GO:0008373 sialyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008373 sialyltransferase activity is a molecular function defined as the catalysis of sialic acid transfer to acceptor molecules such as gangliosides or N- and O-linked glycoprotein sugar chains [QuickGO definition].
• Sialyltransferase activity is carried out by a family of enzymes that use CMP-sialic acid as the donor and generate sialylated glycoconjugates.
• Altered sialyltransferase activity is observed in cancer, including elevated serum activity in cancer patients and hypersialylation driven by BRCA1 insufficiency.
• Sialyltransferase activity is dynamically regulated during liver regeneration and in cultured hepatocytes by dexamethasone.
• Platelet glycoprotein sialyltransferase activity is altered in thrombasthenic and Bernard-Soulier platelets.
• Some sialyltransferases, such as ST8Sia5, can autopolysialylate themselves, regulating their own secretion and enzyme activity.
Description
Sialyltransferase activity (GO:0008373) is a molecular function that transfers sialic acid to acceptor molecules, typically the terminal portions of gangliosides or the N- or O-linked sugar chains of glycoproteins [QuickGO definition]. This activity is essential for the biosynthesis of sialylated glycoconjugates, which play critical roles in cell-cell recognition, signaling, and immune regulation. The enzymes responsible, sialyltransferases, are a large family of Golgi-resident type II membrane proteins that utilize CMP-sialic acid as the donor substrate. Researchers study sialyltransferase activity because its dysregulation is linked to multiple human diseases. Elevated serum sialyltransferase activity has been reported in cancer patients, and hypersialylation of the tumor microenvironment promotes metastasis and immunotherapy resistance. Sialyltransferase activity also changes during liver regeneration and in platelet disorders, highlighting its broad physiological importance. Understanding the molecular mechanisms, regulation, and disease relevance of sialyltransferase activity is therefore a key area of biomedical research.
sialyltransferase activity At A Glance
| GO ID | GO:0008373 |
|---|---|
| GO term | sialyltransferase activity |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Catalysis of the transfer of sialic acid to an acceptor molecule, typically gangliosides or N-/O-linked glycoprotein sugar chains [QuickGO definition]. |
| Donor substrate | CMP-sialic acid (CMP-Neu5Ac) |
| Acceptor substrates | Glycolipids (gangliosides), N-linked and O-linked glycoprotein sugar chains [QuickGO definition] |
| Cellular location | Golgi apparatus (implied by sialyltransferase enzyme family) |
| Representative enzymes | ST3GAL, ST6GAL, ST8SIA families [2,3] |
What Is GO:0008373?
According to the Gene Ontology, GO:0008373 sialyltransferase activity is defined as the catalysis of the transfer of sialic acid to an acceptor molecule, typically the terminal portions of the sialylated glycolipids (gangliosides) or to the N- or O-linked sugar chains of glycoproteins [QuickGO definition]. In practice, this means that sialyltransferase enzymes take a sialic acid residue from a donor molecule, usually CMP-sialic acid, and attach it to a sugar chain on a protein or lipid. This reaction is a type of glycosyltransferase activity and is central to the biosynthesis of sialylated glycans.
Why Is sialyltransferase activity Important in Cell Biology?
Sialyltransferase activity is fundamentally important because sialic acid residues on glycoconjugates modulate a vast array of biological processes, including cell adhesion, signal transduction, and immune recognition. Dysregulated sialyltransferase activity is a hallmark of cancer, where it contributes to hypersialylation, metastasis, and resistance to immunotherapy. Serum sialyltransferase activity has been investigated as a biomarker in cancer patients. Beyond cancer, sialyltransferase activity is dynamically regulated during liver regeneration and is altered in platelet disorders such as thrombasthenia and Bernard-Soulier syndrome. Thus, understanding this activity is critical for both basic glycobiology and translational medicine.
• Sialyltransferase activity is essential for the biosynthesis of sialylated glycans, which are involved in cell-cell communication and signaling.
• Elevated serum sialyltransferase activity has been observed in cancer patients, suggesting its potential as a biomarker.
• BRCA1 insufficiency induces a hypersialylated tumor microenvironment that promotes metastasis and immunotherapy resistance, highlighting the role of sialyltransferase activity in cancer progression.
• Sialyltransferase activity is upregulated during liver regeneration, indicating a role in tissue repair.
• Platelet glycoprotein sialyltransferase activity is altered in thrombasthenic and Bernard-Soulier platelets, linking it to bleeding disorders.
• Dexamethasone modulates sialyltransferase activity and secretion in cultured rat hepatocytes, showing hormonal regulation.
• Oncogenic ras transformation can decrease specific sialyltransferase activity, suggesting a link between oncogenes and glycosylation changes.
• Autopolysialylation of ST8Sia5 regulates its own secretion and enzyme activity, revealing a self-regulatory mechanism.
• Sialyltransferase activity is a target for glycoengineering and therapeutic intervention in cancer and immune diseases.
• Studying sialyltransferase activity requires robust methods such as enzyme assays, glycan analysis, and CRISPR-based gene editing.
Molecular Mechanism of sialyltransferase activity
Substrate recognition and donor specificity
In simple terms: Sialyltransferases pick up a sialic acid molecule from a donor and attach it to a sugar chain.
Sialyltransferases utilize CMP-sialic acid (CMP-Neu5Ac) as the donor substrate and transfer sialic acid to acceptor molecules such as galactose, N-acetylgalactosamine, or other sialic acid residues on glycoproteins and glycolipids. The acceptor specificity varies among family members; for example, ST3GAL enzymes add sialic acid in alpha-2,3 linkage, while ST6GAL enzymes add in alpha-2,6 linkage. This specificity determines the structure and function of the resulting sialylated glycans.
Catalytic mechanism
In simple terms: The enzyme catalyzes the transfer of sialic acid via a chemical reaction that forms a new glycosidic bond.
The catalytic mechanism of sialyltransferases involves the nucleophilic attack of a hydroxyl group on the acceptor sugar onto the anomeric carbon of sialic acid in CMP-sialic acid, resulting in the release of CMP and formation of a sialylated product. This reaction is typical of glycosyltransferases and requires divalent metal ions for some family members, although many sialyltransferases are metal-independent. The reaction proceeds with inversion or retention of anomeric configuration depending on the enzyme family.
Autopolysialylation and self-regulation
In simple terms: Some sialyltransferases can add sialic acid to themselves, which affects how they work.
A novel autopolysialylation activity has been described for the ganglioside sialyltransferase ST8Sia5, where the enzyme transfers sialic acid to its own polypeptide chain. This autopolysialylation regulates its secretion and enzyme activity, providing a feedback mechanism. This finding highlights that sialyltransferase activity can be self-modifying, adding a layer of regulation beyond substrate availability.
Regulation by hormones and oncogenes
In simple terms: The activity of sialyltransferases can be turned up or down by hormones and cancer-causing genes.
Dexamethasone, a glucocorticoid, modulates both the activity and secretion of sialyltransferase in primary monolayer cultures of rat hepatocytes. In FR3T3 cells transformed with the ras oncogene, the activity of CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase is decreased, indicating that oncogenic signaling can alter sialyltransferase activity. These examples demonstrate that sialyltransferase activity is subject to hormonal and oncogenic regulation.
Trans-sialidase activity and synthetic applications
In simple terms: Some sialyltransferases can also act in reverse, transferring sialic acid from one sugar to another, which is useful for making sialosides.
The alpha2,6-sialyltransferase from Photobacterium damsela exhibits trans-sialidase activity, meaning it can transfer sialic acid from a donor sialoside to an acceptor without CMP-sialic acid. This trans-sialidase activity has been exploited for the synthesis of sialosides, demonstrating the versatility of sialyltransferase enzymes in biotechnology.
Key Genes Involved in GO:0008373 sialyltransferase activity
The following genes encode enzymes with sialyltransferase activity or are directly involved in its regulation, as supported by the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ST3GAL1 | Alpha-2,3-sialyltransferase; transfers sialic acid to galactose residues | Implicated in cancer and immune regulation |
| ST3GAL2 | Alpha-2,3-sialyltransferase | Potential role in glycan biosynthesis |
| ST3GAL3 | Alpha-2,3-sialyltransferase | Associated with neurological disorders |
| ST3GAL4 | Alpha-2,3-sialyltransferase | Involved in sialyl Lewis X synthesis |
| ST3GAL5 | GM3 synthase; alpha-2,3-sialyltransferase | Mutations cause GM3 synthase deficiency |
| ST3GAL6 | Alpha-2,3-sialyltransferase | Role in cancer metastasis |
| ST6GAL1 | Alpha-2,6-sialyltransferase; adds sialic acid to N-glycans | Key enzyme in hypersialylation and cancer |
| ST6GAL2 | Alpha-2,6-sialyltransferase | Expressed in brain; role in neuronal function |
| ST6GALNAC1 | Alpha-2,6-sialyltransferase for O-glycans | Involved in cancer and immune modulation |
| ST6GALNAC2 | Alpha-2,6-sialyltransferase | Associated with breast cancer |
| ST8SIA1 | GD3 synthase; alpha-2,8-sialyltransferase | Role in ganglioside biosynthesis and cancer |
| ST8SIA2 | Alpha-2,8-sialyltransferase | Involved in polysialic acid synthesis |
| ST8SIA4 | Polysialyltransferase; adds polysialic acid to NCAM | Role in neural development |
| ST8SIA5 | Ganglioside sialyltransferase; autopolysialylation | Regulates its own secretion and activity |
| ST8SIA6 | Alpha-2,8-sialyltransferase | Potential role in immune regulation |
| BRCA1 | DNA repair; loss induces hypersialylation | BRCA1 insufficiency leads to hypersialylated tumor microenvironment |
| RAS | Oncogene; transformation alters sialyltransferase activity | ras transformation decreases specific sialyltransferase activity |
How Is sialyltransferase activity Regulated?
Sialyltransferase activity is regulated at multiple levels. Hormonal regulation is exemplified by dexamethasone, which modulates both the activity and secretion of sialyltransferase in cultured rat hepatocytes. Oncogenic signaling also plays a role: transformation of FR3T3 cells with the ras oncogene leads to decreased activity of a specific alpha-2,3-sialyltransferase. Additionally, BRCA1 insufficiency induces a hypersialylated tumor microenvironment, suggesting that DNA repair pathways can influence sialyltransferase activity. Autopolysialylation of ST8Sia5 represents a self-regulatory mechanism that controls its secretion and enzyme activity. These examples highlight that sialyltransferase activity is dynamically regulated by hormones, oncogenes, and intrinsic feedback loops.
sialyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BRCA1 | Hypersialylated tumor microenvironment, metastasis, immunotherapy resistance | BRCA1 knockout or knockdown cancer cell lines |
| ST6GAL1 | Cancer hypersialylation and metastasis | ST6GAL1 overexpression or knockout in cancer cells |
| ST8SIA5 | Regulation of secretion and enzyme activity via autopolysialylation | ST8SIA5 point mutants or knockout cells |
| RAS | Oncogene-driven changes in sialyltransferase activity | Ras-transformed FR3T3 cells |
| ST3GAL family | Altered sialylation in cancer and neurological disorders | Knockout or knock-in models for specific ST3GAL genes |
Cancer and metastasis
Altered sialyltransferase activity is a hallmark of cancer. Serum sialyltransferase activity is elevated in cancer patients, suggesting its potential as a biomarker. BRCA1 insufficiency induces a hypersialylated acidic tumor microenvironment that promotes metastasis and immunotherapy resistance, directly linking sialyltransferase activity to cancer progression. Additionally, ras oncogene transformation decreases specific sialyltransferase activity in FR3T3 cells, indicating that oncogenic signaling can remodel glycosylation patterns.
Liver regeneration and hepatic function
Sialyltransferase activity is dynamically regulated during liver regeneration, with changes observed in regenerating rat liver. In cultured rat hepatocytes, dexamethasone modulates both the activity and secretion of sialyltransferase, suggesting a role in hepatic stress response and glycoprotein homeostasis. These findings implicate sialyltransferase activity in liver physiology and regeneration.
Platelet disorders
Glycoprotein sialyltransferase activity is altered in platelets from patients with thrombasthenia and Bernard-Soulier syndrome, two inherited bleeding disorders. This suggests that sialyltransferase activity contributes to platelet glycoprotein biology and may be relevant to hemostatic disorders.
From sialyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of a specific sialyltransferase affect glycan profiles? | Knockout cell lines (e.g., ST6GAL1 KO) |
| How does a point mutation in the catalytic domain affect enzyme activity? | Point-mutation knock-in via CRISPR |
| What is the effect of tagging a sialyltransferase on its localization? | Tagged knock-in (e.g., GFP or FLAG) |
| Does overexpression of a sialyltransferase promote metastasis? | Overexpression cell models |
| How does BRCA1 insufficiency alter sialyltransferase activity? | BRCA1 knockout or knockdown cancer cells |
| Can sialyltransferase activity be modulated by dexamethasone? | Primary hepatocyte cultures treated with dexamethasone |
How to Study the sialyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radioactive enzyme assay | Sialyltransferase activity using CMP-[3H]sialic acid | Serum or cell lysate activity measurement |
| Lectin blotting | Sialylation levels and linkage specificity | Detection of hypersialylation in cancer cells |
| Mass spectrometry glycomics | Detailed glycan structures | Profiling sialylated N- and O-glycans |
| CRISPR knockout screening | Genes affecting sialylation | Identifying regulators of sialyltransferase activity |
| Fluorescent tagging and imaging | Subcellular localization and secretion | Studying ST8Sia5 autopolysialylation |
| Trans-sialidase assay | Transfer of sialic acid without CMP-sialic acid | Synthesis of sialosides |
| qPCR and Western blot | Expression levels of sialyltransferases | Correlating expression with activity |
| Flow cytometry with lectins | Cell surface sialylation | Analyzing immune cell sialylation |
Enzymatic assays for sialyltransferase activity
Sialyltransferase activity is typically measured using radioactive or fluorescent donor substrates such as CMP-[3H]sialic acid, followed by separation of products by chromatography [1,4]. These assays can be performed on cell lysates, serum, or purified enzymes. For example, serum sialyltransferase activity in cancer patients was measured using such assays. Trans-sialidase activity can be detected using sialoside donors and acceptors.
Glycan analysis by mass spectrometry and lectin blotting
To determine the products of sialyltransferase activity, researchers use mass spectrometry-based glycomics or lectin blotting with sialic acid-specific lectins. These methods reveal the types and linkages of sialic acids on glycoproteins and glycolipids. Hypersialylation in BRCA1-insufficient cells was detected using such approaches.
CRISPR-based genetic screens
CRISPR knockout screens can identify genes that regulate sialyltransferase activity and sialylation. For instance, knocking out specific sialyltransferases followed by glycan analysis can reveal their contributions to cellular sialylation. Pooled screens with lectin-based selection can uncover modifiers of sialylation.
Imaging and subcellular localization
Fluorescent tagging of sialyltransferases allows visualization of their Golgi localization and trafficking. Autopolysialylation of ST8Sia5 was studied using tagged constructs and secretion assays. Live-cell imaging can track the dynamics of sialyltransferase secretion and activity.
How CRISPR Can Be Used to Study GO:0008373 sialyltransferase activity
Knockout
CRISPR knockout of individual sialyltransferase genes (e.g., ST6GAL1, ST3GAL4) is used to determine their specific contributions to cellular sialylation and downstream phenotypes such as cell migration or immune evasion. Knockout models can also validate whether a candidate gene is required for sialyltransferase activity in a given cell type.
Point Mutation
Point mutations in the catalytic domain of sialyltransferases can be introduced using CRISPR base editing or homology-directed repair to dissect the enzymatic mechanism. For example, mutating the catalytic residues of ST8Sia5 can test their role in autopolysialylation and secretion.
Knock-in
Knock-in of epitope tags (e.g., FLAG, GFP) or reporter genes into endogenous sialyltransferase loci allows real-time tracking of protein localization and secretion without overexpression artifacts. Knock-in of disease-associated mutations can model altered sialyltransferase activity in human cells.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of sialyltransferases is used to study the effects of increased enzyme activity on glycan profiles, cell signaling, and tumorigenesis. Overexpression models can mimic the hypersialylation observed in cancer.
How EDITGENE Supports sialyltransferase activity Research
Researchers studying sialyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in sialylation, disease progression, or therapeutic resistance. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such investigations, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for sialyltransferase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| ST6GALNAC3 Knockout HEK293 Cell Line | EDJ-KQ2432 | Human | 256435 | Details Get a Quote |
| ST6GAL1 Knockout HEK293 Cell Line | EDJ-KQ3167 | Human | 6480 | Details Get a Quote |
| ST3GAL5 Knockout HEK293 Cell Line | EDJ-KQ3838 | Human | 8869 | Details Get a Quote |
| ST3GAL4 Knockout HEK293 Cell Line | EDJ-KQ4997 | Human | 6484 | Details Get a Quote |
| ST3GAL1 Knockout HEK293 Cell Line | EDJ-KQ5748 | Human | 6482 | Details Get a Quote |
| ST8SIA1 Knockout HEK293 Cell Line | EDJ-KQ5749 | Human | 6489 | Details Get a Quote |
| ST3GAL2 Knockout HEK293 Cell Line | EDJ-KQ5751 | Human | 6483 | Details Get a Quote |
| ST8SIA4 Knockout HEK293 Cell Line | EDJ-KQ6142 | Human | 7903 | Details Get a Quote |
| ST8SIA2 Knockout HEK293 Cell Line | EDJ-KQ6176 | Human | 8128 | Details Get a Quote |
| ST3GAL6 Knockout HEK293 Cell Line | EDJ-KQ7036 | Human | 10402 | Details Get a Quote |
| ST6GALNAC2 Knockout HEK293 Cell Line | EDJ-KQ7107 | Human | 10610 | Details Get a Quote |
| ST6GALNAC4 Knockout HEK293 Cell Line | EDJ-KQ8675 | Human | 27090 | Details Get a Quote |
| ST8SIA5 Knockout HEK293 Cell Line | EDJ-KQ9079 | Human | 29906 | Details Get a Quote |
| ST6GALNAC6 Knockout HEK293 Cell Line | EDJ-KQ9179 | Human | 30815 | Details Get a Quote |
| ST6GALNAC5 Knockout HEK293 Cell Line | EDJ-KQ9754 | Human | 81849 | Details Get a Quote |
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Frequently Asked Questions About sialyltransferase activity
What is sialyltransferase activity?
Sialyltransferase activity (GO:0008373) is the catalysis of the transfer of sialic acid to an acceptor molecule, typically gangliosides or N- and O-linked glycoprotein sugar chains [QuickGO definition].
What genes are involved in sialyltransferase activity?
Genes encoding sialyltransferases include ST3GAL1-6, ST6GAL1-2, ST6GALNAC1-6, and ST8SIA1-6, among others [2,3].
What is the GO term for sialyltransferase activity?
The Gene Ontology term is GO:0008373, sialyltransferase activity, under the molecular_function ontology [QuickGO definition].
How is sialyltransferase activity measured?
It is commonly measured using radioactive enzyme assays with CMP-[3H]sialic acid, lectin blotting, or mass spectrometry-based glycomics [1,3].
Is sialyltransferase activity increased in cancer?
Yes, elevated serum sialyltransferase activity has been reported in cancer patients, and hypersialylation is observed in BRCA1-insufficient tumors [1,3].
What is the role of sialyltransferase activity in liver regeneration?
Sialyltransferase activity changes during liver regeneration in rats, suggesting a role in tissue repair.
Can sialyltransferase activity be regulated by hormones?
Yes, dexamethasone modulates sialyltransferase activity and secretion in cultured rat hepatocytes.
What is autopolysialylation in sialyltransferase activity?
Autopolysialylation is a self-modifying activity where a sialyltransferase adds sialic acid to itself, as seen with ST8Sia5, regulating its secretion and activity.
How does ras oncogene affect sialyltransferase activity?
ras transformation of FR3T3 cells decreases a specific alpha-2,3-sialyltransferase activity.
What platelet disorders involve sialyltransferase activity?
Altered glycoprotein sialyltransferase activity has been observed in thrombasthenic and Bernard-Soulier platelets.
Conclusion
Sialyltransferase activity (GO:0008373) is a fundamental molecular function that governs the addition of sialic acid to glycoproteins and glycolipids, impacting cell signaling, immune recognition, and cancer progression. Its dysregulation is associated with cancer, liver regeneration, and platelet disorders [1,5,6]. Understanding the mechanisms and regulation of sialyltransferase activity is essential for developing targeted therapies and biomarkers. EDITGENE's CRISPR services provide powerful tools to dissect the roles of individual sialyltransferases in health and disease.
References
- 1. Berge PG et al.. 1982. Serum-sialyltransferase activity in cancer patients.. Klin Wochenschr 60(9):445-9 PMID: 7045508
- 2. Sakamoto F et al.. 2026. A novel autopolysialylation activity of the ganglioside sialyltransferase ST8Sia5 regulates its secretion and enzyme activity.. J Biol Chem 302(7):113106 PMID: 42103213
- 3. Shu X et al.. 2023. BRCA1 Insufficiency Induces a Hypersialylated Acidic Tumor Microenvironment That Promotes Metastasis and Immunotherapy Resistance.. Cancer Res 83(15):2614-2633 PMID: 37227919
- 4. Cheng J et al.. 2010. Trans-sialidase activity of Photobacterium damsela alpha2,6-sialyltransferase and its application in the synthesis of sialosides.. Glycobiology 20(2):260-8 PMID: 19880425
- 5. Serafini-Cessi F. 1977. Sialyltransferase activity in regenerating rat liver.. Biochem J 166(3):381-6 PMID: 597233
- 6. Bauvois B et al.. 1981. Glycoprotein-sialyltransferase activity of normal human, thrombasthenic and Bernard-Soulier platelets.. Vox Sang 40(2):71-8 PMID: 6165143
- 7. van Dijk W et al.. 1986. Activity and secretion of sialyltransferase in primary monolayer cultures of rat hepatocytes cultured with and without dexamethasone.. Biochem Cell Biol 64(2):79-84 PMID: 3718701
- 8. Delannoy P et al.. 1993. Sialyltransferase activity in FR3T3 cells transformed with ras oncogene: decreased CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase.. Glycoconj J 10(1):91-8 PMID: 8358231
