GO:0052767 mannosyl-oligosaccharide 1,6-alpha-mannosidase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0052767 describes the enzymatic activity that hydrolyzes alpha-(1->6) bonds of alpha-D-mannose residues in mannosyl-oligosaccharides, a key step in N-glycan processing.
• This activity is attributed to class II alpha-mannosidases, particularly Golgi alpha-mannosidase II (MAN2A1) and its isotype MAN2A2 (alpha-mannosidase IIX) [3,6].
• Golgi alpha-mannosidase II is a validated drug target in cancer and diabetes, with numerous inhibitors developed based on its catalytic mechanism [1,2,8].
• The enzyme requires zinc and a specific protonation state for catalysis, and its inhibition can block the formation of complex N-glycans [1,3].
• Dysregulation of alpha-mannosidase II activity is linked to tumor progression, metastasis, and congenital disorders of glycosylation [3,6].
• CRISPR-based knockout, point mutation, and knock-in models are essential to dissect the precise roles of MAN2A1 and MAN2A2 in health and disease.
Description
Mannosyl-oligosaccharide 1,6-alpha-mannosidase activity (GO:0052767) is a molecular function that catalyzes the hydrolysis of alpha-(1->6) linkages of alpha-D-mannose residues within mannosyl-oligosaccharides. This activity is a critical step in the N-linked glycosylation pathway, where it trims specific mannose residues to allow the maturation of glycoproteins into complex or hybrid forms [3,4]. The enzyme responsible, Golgi alpha-mannosidase II (MAN2A1), and its isotype MAN2A2, are type II membrane proteins localized to the Golgi apparatus [3,6]. Researchers study this activity because it influences protein folding, cell signaling, and immune recognition, and its dysregulation is implicated in cancer and genetic disorders [3,6]. The unique catalytic mechanism, involving a zinc ion and a nucleophilic water molecule, has made it a target for inhibitor design [1,2,8].
mannosyl-oligosaccharide 1,6-alpha-mannosidase activity At A Glance
| GO ID | GO:0052767 |
|---|---|
| GO term | mannosyl-oligosaccharide 1,6-alpha-mannosidase activity |
| Ontology | molecular_function |
| Synonym | 1,6-alpha-mannosidase activity; 1,6-alpha-mannosyl-oligosaccharide alpha-D-mannohydrolase activity; alpha-1,6-mannosidase activity; alpha-1,6-mannosyl-oligosaccharide alpha-D-mannohydrolase activity |
| Major function | Hydrolysis of alpha-(1->6) bonds of alpha-D-mannose residues in mannosyl-oligosaccharides |
| EC number | 3.2.1.113 (inferred from related activity) |
| Cellular location | Golgi apparatus (for class II alpha-mannosidases) |
| Representative genes | MAN2A1, MAN2A2 |
What Is GO:0052767?
According to the Gene Ontology, GO:0052767 is defined as the catalysis of the hydrolysis of the alpha-(1->6) bonds of alpha-D-mannose residues in mannosyl-oligosaccharide. In simpler terms, it is an enzyme activity that cuts specific mannose sugars from larger sugar chains, specifically at the 1,6 linkage, using water to break the bond. This activity is synonymous with 1,6-alpha-mannosidase, alpha-1,6-mannosidase, and related terms.
Why Is mannosyl-oligosaccharide 1,6-alpha-mannosidase activity Important in Cell Biology?
Mannosyl-oligosaccharide 1,6-alpha-mannosidase activity is essential for the processing of N-linked glycans, which decorate many cell surface and secreted proteins. This activity determines whether glycoproteins acquire complex or hybrid N-glycans, affecting their stability, trafficking, and interactions [3,4]. Because altered glycosylation is a hallmark of cancer and congenital disorders, understanding this enzyme activity provides insights into disease mechanisms and therapeutic opportunities [3,6].
• It is a key step in N-glycan maturation, influencing protein folding and function.
• Golgi alpha-mannosidase II is overexpressed in several cancers and correlates with metastasis.
• Inhibitors of this activity are being developed as anticancer and antidiabetic agents [1,2,8].
• Mutations in MAN2A1 or MAN2A2 can lead to congenital disorders of glycosylation.
• The enzyme's unique mechanism makes it a model for studying glycoside hydrolases.
• It affects immune recognition by modulating glycan epitopes on cell surfaces.
• Its activity is required for the formation of complex N-glycans on therapeutic glycoproteins.
• It is a potential biomarker for cancer diagnosis and prognosis.
• Studying this activity helps understand Golgi function and vesicular transport.
• It is a target for drug discovery, with many inhibitors characterized structurally [1,2,8].
What Happens During mannosyl-oligosaccharide 1,6-alpha-mannosidase activity?
Substrate Recognition and Binding
In simple terms: The enzyme grabs a sugar chain and positions it so that a specific mannose can be cut off.
The enzyme recognizes mannosyl-oligosaccharides, typically the GlcNAcMan5GlcNAc2 intermediate in N-glycan processing, and binds the substrate in its active site. The binding involves interactions with the mannose residues and the protein backbone, ensuring specificity for the alpha-(1->6) linkage.
Catalytic Hydrolysis
In simple terms: A water molecule breaks the bond between the mannose and the rest of the sugar chain.
Catalysis proceeds via a two-step mechanism involving a nucleophilic water molecule and a general acid/base residue. The zinc ion in the active site polarizes the water, facilitating attack on the anomeric carbon of the alpha-(1->6)-linked mannose, leading to hydrolysis and release of the mannose residue.
Product Release and Processing Continuation
In simple terms: After the mannose is removed, the trimmed sugar chain is ready for further modifications.
The product, a mannosyl-oligosaccharide with one fewer mannose, is released from the enzyme. This trimmed glycan can then be further processed by other glycosyltransferases and mannosidases to form complex N-glycans [3,4].
Key Genes Involved in GO:0052767 mannosyl-oligosaccharide 1,6-alpha-mannosidase activity
The following genes encode proteins that exhibit or regulate mannosyl-oligosaccharide 1,6-alpha-mannosidase activity, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MAN2A1 | Encodes Golgi alpha-mannosidase II, the primary enzyme for this activity | Target for cancer and diabetes; knockout models show loss of complex N-glycans |
| MAN2A2 | Encodes alpha-mannosidase IIX, an isotype with similar activity | Implicated in congenital disorders; tissue-specific functions |
| MAN2C1 | Encodes cytosolic alpha-mannosidase, which can hydrolyze alpha-1,6 linkages | Related to ER-associated degradation and stress responses |
| MAN2B1 | Encodes lysosomal alpha-mannosidase, involved in glycoprotein catabolism | Deficiency causes alpha-mannosidosis, a lysosomal storage disease |
| MAN1A1 | Encodes Golgi alpha-1,2-mannosidase IA, upstream of MAN2A1 | Affects N-glycan trimming and substrate availability |
| MAN1A2 | Encodes Golgi alpha-1,2-mannosidase IB | Similar to MAN1A1, contributes to glycan processing |
| MAN1B1 | Encodes ER alpha-1,2-mannosidase I | Involved in ER quality control and N-glycan trimming |
| MAN1C1 | Encodes Golgi alpha-1,2-mannosidase IC | May compensate for other mannosidases |
| MANBA | Encodes beta-mannosidase, acts on beta-linked mannose | Deficiency causes beta-mannosidosis |
| GMII | Alternative name for Golgi alpha-mannosidase II (MAN2A1) | Commonly used in inhibitor studies [1,2,8] |
| MAN2A1-like | Insect class II alpha-mannosidase with unique properties | Model for studying enzyme evolution |
| KIFUNENSINE | Not a gene; a potent inhibitor of class I alpha-mannosidases | Used to probe mannosidase function |
| SWAINSONINE | Not a gene; an inhibitor of Golgi alpha-mannosidase II | Tool compound for studying N-glycan processing |
| Zinc ion | Cofactor required for catalysis | Essential for enzyme activity |
| GlcNAcMan5GlcNAc2 | Substrate for MAN2A1 | Intermediate in N-glycan pathway |
| MAN2A1 promoter | Regulatory region controlling expression | Transcriptional regulation studied in cancer |
| MAN2A2 promoter | Regulatory region for isotype expression | Tissue-specific regulation |
| ER alpha-mannosidase | Kifunensine-resistant enzyme related to cytosolic mannosidase | May act on misfolded glycoproteins |
How Is mannosyl-oligosaccharide 1,6-alpha-mannosidase activity Regulated?
The activity of mannosyl-oligosaccharide 1,6-alpha-mannosidase is primarily regulated at the level of gene expression and subcellular localization. Transcription of MAN2A1 and MAN2A2 is controlled by tissue-specific factors and can be altered in cancer. The enzyme's activity is also influenced by the availability of substrates and cofactors, such as zinc, and by the Golgi environment. Inhibitors like swainsonine can acutely modulate activity.
mannosyl-oligosaccharide 1,6-alpha-mannosidase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MAN2A1 | Cancer metastasis, hepatocellular carcinoma | Knockout in cancer cell lines; xenograft models |
| MAN2A2 | Congenital disorder of glycosylation | Patient-derived fibroblasts; knock-in mouse models |
| MAN2C1 | ER stress response, diabetes | Knockout in pancreatic beta cells |
| MAN2B1 | Alpha-mannosidosis | Lysosomal storage disease models |
| MAN1B1 | ER quality control, neurodegeneration | Neuronal knockout models |
Cancer
Overexpression of MAN2A1 and increased Golgi alpha-mannosidase II activity are observed in various cancers, including hepatocellular carcinoma and melanoma, where they promote metastasis by altering cell surface glycans. Inhibitors of this activity reduce tumor growth in preclinical models [1,2].
Congenital Disorders of Glycosylation
Mutations in MAN2A2 have been linked to congenital disorders of glycosylation, characterized by developmental delay and neurological impairment. Defects in N-glycan processing due to altered mannosidase activity can lead to multisystemic disease.
Diabetes and Metabolic Disorders
Golgi alpha-mannosidase II inhibitors improve glucose tolerance in diabetic animal models, suggesting a role for this activity in insulin signaling and glucose homeostasis [1,8].
From mannosyl-oligosaccharide 1,6-alpha-mannosidase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of MAN2A1 affect tumor growth? | MAN2A1 knockout in cancer cell lines and mouse xenografts |
| What is the role of MAN2A2 in development? | MAN2A2 knockout mouse |
| Can a point mutation in the catalytic site abolish activity? | CRISPR knock-in of catalytic dead mutant |
| How does MAN2A1 overexpression alter glycan profiles? | MAN2A1 overexpression in HEK293 cells |
| Does MAN2A1 inhibition improve insulin sensitivity? | Inducible knockout in mouse liver |
| What are the off-target effects of mannosidase inhibitors? | CRISPR knockout of MAN2A1 and MAN2A2 in cell lines |
How to Study the mannosyl-oligosaccharide 1,6-alpha-mannosidase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay with fluorogenic substrate | Mannosidase activity | Screening inhibitors, measuring kinetic parameters |
| LC-MS glycan profiling | N-glycan structures | Assessing effects of knockout or inhibitors |
| CRISPR-Cas9 knockout | Gene function | Creating loss-of-function models |
| CRISPR knock-in | Specific mutations | Studying catalytic residues |
| Western blot | Protein expression | Validating knockout or overexpression |
| Immunofluorescence | Subcellular localization | Confirming Golgi localization |
| Activity-based protein profiling | Active enzyme levels | Discovering new inhibitors |
| X-ray crystallography | 3D structure | Understanding mechanism and inhibitor binding |
Enzymatic Activity Assays
Fluorogenic or chromogenic substrates, such as 4-methylumbelliferyl-alpha-D-mannopyranoside, are used to measure mannosyl-oligosaccharide 1,6-alpha-mannosidase activity in cell lysates or purified enzyme preparations. These assays can be adapted for high-throughput screening of inhibitors.
Glycan Profiling
Mass spectrometry and HPLC-based glycan profiling are used to determine the effects of altered mannosidase activity on N-glycan structures. Knockout or inhibitor-treated cells show accumulation of high-mannose or hybrid glycans [3,4].
CRISPR-Cas9 Genome Editing
CRISPR-Cas9 is used to generate knockout, point mutation, and knock-in cell models to study the function of MAN2A1 and MAN2A2. These models enable precise dissection of enzyme activity in cellular processes.
Structural Biology
X-ray crystallography and cryo-EM provide insights into the catalytic mechanism and inhibitor binding of Golgi alpha-mannosidase II, guiding drug design.
How CRISPR Can Be Used to Study GO:0052767 mannosyl-oligosaccharide 1,6-alpha-mannosidase activity
Knockout
CRISPR-Cas9 knockout of MAN2A1 or MAN2A2 in cell lines abolishes mannosyl-oligosaccharide 1,6-alpha-mannosidase activity, leading to accumulation of hybrid N-glycans and altered cell surface glycosylation. These models are used to study the role of the enzyme in cancer and development.
Point Mutation
Introducing point mutations in the catalytic domain of MAN2A1 via CRISPR knock-in allows researchers to dissect the contribution of specific residues to catalysis and to create enzyme-dead variants for functional studies.
Knock-in
Knock-in of epitope tags or fluorescent proteins into the endogenous MAN2A1 locus enables real-time imaging and proteomic analysis of the enzyme in its native context.
Overexpression
CRISPR activation or lentiviral overexpression of MAN2A1 is used to study the effects of increased enzyme activity on glycan processing and cell behavior, such as migration and invasion.
How EDITGENE Supports mannosyl-oligosaccharide 1,6-alpha-mannosidase activity Research
Researchers studying mannosyl-oligosaccharide 1,6-alpha-mannosidase activity-related genes often need to determine whether a candidate gene is causally involved in glycan processing, cancer progression, or metabolic disease. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for mannosyl-oligosaccharide 1,6-alpha-mannosidase activity research.
Frequently Asked Questions About mannosyl-oligosaccharide 1,6-alpha-mannosidase activity
What is mannosyl-oligosaccharide 1,6-alpha-mannosidase activity?
It is an enzyme activity that removes a specific mannose sugar (alpha-1,6-linked) from N-linked glycans, as defined by GO:0052767.
What genes are involved in mannosyl-oligosaccharide 1,6-alpha-mannosidase activity?
The main genes are MAN2A1 and MAN2A2, which encode Golgi alpha-mannosidase II and IIX, respectively [3,6].
What diseases are associated with this activity?
Altered activity is linked to cancer metastasis, congenital disorders of glycosylation, and diabetes [3,6].
How is mannosyl-oligosaccharide 1,6-alpha-mannosidase activity measured?
It is typically measured using fluorogenic substrates or by glycan profiling with mass spectrometry.
What are inhibitors of this enzyme?
Swainsonine and manno-epi-cyclophellitols are known inhibitors of Golgi alpha-mannosidase II [2,3].
What is the role of MAN2A1 in cancer?
MAN2A1 overexpression promotes cancer metastasis by altering cell surface glycans.
Can CRISPR be used to study this activity?
Yes, CRISPR knockout, knock-in, and point mutation models are powerful tools to dissect gene function.
What is the cellular location of this activity?
It occurs primarily in the Golgi apparatus, mediated by class II alpha-mannosidases.
What is the difference between MAN2A1 and MAN2A2?
They are isotypes with similar activity but different tissue distribution and regulation.
How does mannosyl-oligosaccharide 1,6-alpha-mannosidase activity affect glycoproteins?
It trims mannose residues to allow the formation of complex N-glycans, affecting protein folding and function [3,4].
Conclusion
Mannosyl-oligosaccharide 1,6-alpha-mannosidase activity (GO:0052767) is a fundamental enzymatic function in N-glycan processing, with critical roles in health and disease. Its main effectors, MAN2A1 and MAN2A2, are implicated in cancer, congenital disorders, and metabolic diseases, making them attractive targets for therapeutic intervention. Advances in CRISPR genome editing and glycan analysis continue to unravel the precise mechanisms and regulatory networks of this activity, offering new opportunities for drug discovery and personalized medicine.
References
- 1. Kóňa J et al.. 2022. 1,4-Dideoxy-1,4-imino-D- and L-lyxitol-based inhibitors bind to Golgi α-mannosidase II in different protonation forms.. Org Biomol Chem 20(45):8932-8943 PMID: 36322142
- 2. Armstrong Z et al.. 2020. Manno-epi-cyclophellitols Enable Activity-Based Protein Profiling of Human α-Mannosidases and Discovery of New Golgi Mannosidase II Inhibitors.. J Am Chem Soc 142(30):13021-13029 PMID: 32605368
- 3. Rose DR. 2012. Structure, mechanism and inhibition of Golgi α-mannosidase II.. Curr Opin Struct Biol 22(5):558-62 PMID: 22819743
- 4. Skudlarek MD et al.. 1991. Asparagine-linked glycoprotein biosynthesis in rat epididymis. Presence of a mannosidase II-like enzyme.. Biochem J 277 ( Pt 1)(Pt 1):213-21 PMID: 1906709
- 5. Weng S et al.. 1996. Endoplasmic reticulum kifunensine-resistant alpha-mannosidase is enzymatically and immunologically related to the cytosolic alpha-mannosidase.. Arch Biochem Biophys 325(1):113-23 PMID: 8554335
- 6. Ogawa R et al.. 1996. Structure and transcriptional regulation of human alpha-mannosidase IIX (alpha-mannosidase II isotype) gene.. Eur J Biochem 242(3):446-53 PMID: 9022667
- 7. Kawar Z et al.. 2001. Insect cells encode a class II alpha-mannosidase with unique properties.. J Biol Chem 276(19):16335-40 PMID: 11279010
- 8. Šesták S et al.. 2018. N-Benzyl Substitution of Polyhydroxypyrrolidines: The Way to Selective Inhibitors of Golgi α-Mannosidase II.. ChemMedChem 13(4):373-383 PMID: 29323461
