarboxylation rates differ between men and women, underscoring the importance of sex-specific metabolic studies. In anaerobic bacteria, glycine is fermented via the glycine reductase pathway, demonstrating the evolutionary conservation of glycine metabolism. Given its broad impact, glycine metabolic process is a focal point for cancer research, metabolic disorders, and neurobiology.
glycine metabolic process At A Glance
| GO ID | GO:0006544 |
|---|---|
| GO term | glycine metabolic process |
| Ontology | biological_process |
| Synonym | glycine metabolism |
| Major function | Chemical reactions and pathways involving glycine, including its synthesis, degradation, and interconversion with serine. |
| Related pathways | One-carbon metabolism, serine-glycine cycle, glutathione synthesis, glycine cleavage system. |
| Tissue distribution | Liver, kidney, skeletal muscle, brain, and rapidly proliferating cancer cells. |
| Key enzymes | SHMT1/2, GLDC, GCSH, AMT, MTHFD1/2, PHGDH, PSAT1, PSPH. |
| Clinical relevance | Cancer, metabolic disorders, and neurological conditions. |
What Is GO:0006544?
According to the Gene Ontology, glycine metabolic process (GO:0006544) is defined as the chemical reactions and pathways involving glycine, aminoethanoic acid. This includes its biosynthesis, degradation, interconversion with serine, and its utilization in various metabolic pathways such as one-carbon metabolism and glutathione synthesis.
Why Is glycine metabolic process Important in Cell Biology?
Glycine metabolic process is fundamental to cellular metabolism because glycine serves as a precursor for proteins, glutathione, heme, creatine, and nucleotides. It is a major source of one-carbon units for methylation reactions and nucleotide synthesis, supporting rapid cell proliferation. In skeletal muscle, glycine metabolism helps maintain metabolic homeostasis and influences insulin sensitivity. Dysregulation of glycine metabolism is observed in cancer, where tumor cells reprogram glycine flux to sustain growth, making it a target for cancer starvation therapy. Additionally, glycine is the primary inhibitory neurotransmitter in the spinal cord and brainstem, linking metabolism to neural function. Understanding glycine metabolic process is therefore critical for developing therapies for cancer, metabolic diseases, and neurological disorders.
• Supports nucleotide biosynthesis and one-carbon metabolism for cell proliferation.
• Maintains redox balance through glutathione synthesis.
• Regulates skeletal muscle metabolic homeostasis and whole-body energy balance.
• Provides a target for cancer starvation therapy due to high demand in tumors.
• Influences neurotransmission as the primary inhibitory neurotransmitter in the spinal cord.
• Shows sex-specific differences in turnover and decarboxylation rates in humans.
• Is conserved in anaerobic bacteria via the glycine reductase pathway.
• Impacts drug metabolism, as seen with aspirin pharmacokinetics and glycine conjugation.
What Happens During glycine metabolic process?
Glycine Biosynthesis from Serine
In simple terms: The body can make glycine from another amino acid called serine.
Glycine is synthesized from serine primarily through the reversible reaction catalyzed by serine hydroxymethyltransferase (SHMT1 in the cytoplasm and SHMT2 in mitochondria). This reaction also produces 5,10-methylenetetrahydrofolate, linking glycine synthesis to one-carbon metabolism. In cancer cells, this pathway is often upregulated to meet the high demand for glycine and one-carbon units.
Glycine Cleavage System
In simple terms: Glycine can be broken down to provide energy and building blocks.
The glycine cleavage system (GCS) is a multienzyme complex composed of P-protein (GLDC), H-protein (GCSH), T-protein (AMT), and L-protein (DLD) that catalyzes the oxidative decarboxylation of glycine to CO2, NH3, and 5,10-methylenetetrahydrofolate. This system is a major source of one-carbon units in mitochondria and is essential for glycine homeostasis. Defects in GCS cause non-ketotic hyperglycinemia, a severe neurological disorder.
Glycine as a One-Carbon Donor
In simple terms: Glycine helps supply chemical tags that are used to build DNA and modify proteins.
Through the glycine cleavage system and SHMT reactions, glycine contributes to the one-carbon pool, which fuels nucleotide synthesis (purines and thymidylate) and methylation reactions (e.g., DNA and histone methylation). This role is critical for rapidly dividing cells, including cancer cells, which often exhibit increased glycine metabolism.
Glycine in Glutathione Synthesis
In simple terms: Glycine is a building block for an antioxidant that protects cells from damage.
Glycine is one of the three amino acids (along with glutamate and cysteine) used to synthesize glutathione, the major intracellular antioxidant. This pathway is vital for maintaining redox balance and protecting cells from oxidative stress, and its dysregulation is linked to cancer and aging.
Glycine Degradation and Fermentation in Anaerobes
In simple terms: Some bacteria break down glycine to survive without oxygen.
In anaerobic bacteria, glycine is fermented via the glycine reductase pathway, producing acetate, ammonia, and ATP. This pathway is a key example of glycine metabolism in energy conservation and has been studied in organisms like Clostridium.
Key Genes Involved in GO:0006544 glycine metabolic process
The following genes encode enzymes and transporters directly involved in glycine metabolic process, as supported by published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SHMT1 | Serine hydroxymethyltransferase 1 (cytoplasmic); interconverts serine and glycine | Target in cancer metabolism; links to one-carbon cycle |
| SHMT2 | Serine hydroxymethyltransferase 2 (mitochondrial); interconverts serine and glycine | Essential for mitochondrial one-carbon metabolism; cancer target |
| GLDC | Glycine decarboxylase; component of glycine cleavage system | Mutations cause non-ketotic hyperglycinemia; altered in cancer |
| GCSH | Glycine cleavage system H protein; carries methylamine group | Defects cause glycine encephalopathy; studied in metabolic disorders |
| AMT | Aminomethyltransferase; component of glycine cleavage system | Mutations cause non-ketotic hyperglycinemia |
| DLD | Dihydrolipoamide dehydrogenase; component of glycine cleavage system | Defects cause E3 deficiency; links to metabolic disorders |
| MTHFD1 | Methylenetetrahydrofolate dehydrogenase 1; one-carbon metabolism | Supports glycine-derived one-carbon flux; cancer relevance |
| MTHFD2 | Methylenetetrahydrofolate dehydrogenase 2; mitochondrial one-carbon metabolism | Upregulated in cancer; target for therapy |
| PHGDH | Phosphoglycerate dehydrogenase; serine biosynthesis | Indirectly affects glycine supply; cancer target |
| PSAT1 | Phosphoserine aminotransferase 1; serine biosynthesis | Links to glycine metabolism; cancer relevance |
| PSPH | Phosphoserine phosphatase; serine biosynthesis | Contributes to glycine supply; studied in cancer |
| SLC6A9 | Glycine transporter 1 (GLYT1); regulates glycine uptake | Important for neurotransmission and metabolic studies |
| SLC6A5 | Glycine transporter 2 (GLYT2); neuronal glycine uptake | Linked to hyperekplexia; glycine synaptic regulation |
| GLRA1 | Glycine receptor alpha 1; mediates inhibitory neurotransmission | Mutations cause hyperekplexia; glycine signaling |
| GLRB | Glycine receptor beta; subunit of glycine receptor | Mutations cause hyperekplexia; glycine signaling |
| GATM | Glycine amidinotransferase; creatine synthesis | Uses glycine for creatine; metabolic studies |
| GAMT | Guanidinoacetate N-methyltransferase; creatine synthesis | Consumes glycine-derived metabolite; metabolic disorders |
| CBS | Cystathionine beta-synthase; transsulfuration | Indirectly links glycine to cysteine and glutathione |
How Is glycine metabolic process Regulated?
Glycine metabolic process is regulated at multiple levels. The glycine cleavage system is allosterically activated by ADP and inhibited by ATP and NADH, reflecting cellular energy status. SHMT1 and SHMT2 expression is regulated by transcription factors such as c-Myc and ATF4 in response to metabolic stress. In cancer, oncogenic signaling (e.g., PI3K/AKT/mTOR) upregulates serine-glycine synthesis enzymes to support proliferation. Additionally, glycine transport across membranes is controlled by SLC6A9 and SLC6A5, which regulate synaptic glycine concentrations. Hormonal and nutritional factors also influence glycine turnover, as shown by sex-specific differences in glycine decarboxylation rates in humans.
glycine metabolic process and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GLDC | Non-ketotic hyperglycinemia; cancer metabolism | Knockout mice, patient-derived iPSCs, cancer cell lines |
| SHMT2 | Cancer proliferation; one-carbon metabolism | Knockout and overexpression in cancer cell lines |
| GLRA1 | Hyperekplexia; glycinergic neurotransmission | Knock-in mouse models, neuronal cell lines |
| SLC6A5 | Hyperekplexia; glycine transporter defect | Knockout mice, electrophysiology |
| GATM | Creatine deficiency syndromes; muscle metabolism | Knockout models, skeletal muscle cells |
Glycine Metabolism in Cancer
Cancer cells exhibit increased glycine metabolism to support rapid proliferation, nucleotide synthesis, and redox balance. Upregulation of SHMT2, MTHFD2, and other one-carbon enzymes is common in tumors, and targeting these enzymes is a promising therapeutic strategy. Cancer starvation therapy aims to exploit metabolic dependencies, including glycine auxotrophy, to selectively kill tumor cells.
Non-Ketotic Hyperglycinemia (Glycine Encephalopathy)
Defects in the glycine cleavage system (GLDC, GCSH, AMT, DLD) cause non-ketotic hyperglycinemia, a severe neurological disorder characterized by elevated glycine levels and neurological impairment. This highlights the critical role of glycine metabolism in brain function.
Glycine Metabolism in Skeletal Muscle and Metabolic Homeostasis
Glycine metabolism in skeletal muscle contributes to whole-body metabolic homeostasis, and altered glycine flux is associated with insulin resistance and metabolic disorders. Stable isotope studies have quantified glycine turnover and decarboxylation in healthy adults, revealing sex-specific differences that may impact metabolic disease risk.
Glycinergic Neurotransmission and Neurological Disorders
Glycine is the primary inhibitory neurotransmitter in the spinal cord and brainstem, and dysfunction of glycinergic synapses is linked to hyperekplexia, epilepsy, and other neurological disorders. Mutations in glycine receptors (GLRA1, GLRB) and transporters (SLC6A5) cause startle disease.
From glycine metabolic process-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of GLDC affect glycine cleavage and one-carbon flux? | GLDC knockout cell lines (e.g., HEK293, HepG2) |
| Does a point mutation in GLRA1 alter glycine receptor function? | Knock-in mice or HEK293 cells expressing mutant GLRA1 |
| Can overexpression of SHMT2 drive cancer cell proliferation? | SHMT2 overexpression in cancer cell lines (e.g., HeLa, MCF7) |
| What is the effect of tagged GCSH on glycine cleavage complex assembly? | Knock-in of FLAG-tagged GCSH in cell lines |
| Does SLC6A9 knockout alter synaptic glycine levels? | SLC6A9 knockout mice or neuronal cultures |
| Can CRISPR library screening identify synthetic lethal partners with glycine metabolism? | Genome-wide CRISPR knockout library in cancer cell lines |
How to Study the glycine metabolic process Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Stable isotope infusion | Glycine turnover and decarboxylation rates in vivo | Human metabolic studies |
| CRISPR knockout screening | Gene essentiality and synthetic lethality | Cancer metabolism target discovery |
| Metabolomics (LC-MS/GC-MS) | Intracellular glycine, serine, and one-carbon metabolites | Pathway flux analysis in cells and tissues |
| 13C-flux analysis | Metabolic flux through serine-glycine cycle | Cancer cell metabolism |
| Patch-clamp electrophysiology | Glycine receptor and transporter function | Neurobiology and hyperekplexia research |
| Western blot and qPCR | Expression of glycine metabolic enzymes | Validation of knockout/overexpression models |
| Enzyme activity assays | Glycine cleavage system and SHMT activity | Functional studies of mutations |
| CRISPR knock-in of tags | Protein localization and interactions | Glycine cleavage complex assembly |
Stable Isotope Tracing
Stable isotope infusions with [1,2-13C2]glycine and [2H3]leucine allow quantification of glycine turnover and decarboxylation rates in vivo, as demonstrated in healthy men and women. This method is gold-standard for measuring glycine metabolic flux in humans.
CRISPR-Cas9 Knockout Screening
Genome-wide CRISPR knockout screens can identify genes essential for glycine metabolism and uncover synthetic lethal interactions, particularly in cancer cells with altered glycine dependency. This approach is powerful for target discovery in one-carbon metabolism.
Metabolomics and Flux Analysis
Mass spectrometry-based metabolomics and 13C-flux analysis measure intracellular glycine, serine, and one-carbon metabolites, revealing pathway activity and rewiring in disease models. These techniques are essential for validating metabolic targets.
Electrophysiology and Imaging
Patch-clamp electrophysiology and fluorescence imaging of glycine transporters and receptors (e.g., GLRA1, SLC6A9) assess glycinergic synaptic function and transport kinetics in neurons. These methods link glycine metabolism to neurotransmission.
How CRISPR Can Be Used to Study GO:0006544 glycine metabolic process
Knockout
CRISPR-Cas9 knockout of genes such as GLDC, SHMT2, or SLC6A9 enables researchers to study loss-of-function phenotypes in glycine metabolism, including altered one-carbon flux, proliferation defects, and neurotransmitter imbalances. Knockout cell lines and mice are valuable for validating metabolic dependencies.
Point Mutation
Introducing precise point mutations (e.g., in GLRA1 or GLDC) using CRISPR base editing or HDR allows modeling of human disease variants, such as hyperekplexia or non-ketotic hyperglycinemia, and assessing their impact on glycine metabolism and signaling.
Knock-in
Knock-in of tagged proteins (e.g., FLAG-GCSH) or reporter genes (e.g., GFP-SHMT2) via CRISPR facilitates live-cell imaging, protein interaction studies, and quantification of glycine metabolic enzymes in their native context.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of genes like SHMT2 or MTHFD2 can model metabolic reprogramming in cancer, driving increased glycine consumption and one-carbon flux, and serving as a platform for drug testing.
How EDITGENE Supports glycine metabolic process Research
Researchers studying glycine metabolic process-related genes often need to determine whether a candidate gene is causally involved in metabolic rewiring, disease progression, or therapeutic response. EDITGENE provides end-to-end CRISPR solutions to generate precisely engineered cell models, enabling functional validation of glycine metabolism targets with high reproducibility.
Contact EDITGENE today to design your custom CRISPR model for glycine metabolic process research.
Frequently Asked Questions About glycine metabolic process
What is glycine metabolic process?
Glycine metabolic process (GO:0006544) encompasses all chemical reactions and pathways involving glycine, including its synthesis from serine, degradation via the glycine cleavage system, and its use in one-carbon metabolism and glutathione synthesis.
What genes are involved in glycine metabolic process?
Key genes include SHMT1, SHMT2, GLDC, GCSH, AMT, DLD, MTHFD1, MTHFD2, PHGDH, PSAT1, PSPH, SLC6A9, SLC6A5, GLRA1, GLRB, GATM, GAMT, and CBS.
How is glycine metabolism regulated?
It is regulated by energy status (ADP/ATP), oncogenic signaling (c-Myc, mTOR), and transcriptional factors like ATF4, as well as by transport proteins that control glycine availability.
Why is glycine metabolism important in cancer?
Cancer cells upregulate glycine metabolism to support rapid proliferation, nucleotide synthesis, and redox balance, making it a target for cancer starvation therapy.
What diseases are linked to glycine metabolic process?
Non-ketotic hyperglycinemia, hyperekplexia, cancer, and metabolic disorders such as insulin resistance are associated with dysregulated glycine metabolism.
How can I measure glycine turnover in humans?
Stable isotope infusions with [1,2-13C2]glycine and [2H3]leucine allow quantification of glycine turnover and decarboxylation rates in vivo.
What is the glycine cleavage system?
The glycine cleavage system is a multienzyme complex (GLDC, GCSH, AMT, DLD) that decarboxylates glycine to produce one-carbon units, ammonia, and CO2.
Can CRISPR be used to study glycine metabolism?
Yes, CRISPR knockout, knock-in, point mutation, and overexpression models enable functional studies of glycine metabolic genes in cell lines and animal models.
What is the role of glycine in neurotransmission?
Glycine is the primary inhibitory neurotransmitter in the spinal cord and brainstem, acting through glycine receptors (GLRA1, GLRB) and transporters (SLC6A9, SLC6A5).
How does glycine metabolism differ between men and women?
Studies using stable isotopes show that glycine turnover and decarboxylation rates differ between healthy men and women, highlighting sex-specific metabolic regulation.
Conclusion
Glycine metabolic process (GO:0006544) is a fundamental biological pathway with far-reaching implications for cell proliferation, redox balance, neurotransmission, and metabolic homeostasis. Its dysregulation is central to cancer, neurological disorders, and metabolic diseases, making it a high-priority target for therapeutic development. Advances in CRISPR-based models and stable isotope tracing continue to unravel the complexities of glycine metabolism, offering new opportunities for precision medicine.
References
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