GO:0047233 N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0047233 describes the enzymatic transfer of N-acetylgalactosamine (GalNAc) from UDP-GalNAc to an N-acetylneuraminylgalactosylglucosylceramide acceptor, forming the Sda blood group antigen.
• The enzyme responsible is B4GALNT2 (beta-1,4-N-acetylgalactosaminyltransferase 2), which adds GalNAc in a beta-1,4 linkage to the NeuAc alpha2,3Gal beta-R acceptor.
• B4GALNT2 activity is critical for Sda antigen expression, which influences immune recognition and has been linked to xenotransplantation rejection [1,6].
• The enzyme is a Golgi-resident type II membrane protein, and its activity depends on correct N-glycosylation and localization.
• CRISPR-Cas9 knockout of B4GALNT2 in pigs reduces xenoreactive antigenicity and improves compatibility for xenotransplantation [1,6].
• Research on GO:0047233 uses knockout, point mutation, knock-in, and overexpression models to dissect its role in glycosylation, immunity, and cancer.
Description
GO:0047233, N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity, is a molecular function that catalyzes the transfer of N-acetylgalactosamine (GalNAc) from UDP-GalNAc to an N-acetylneuraminylgalactosylglucosylceramide acceptor, producing a beta-1,4-linked GalNAc derivative and releasing UDP and H+. This activity is essential for the biosynthesis of the Sda blood group antigen, a carbohydrate epitope expressed on glycoproteins and glycolipids in various tissues. The enzyme responsible, B4GALNT2, is a Golgi-resident glycosyltransferase that plays a key role in cell surface glycosylation and immune recognition. Understanding this activity is important for researchers studying glycosylation, immune responses, and xenotransplantation, as it directly affects the antigenic profile of cells and tissues [1,6]. The Sda antigen is also implicated in cancer biology, where altered glycosylation can influence tumor progression and immune evasion. Thus, GO:0047233 represents a critical enzymatic step linking carbohydrate metabolism to immune and disease processes.
N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity At A Glance
| GO ID | GO:0047233 |
|---|---|
| GO term | N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity |
| Ontology | molecular_function |
| Synonym | UDP-N-acetyl-D-galactosamine:N-acetylneuraminyl-2,3-alpha-D-galactosyl-1,4-beta-D-glucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity; uridine diphosphoacetylgalactosamine-acetylneuraminyl(alpha2->3)galactosyl(beta1->4)glucosyl beta1->4-acetylgalactosaminyltransferase activity |
| Major function | Transfer of GalNAc to form Sda antigen |
| Enzyme | B4GALNT2 (beta-1,4-N-acetylgalactosaminyltransferase 2) |
| Substrates | UDP-GalNAc and N-acetylneuraminylgalactosylglucosylceramide derivative |
| Products | Sda antigen derivative, UDP, H+ |
| Cellular location | Golgi apparatus |
What Is GO:0047233?
In simple terms, GO:0047233 is the enzyme activity that adds a specific sugar molecule (GalNAc) to a glycolipid or glycoprotein precursor, creating the Sda antigen. According to QuickGO, it catalyzes the reaction: an N-acetyl-alpha-neuraminyl-(2->3)-beta-D-galactosyl derivative + UDP-N-acetyl-alpha-D-galactosamine = an N-acetyl-beta-D-galactosaminyl-(1->4)-[N-acetyl-alpha-neuraminyl-(2->3)]-beta-D-galactosyl derivative + UDP + H+. This activity is synonymous with UDP-N-acetyl-D-galactosamine:N-acetylneuraminyl-2,3-alpha-D-galactosyl-1,4-beta-D-glucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity and uridine diphosphoacetylgalactosamine-acetylneuraminyl(alpha2->3)galactosyl(beta1->4)glucosyl beta1->4-acetylgalactosaminyltransferase activity. It is a molecular function that modifies glycoconjugates, impacting cell surface properties and recognition.
Why Is N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity Important in Cell Biology?
GO:0047233 is important because it governs the synthesis of the Sda antigen, a carbohydrate structure that modulates cell-cell and cell-matrix interactions and is involved in immune recognition. Dysregulation of this activity can lead to altered glycosylation patterns associated with cancer progression and immune evasion. In xenotransplantation, the presence of Sda and other xenoantigens triggers human immune responses, making B4GALNT2 a target for genetic engineering to reduce rejection [1,6]. Additionally, the enzyme's activity is influenced by its N-glycosylation state, affecting its stability and localization, which has implications for basic cell biology and therapeutic development.
• Sda antigen biosynthesis: GO:0047233 is the final step in Sda antigen synthesis, a blood group-related carbohydrate epitope.
• Immune recognition: Sda antigen can be recognized by antibodies, influencing immune responses in transfusion and transplantation.
• Xenotransplantation: Knockout of B4GALNT2 reduces porcine xenoantigenicity, improving graft survival [1,6].
• Cancer biology: Altered Sda expression is observed in colon carcinoma and other cancers, affecting cell adhesion and metastasis.
• Glycosylation regulation: The enzyme's activity is modulated by its own N-glycosylation, linking glycosylation pathways.
• CRISPR applications: B4GALNT2 is a target for gene editing to create hypoimmunogenic cells for therapy [1,6].
• Research tool: Studying GO:0047233 helps understand Golgi glycosyltransferase function and specificity.
• Biomarker potential: Sda antigen levels may serve as a marker for certain cancers and immune disorders.
What Happens During N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity?
Substrate Recognition and Binding
In simple terms: The enzyme grabs the sugar donor and the acceptor molecule.
The enzyme B4GALNT2 binds to its donor substrate UDP-GalNAc and the acceptor substrate, an N-acetylneuraminylgalactosylglucosylceramide derivative, within the Golgi lumen. The acceptor typically contains a terminal NeuAc alpha2,3Gal beta sequence, which is recognized by the enzyme's catalytic domain. This binding is essential for the subsequent transfer reaction.
Catalytic Transfer of GalNAc
In simple terms: The enzyme moves GalNAc from UDP-GalNAc onto the acceptor.
The catalytic mechanism involves the transfer of GalNAc from UDP-GalNAc to the acceptor substrate, forming a beta-1,4 linkage between GalNAc and the galactose residue of the acceptor. This reaction releases UDP and a proton (H+). The enzyme belongs to the glycosyltransferase family 2 and uses an inverting mechanism, though detailed structural studies are limited.
Product Formation and Sda Antigen Expression
In simple terms: The new sugar structure becomes the Sda antigen on the cell surface.
The product of the reaction is an N-acetyl-beta-D-galactosaminyl-(1->4)-[N-acetyl-alpha-neuraminyl-(2->3)]-beta-D-galactosyl derivative, which constitutes the Sda antigen. This antigen is expressed on glycoproteins and glycolipids and can be detected by specific antibodies. Its presence affects cell surface properties and interactions with lectins and antibodies.
Regulation by N-Glycosylation and Localization
In simple terms: The enzyme's own sugar coating affects how well it works.
B4GALNT2 activity is influenced by its N-glycosylation status. A non-consensus N-X-C glycosylation site impacts the enzyme's activity, stability, and localization to the Golgi. Proper N-glycosylation is required for optimal enzymatic function, and mutations at this site can reduce Sda antigen synthesis.
Key Genes Involved in GO:0047233 N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity
The following genes are directly or indirectly involved in GO:0047233 activity, including the enzyme itself, related glycosyltransferases, and genes affecting substrate availability or immune recognition.
| Gene | Major Role | Research Relevance |
|---|---|---|
| B4GALNT2 | Encodes beta-1,4-N-acetylgalactosaminyltransferase 2, the enzyme responsible for GO:0047233 | Directly catalyzes Sda antigen synthesis; target for knockout in xenotransplantation [1,4] |
| GGTA1 | Encodes alpha-1,3-galactosyltransferase, produces Gal antigen | Knockout reduces hyperacute rejection in xenotransplantation [1,6] |
| CMAH | Encodes CMP-N-acetylneuraminic acid hydroxylase, produces Neu5Gc | Knockout reduces human antibody binding in xenotransplantation [1,6] |
| B4GALNT1 | Encodes beta-1,4-N-acetylgalactosaminyltransferase 1, synthesizes GM2/GD2 gangliosides | Related glycosyltransferase with different acceptor specificity |
| ST3GAL1 | Encodes alpha-2,3-sialyltransferase, creates NeuAc alpha2,3Gal acceptor | Provides substrate for B4GALNT2 |
| ST3GAL2 | Encodes alpha-2,3-sialyltransferase, creates NeuAc alpha2,3Gal acceptor | Provides substrate for B4GALNT2 |
| UGCG | Encodes UDP-glucose ceramide glucosyltransferase, synthesizes glucosylceramide | Provides precursor for glycolipid acceptors |
| B3GALT4 | Encodes beta-1,3-galactosyltransferase, elongates glycolipids | May influence acceptor availability |
| B4GALT5 | Encodes beta-1,4-galactosyltransferase, synthesizes lactosylceramide | Provides precursor for sialylated acceptors |
| FUT1 | Encodes fucosyltransferase, synthesizes H antigen | Competes with sialylation pathways |
| FUT2 | Encodes fucosyltransferase, synthesizes Lewis antigens | Affects glycosylation competition |
| GCNT1 | Encodes core 2 beta-1,6-N-acetylglucosaminyltransferase | Modifies O-glycans, may affect Sda presentation |
| SLC35A1 | Encodes CMP-sialic acid transporter | Affects sialic acid availability for acceptor synthesis |
| SLC35A2 | Encodes UDP-galactose transporter | Affects galactose availability |
| SLC35A3 | Encodes UDP-GalNAc transporter | Affects UDP-GalNAc availability for B4GALNT2 |
| hCD46 | Human complement regulatory protein | Transgenic expression reduces complement-mediated rejection |
| hCD55 | Human complement regulatory protein | Transgenic expression reduces complement-mediated rejection |
| hCD59 | Human complement regulatory protein | Transgenic expression reduces complement-mediated rejection |
How Is N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity Regulated?
B4GALNT2 activity is regulated at multiple levels. Its N-glycosylation at a non-consensus N-X-C site is critical for activity, stability, and Golgi localization. The enzyme competes with other glycosyltransferases for common acceptor substrates, such as the NeuAc alpha2,3Gal beta structure, which can also be modified by fucosyltransferases or sialyltransferases. Additionally, the availability of UDP-GalNAc, transported into the Golgi by SLC35A3, influences enzymatic rate. In cancer, altered expression of B4GALNT2 and its substrates can lead to changes in Sda antigen levels, affecting cell adhesion and signaling.
N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| B4GALNT2 | Colon carcinoma, altered Sda expression | Knockout in CaCo-2 cells |
| B4GALNT2 | Xenotransplantation rejection | Knockout in porcine endothelial cells [1,8] |
| GGTA1 | Hyperacute rejection in xenotransplantation | Knockout in pigs [1,6] |
| CMAH | Xenogeneic immune response | Knockout in pigs [1,6] |
| B4GALNT2 | Sda-negative blood phenotype | Point mutation knock-in in cell lines |
Cancer and Altered Glycosylation
Altered expression of B4GALNT2 and Sda antigen has been observed in colon carcinoma cell lines, where the enzyme was first characterized. Changes in Sda antigen levels can affect cell adhesion, migration, and immune recognition, potentially contributing to tumor progression and metastasis. The enzyme's activity may also influence signaling pathways through glycosphingolipid-mediated interactions.
Xenotransplantation Rejection
In pig-to-human xenotransplantation, the Sda antigen is one of several xenoantigens that trigger human antibody-mediated rejection [1,6]. Knockout of B4GALNT2 in donor pigs, along with other genes like GGTA1 and CMAH, reduces human antibody binding and complement activation, improving graft survival [1,6]. This makes B4GALNT2 a key target for genetic engineering in xenotransplantation.
Immune Disorders and Transfusion Medicine
The Sda antigen is a blood group-related structure, and antibodies against Sda can cause transfusion reactions. Understanding GO:0047233 activity helps in characterizing Sda-negative phenotypes and their clinical implications. Additionally, Sda expression on leukocytes may influence immune cell interactions.
From N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does B4GALNT2 loss reduce Sda antigen? | B4GALNT2 knockout cell line (e.g., CaCo-2) |
| Does N-glycosylation affect enzyme activity? | Point mutation at N-X-C site in B4GALNT2 |
| Can Sda antigen be restored? | Knock-in of wild-type B4GALNT2 |
| Does B4GALNT2 overexpression increase Sda? | Overexpression of B4GALNT2 in HEK293 cells |
| Does B4GALNT2 knockout reduce xenoreactivity? | B4GALNT2 knockout porcine endothelial cells [1,8] |
| Can CRISPRa enhance B4GALNT2 expression? | CRISPRa-SAM system in porcine cells |
How to Study the N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay with UDP-GalNAc | B4GALNT2 catalytic activity | Kinetic studies and inhibitor screening |
| Mass spectrometry | Sda antigen structure and quantity | Glycomic profiling of cells and tissues |
| Flow cytometry with anti-Sda | Cell surface Sda expression | Knockout validation and overexpression analysis |
| Western blot | B4GALNT2 protein levels | Assessing expression and stability |
| Immunofluorescence | Subcellular localization of B4GALNT2 | Golgi localization studies |
| CRISPR knockout | Gene function loss | Xenotransplantation and cancer models [1,6] |
| CRISPRa | Gene activation | Enhancing B4GALNT2 expression |
| RNA-seq | Transcriptional changes | Pathway analysis in edited cells |
Glycosyltransferase Activity Assays
Enzymatic activity of B4GALNT2 can be measured using radioactive or fluorescent UDP-GalNAc and acceptor substrates, followed by product separation by chromatography or mass spectrometry. These assays quantify the transfer of GalNAc to the acceptor, reflecting GO:0047233 activity.
Glycan Analysis by Mass Spectrometry
Mass spectrometry of glycans released from glycoproteins or glycolipids can detect the Sda antigen structure and quantify its abundance. This method provides direct evidence of B4GALNT2 activity in cells and tissues.
Antibody-Based Detection
Monoclonal antibodies against Sda antigen can be used in flow cytometry, immunofluorescence, or Western blotting to assess Sda expression on cell surfaces. This is a rapid way to evaluate B4GALNT2 activity in knockout or overexpression models.
CRISPR Screening and Bioinformatics
Genome-wide CRISPR knockout screens can identify genes that regulate Sda antigen expression, including B4GALNT2 and its substrate transporters [1,6]. Bioinformatics analysis of glycosylation pathways can predict off-target effects and guide experimental design.
How CRISPR Can Be Used to Study GO:0047233 N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity
Knockout
CRISPR-Cas9 knockout of B4GALNT2 eliminates GO:0047233 activity, resulting in loss of Sda antigen expression [1,6]. This is used to reduce xenoantigenicity in porcine cells and to study the role of Sda in cancer cell adhesion [1,4].
Point Mutation
Point mutations can be introduced into B4GALNT2 to disrupt its N-glycosylation site, affecting enzyme activity, stability, and localization. Such models help dissect the importance of specific residues for GO:0047233 function.
Knock-in
Knock-in of wild-type or tagged B4GALNT2 allows for restoration of Sda antigen expression and tracking of the enzyme in cells. This is useful for rescue experiments and localization studies.
Overexpression
Overexpression of B4GALNT2 via CRISPRa or lentiviral vectors increases Sda antigen levels, enabling studies on the effects of enhanced GO:0047233 activity in cell signaling and immune recognition.
How EDITGENE Supports N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity Research
Researchers studying N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in Sda antigen synthesis, immune recognition, or disease progression. EDITGENE provides comprehensive CRISPR-based services to create precise cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity research.
Frequently Asked Questions About N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity
What is GO:0047233?
GO:0047233 is the Gene Ontology term for N-acetylneuraminylgalactosylglucosylceramide beta-1,4-N-acetylgalactosaminyltransferase activity, an enzyme that transfers GalNAc to form the Sda antigen.
What gene encodes the enzyme for GO:0047233?
The enzyme is encoded by B4GALNT2 (beta-1,4-N-acetylgalactosaminyltransferase 2).
What is the Sda antigen?
The Sda antigen is a carbohydrate epitope synthesized by B4GALNT2, expressed on glycoproteins and glycolipids, and involved in immune recognition.
How is B4GALNT2 regulated?
B4GALNT2 is regulated by N-glycosylation at a non-consensus N-X-C site, which affects its activity, stability, and Golgi localization.
What diseases are associated with B4GALNT2?
B4GALNT2 and Sda antigen are associated with colon carcinoma, xenotransplantation rejection, and blood group-related immune reactions [1,4,6].
How can I study GO:0047233 activity?
You can study it using enzymatic assays, mass spectrometry, antibody-based detection, and CRISPR knockout or overexpression models.
What is the role of B4GALNT2 in xenotransplantation?
Knockout of B4GALNT2 in pigs reduces xenoantigenicity and human antibody binding, improving graft compatibility [1,6].
Can CRISPR be used to edit B4GALNT2?
Yes, CRISPR-Cas9 can knockout, point-mutate, knock-in, or overexpress B4GALNT2 in various cell types [1,2,3].
What are the substrates of B4GALNT2?
The substrates are UDP-GalNAc and an N-acetylneuraminylgalactosylglucosylceramide derivative.
Where is B4GALNT2 located in the cell?
B4GALNT2 is a Golgi-resident type II membrane protein.
Conclusion
GO:0047233 represents a key enzymatic activity in glycosylation, responsible for Sda antigen synthesis and influencing immune recognition, cancer biology, and xenotransplantation. Understanding its mechanism, regulation, and disease associations is essential for developing therapeutic strategies. EDITGENE provides advanced CRISPR services to create precise cell models for studying this activity and its related genes, empowering researchers to uncover new insights.
References
- 1. Wang J et al.. 2025. Production and Functional Verification of 8-Gene (GGTA1, CMAH, β4GalNT2, hCD46, hCD55, hCD59, hTBM, hCD39)-Edited Donor Pigs for Xenotransplantation.. Cell Prolif 58(9):e70028 PMID: 40190036
- 2. Cogez V et al.. 2023. N-Glycan on the Non-Consensus N-X-C Glycosylation Site Impacts Activity, Stability, and Localization of the Sd(a) Synthase B4GALNT2.. Int J Mol Sci 24(4) PMID: 36835549
- 3. Jiang J et al.. 2019. Porcine antiviral activity is increased by CRISPRa-SAM system.. Biosci Rep 39(8) PMID: 31371630
- 4. Malagolini N et al.. 1991. UDP-GalNAc:NeuAc alpha 2,3Gal beta-R (GalNAc to Gal) beta 1,4-N-acetylgalactosaminyltransferase responsible for the Sda specificity in human colon carcinoma CaCo-2 cell line.. Biochem Biophys Res Commun 180(2):681-6 PMID: 1953740
- 6. Xu J et al.. 2024. Elimination of GGTA1, CMAH, β4GalNT2 and CIITA genes in pigs compromises human versus pig xenogeneic immune reactions.. Animal Model Exp Med 7(4):584-590 PMID: 38962826
- 8. Li P et al.. 2021. Genetic engineering of porcine endothelial cell lines for evaluation of human-to-pig xenoreactive immune responses.. Sci Rep 11(1):13131 PMID: 34162938
