GO:0004766 spermidine synthase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004766 spermidine synthase activity catalyzes the transfer of an aminopropyl group from decarboxylated S-adenosylmethionine to putrescine, producing spermidine and 5'-methylthioadenosine.
• Spermidine is a polyamine essential for cell growth, translation, autophagy, and mitochondrial function, and its synthesis is tightly linked to the hypusination of EIF5A.
• Spermidine synthase activity influences diverse processes including DNA sensing, inflammation resolution, and cancer progression.
• Dysregulated spermidine synthase activity is implicated in cancers such as neuroblastoma and prostate cancer, and in metabolic diseases like non-alcoholic steatohepatitis.
• CRISPR knockout, point mutation, knock-in, and overexpression models enable precise dissection of spermidine synthase function in health and disease.
• Key research methods include metabolomics, enzyme assays, ribosome profiling, and CRISPR library screening to identify genetic dependencies.
Description
Spermidine synthase activity (GO:0004766) is a molecular function that catalyzes the formation of spermidine, a polyamine critical for cellular proliferation, differentiation, and survival. This enzymatic activity is conserved across eukaryotes and prokaryotes and represents a key node in polyamine metabolism, linking methionine salvage to the hypusination of eukaryotic translation initiation factor 5A (EIF5A). Because spermidine levels influence translation, autophagy, mitochondrial respiration, and immune cell function, understanding the regulation and impact of spermidine synthase activity is of broad biomedical importance. Recent studies have revealed that spermidine synthase activity is not merely a housekeeping function; it modulates B-to-Z DNA transitions to control the DNA sensor cGAS, thereby impacting innate immunity. In cancer, secreted spermidine synthase can act in a paracrine manner to suppress prostate cancer growth, highlighting non-canonical roles. Moreover, pharmacological targeting of polyamine synthesis, such as with eflornithine, shows promise in high-risk neuroblastoma. These findings underscore the need for precise genetic tools to study spermidine synthase activity in relevant physiological contexts. This article provides a research-grade overview of GO:0004766, covering its definition, mechanism, key genes, disease associations, and state-of-the-art methods including CRISPR-based models. All statements are grounded in peer-reviewed literature to support researchers in designing robust experiments.
spermidine synthase activity At A Glance
| GO ID | GO:0004766 |
|---|---|
| GO term | spermidine synthase activity |
| Ontology | molecular_function |
| Synonym | aminopropyltransferase activity; putrescine aminopropyltransferase activity; S-adenosylmethioninamine:putrescine 3-aminopropyltransferase activity; SpeE; spermidine synthetase activity |
| Major function | Catalyzes the synthesis of spermidine from putrescine and decarboxylated S-adenosylmethionine |
| Reaction | S-adenosylmethioninamine + putrescine = 5'-methylthioadenosine + spermidine |
| Substrates | Putrescine and decarboxylated S-adenosylmethionine |
| Products | Spermidine and 5'-methylthioadenosine |
| Cofactors | None known; pyridoxal phosphate-independent |
What Is GO:0004766?
According to the Gene Ontology, spermidine synthase activity (GO:0004766) is defined as the catalysis of the reaction: S-adenosylmethioninamine + putrescine = 5'-methylthioadenosine + spermidine. In other words, it is the enzyme activity that transfers an aminopropyl group from decarboxylated S-adenosylmethionine (also known as S-adenosylmethioninamine) to putrescine, yielding spermidine and 5'-methylthioadenosine. This activity is synonymous with aminopropyltransferase, putrescine aminopropyltransferase, and spermidine synthetase, and is often referred to as SpeE in bacteria.
Why Is spermidine synthase activity Important in Cell Biology?
Spermidine synthase activity is essential for polyamine homeostasis, which in turn regulates fundamental cellular processes such as translation, autophagy, and mitochondrial metabolism. Spermidine serves as a substrate for hypusination of EIF5A, a modification required for the translation of proteins involved in mitochondrial fatty acid oxidation and inflammation resolution. Consequently, perturbations in spermidine synthase activity have been linked to metabolic disorders, cancer, and immune dysregulation. Understanding this activity provides insights into disease mechanisms and potential therapeutic targets.
• Spermidine is required for EIF5A hypusination, which supports mitochondrial respiration and macrophage activation.
• Spermidine-mediated hypusination of EIF5A prevents non-alcoholic steatohepatitis progression by improving mitochondrial fatty acid oxidation.
• Polyamine metabolism, including spermidine synthase activity, controls B-to-Z DNA transition and cGAS-dependent DNA sensing.
• Spermidine restricts neonatal inflammation by shaping polymorphonuclear myeloid-derived suppressor cells.
• Secreted spermidine synthase has a paracrine role in suppressing prostate cancer growth downstream of PGC1α.
• Inhibition of polyamine synthesis with eflornithine is a therapeutic strategy for high-risk neuroblastoma.
• Spermidine synthase is a target for producing spermidine in biotechnological applications.
• Dysregulated polyamine metabolism is associated with cancer, neurodegeneration, and aging.
• Spermidine synthase activity is conserved from bacteria to humans, facilitating model organism studies.
• Genetic manipulation of spermidine synthase enables dissection of its cell-autonomous and non-cell-autonomous roles.
Molecular Mechanism of spermidine synthase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs two molecules and joins them together, releasing a byproduct.
Spermidine synthase binds its substrates, putrescine and decarboxylated S-adenosylmethionine (dcAdoMet), in an ordered manner. The enzyme transfers the aminopropyl group from dcAdoMet to putrescine, forming spermidine and releasing 5'-methylthioadenosine (MTA). This reaction is part of the polyamine biosynthetic pathway and is highly conserved across species.
Cofactors and Metal Requirements
In simple terms: No special helper molecules are needed for this reaction.
Spermidine synthase activity does not require pyridoxal phosphate or metal cofactors; it is a simple aminopropyltransferase. The reaction proceeds via a ping-pong or sequential mechanism depending on the organism, but detailed kinetic studies are limited. The enzyme's activity is primarily regulated by substrate availability and product inhibition.
Role in Polyamine Homeostasis
In simple terms: This enzyme helps keep the right balance of polyamines in the cell.
Spermidine synthase contributes to the pool of spermidine, which is further converted to spermine by spermine synthase. Polyamine levels are tightly regulated through biosynthesis, catabolism, and transport. Spermidine synthase activity is coordinated with ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AMD1) to maintain polyamine homeostasis.
Post-translational Regulation and Interacting Proteins
In simple terms: The enzyme can be controlled by modifications or by binding to other proteins.
While specific post-translational modifications of spermidine synthase are not extensively characterized, its activity can be influenced by the availability of dcAdoMet, which is produced by AMD1. In prostate cancer, secreted spermidine synthase acts in a paracrine manner, suggesting extracellular roles. Additionally, polyamine metabolism intersects with the hypusination pathway, where spermidine serves as a substrate for EIF5A modification.
Genetic Regulation and Feedback
In simple terms: The cell can adjust how much of this enzyme is made based on need.
Expression of spermidine synthase is regulated at the transcriptional level in response to growth signals and polyamine levels. Antizyme, a negative regulator of ODC, also affects polyamine pools. However, direct feedback on spermidine synthase is less understood. In cancer, PGC1α induces spermidine synthase secretion, indicating metabolic rewiring.
Key Genes Involved in GO:0004766 spermidine synthase activity
The following genes and proteins are directly or indirectly involved in spermidine synthase activity and its downstream effects.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SRM | Encodes spermidine synthase, the enzyme catalyzing spermidine synthesis | Core enzyme for GO:0004766; target for knockout and overexpression studies |
| AMD1 | Produces decarboxylated S-adenosylmethionine, the aminopropyl donor | Regulates substrate supply for spermidine synthase |
| ODC1 | Ornithine decarboxylase, produces putrescine | Provides substrate for spermidine synthase |
| SMS | Spermine synthase, converts spermidine to spermine | Downstream enzyme in polyamine pathway |
| SAT1 | Spermidine/spermine N1-acetyltransferase, catabolizes polyamines | Regulates polyamine recycling |
| EIF5A | Translation factor activated by spermidine-derived hypusination | Mediates downstream effects of spermidine on translation |
| DHPS | Deoxyhypusine synthase, catalyzes first step of EIF5A hypusination | Links spermidine to translation |
| DOHH | Deoxyhypusine hydroxylase, completes EIF5A hypusination | Required for EIF5A function |
| cGAS | DNA sensor regulated by polyamine metabolism | Connects spermidine to innate immunity |
| PGC1α | Transcriptional coactivator that induces spermidine synthase secretion | Implicated in prostate cancer growth suppression |
| MTAP | Methylthioadenosine phosphorylase, recycles MTA byproduct | Links spermidine synthesis to methionine salvage |
| PAOX | Peroxisomal polyamine oxidase | Catabolizes polyamines |
| SMOX | Spermine oxidase | Catabolizes spermine to spermidine |
| AZIN1 | Antizyme inhibitor, regulates ODC stability | Modulates polyamine synthesis |
| OAZ1 | Antizyme, inhibits ODC and polyamine uptake | Feedback regulator of polyamine levels |
| ATP13A2 | Polyamine transporter | Affects intracellular spermidine levels |
| TP53 | Tumor suppressor, linked to polyamine metabolism | Context-dependent regulation |
| MYC | Oncogene, drives polyamine biosynthesis | Frequently dysregulated in cancer |
How Is spermidine synthase activity Regulated?
Spermidine synthase activity is primarily regulated by substrate availability, particularly the levels of decarboxylated S-adenosylmethionine produced by AMD1 and putrescine produced by ODC1. Polyamine homeostasis is maintained through feedback mechanisms involving antizyme (OAZ1) and antizyme inhibitor (AZIN1), which control ODC stability and polyamine uptake. Additionally, mTOR signaling promotes polyamine synthesis to support cell growth, while AMPK can inhibit it under energy stress. In cancer, oncogenes such as MYC drive polyamine pathway genes, including SRM, to sustain proliferation. Recent evidence shows that PGC1α induces secretion of spermidine synthase in prostate cancer, suggesting extracellular regulation. Furthermore, spermidine levels influence EIF5A hypusination, which in turn affects translation of specific mRNAs, creating a feedback loop between polyamine metabolism and protein synthesis.
spermidine synthase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SRM | Cancer (neuroblastoma, prostate) | Knockout and overexpression in cancer cell lines; xenograft models |
| AMD1 | Metabolic disorders, cancer | Conditional knockout mice; CRISPR point mutations |
| EIF5A | Non-alcoholic steatohepatitis, inflammation | Hypusination-deficient knock-in mice |
| cGAS | Autoinflammatory diseases, innate immunity | Knockout cells for DNA sensing assays |
| PGC1α | Prostate cancer growth suppression | Paracrine co-culture models with secreted SRM |
Cancer
Dysregulated polyamine metabolism is a hallmark of many cancers. Spermidine synthase activity supports rapid proliferation by providing spermidine for EIF5A hypusination and translation of pro-growth proteins. In neuroblastoma, inhibition of polyamine synthesis with eflornithine is under investigation as a therapeutic strategy. In prostate cancer, secreted spermidine synthase acts as a paracrine tumor suppressor downstream of PGC1α, revealing context-dependent roles. Targeting spermidine synthase may therefore have dual effects depending on tumor type.
Metabolic and Inflammatory Diseases
Spermidine-mediated hypusination of EIF5A improves mitochondrial fatty acid oxidation and prevents non-alcoholic steatohepatitis progression, linking spermidine synthase activity to metabolic health. In neonatal inflammation, spermidine restricts inflammatory responses by shaping polymorphonuclear myeloid-derived suppressor cells. These findings suggest that modulating spermidine synthase activity could be beneficial in inflammatory and metabolic disorders.
Innate Immunity and DNA Sensing
Polyamine metabolism controls B-to-Z DNA transition to orchestrate cGAS activity, thereby influencing innate immune responses. Spermidine synthase activity, by maintaining spermidine levels, may impact the sensing of cytosolic DNA and subsequent interferon production. This connection highlights a broader role for spermidine synthase beyond classical metabolism.
From spermidine synthase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SRM affect cell proliferation? | CRISPR knockout of SRM in cancer cell lines |
| How does a specific point mutation in SRM alter catalytic activity? | CRISPR point mutation knock-in of catalytic residues |
| What is the effect of SRM overexpression on polyamine levels? | Lentiviral overexpression of SRM in primary cells |
| Where is SRM localized in cells? | Tagged knock-in of SRM with fluorescent protein |
| Does secreted SRM affect neighboring cells? | Conditioned medium from SRM-overexpressing cells |
| What genes are synthetic lethal with SRM loss? | Genome-wide CRISPR library screening |
How to Study the spermidine synthase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | Spermidine synthase catalytic activity | Validation of enzyme variants |
| LC-MS metabolomics | Polyamine levels (putrescine, spermidine, spermine) | Assessing metabolic impact of genetic edits |
| Ribo-seq | Translation efficiency and ribosome occupancy | Identifying mRNAs dependent on hypusination |
| CRISPR knockout screening | Gene essentiality and synthetic lethality | Discovering pathways interacting with SRM |
| Western blot | Protein expression of SRM and EIF5A hypusination | Confirming knockout or overexpression |
| Immunofluorescence | Subcellular localization of SRM | Tagged knock-in studies |
| Hypusination assay | Levels of hypusinated EIF5A | Linking spermidine to translation |
Enzymatic Activity Assays
Spermidine synthase activity can be measured using radiometric or fluorometric assays that detect the formation of spermidine or 5'-methylthioadenosine from putrescine and decarboxylated S-adenosylmethionine. These assays are useful for validating CRISPR knockout or point mutation effects on catalytic function.
Metabolomics and Polyamine Profiling
Liquid chromatography-mass spectrometry (LC-MS) allows quantification of polyamines including putrescine, spermidine, and spermine, as well as MTA. This method is essential to assess how genetic perturbations of SRM affect cellular polyamine pools.
Ribosome Profiling and Translation Analysis
Because spermidine is required for EIF5A hypusination, changes in spermidine synthase activity impact translation. Ribosome profiling (Ribo-seq) can reveal specific mRNAs whose translation is affected by altered hypusination.
CRISPR Screening and Functional Genomics
Genome-wide CRISPR knockout screens can identify genes that are synthetic lethal with SRM loss or that modulate sensitivity to polyamine pathway inhibitors. Such screens are powerful for uncovering context-specific dependencies.
How CRISPR Can Be Used to Study GO:0004766 spermidine synthase activity
Knockout
CRISPR knockout of SRM eliminates spermidine synthase activity, leading to reduced spermidine levels and impaired EIF5A hypusination. This model is useful to study the consequences of spermidine depletion on cell proliferation, mitochondrial function, and immune responses. Knockout cells can be rescued with exogenous spermidine to confirm specificity.
Point Mutation
CRISPR point mutation can be used to introduce catalytic-dead mutations in SRM, such as altering key residues in the active site. This allows separation of catalytic activity from potential non-enzymatic functions. Point mutations can also mimic disease-associated variants identified in patients.
Knock-in
Knock-in of tagged SRM (e.g., GFP or HA) enables visualization and immunoprecipitation of the endogenous enzyme. This approach is valuable for studying subcellular localization and identifying interacting proteins under physiological expression levels.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of SRM increases spermidine synthase activity, elevating spermidine levels. This model is useful to study the effects of spermidine excess on processes such as autophagy, DNA sensing, and cancer cell growth.
How EDITGENE Supports spermidine synthase activity Research
Researchers studying spermidine synthase activity-related genes often need to determine whether a candidate gene is causally involved in polyamine metabolism, translation, or disease. EDITGENE provides a comprehensive suite of CRISPR services to enable precise genetic manipulation of SRM and related pathway genes, from knockout to knock-in and library screening.
Contact EDITGENE today to design your custom CRISPR model for spermidine synthase activity research.
Frequently Asked Questions About spermidine synthase activity
What is spermidine synthase activity?
Spermidine synthase activity (GO:0004766) is the enzymatic activity that catalyzes the formation of spermidine from putrescine and decarboxylated S-adenosylmethionine, releasing 5'-methylthioadenosine.
What genes are involved in spermidine synthase activity?
The primary gene is SRM, which encodes spermidine synthase. Other genes such as AMD1 and ODC1 provide substrates, while EIF5A mediates downstream effects.
What is the role of spermidine in the cell?
Spermidine is a polyamine essential for cell growth, translation (via EIF5A hypusination), autophagy, and mitochondrial function.
How is spermidine synthase activity regulated?
It is regulated by substrate availability (dcAdoMet and putrescine), feedback mechanisms involving antizyme, and oncogenic signals such as MYC.
What diseases are associated with spermidine synthase?
Dysregulated spermidine synthase activity is implicated in cancers (neuroblastoma, prostate), metabolic diseases (NASH), and inflammatory conditions.
How can I study spermidine synthase activity in the lab?
Common methods include enzymatic assays, LC-MS metabolomics, Ribo-seq, and CRISPR knockout or overexpression models.
What is the connection between spermidine and EIF5A?
Spermidine is the substrate for hypusination of EIF5A, a modification required for EIF5A function in translation.
Can spermidine synthase be targeted for cancer therapy?
Yes, inhibitors of polyamine synthesis such as eflornithine are being tested in neuroblastoma, and secreted spermidine synthase has paracrine effects in prostate cancer.
What CRISPR models are available for spermidine synthase research?
EDITGENE offers knockout, point mutation, knock-in, overexpression, and library screening services for SRM and related genes.
What is the reaction catalyzed by spermidine synthase?
S-adenosylmethioninamine + putrescine = 5'-methylthioadenosine + spermidine.
Conclusion
Spermidine synthase activity (GO:0004766) is a central enzymatic function in polyamine metabolism with far-reaching implications for translation, mitochondrial function, immunity, and cancer. The integration of CRISPR-based genetic models with metabolomic and translational profiling is essential to unravel its context-specific roles. EDITGENE provides the tools and expertise to facilitate such research, from custom knockout and knock-in cell lines to genome-wide screens.
References
- 1. Zhao C et al.. 2023. Polyamine metabolism controls B-to-Z DNA transition to orchestrate DNA sensor cGAS activity.. Immunity 56(11):2508-2522.e6 PMID: 37848037
- 2. Zhou J et al.. 2022. Spermidine-mediated hypusination of translation factor EIF5A improves mitochondrial fatty acid oxidation and prevents non-alcoholic steatohepatitis progression.. Nat Commun 13(1):5202 PMID: 36057633
- 3. Puleston DJ et al.. 2019. Polyamines and eIF5A Hypusination Modulate Mitochondrial Respiration and Macrophage Activation.. Cell Metab 30(2):352-363.e8 PMID: 31130465
- 4. Chen J et al.. 2025. Spermidine restricts neonatal inflammation via metabolic shaping of polymorphonuclear myeloid-derived suppressor cells.. J Clin Invest 135(7) PMID: 40166929
- 5. Pegg AE et al.. 2010. Spermine synthase.. Cell Mol Life Sci 67(1):113-21 PMID: 19859664
- 6. Jiang J et al.. 2024. Eflornithine for treatment of high-risk neuroblastoma.. Trends Pharmacol Sci 45(6):577-578 PMID: 38749882
- 7. Liu W et al.. 2023. Insights into the Unusual Activity of a Novel Homospermidine Synthase with a Promising Application to Produce Spermidine.. J Agric Food Chem 71(35):13024-13034 PMID: 37622688
- 8. Schaub-Clerigué A et al.. 2025. Secreted spermidine synthase reveals a paracrine role for PGC1α-induced growth suppression in prostate cancer.. Cell Death Dis 16(1):330 PMID: 40268923
