GO:0106330 sialate 9-O-acetylesterase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0106330 sialate 9-O-acetylesterase activity catalyzes the hydrolysis of N-acetyl-9-O-acetylneuraminate to acetate, H+, and N-acetylneuraminate.
• The enzyme removes the 9-O-acetyl group from sialic acids, a modification that serves as a receptor determinant for influenza C virus and some coronaviruses.
• Influenza C virus uses a single glycoprotein (HEF) that combines hemagglutinin, esterase, and fusion activities, with a catalytic triad essential for esterase function.
• Both lysosomal and cytosolic forms of sialate 9-O-acetylesterase can be encoded by one gene through alternative use of a signal peptide-encoding exon.
• Inhibitors of viral sialate-O-acetylesterases have been synthesized as potential antiviral agents.
• Detection of 9-O-acetylated sialic acids can be achieved using influenza C virus esterase activity on immobilized glycoconjugates.
Description
Sialate 9-O-acetylesterase activity (GO:0106330) is a molecular function that removes the 9-O-acetyl ester from sialic acids, releasing acetate and free N-acetylneuraminate. This enzymatic activity is critical for modulating the recognition of sialic acids by viruses and for regulating sialic acid biology in eukaryotic cells. Researchers study this activity to understand viral entry mechanisms, host-pathogen interactions, and the role of sialic acid modifications in health and disease. The enzyme is also important because 9-O-acetylated sialic acids serve as receptor determinants for influenza C virus and bovine coronavirus, making the esterase a potential target for antiviral strategies.
sialate 9-O-acetylesterase activity At A Glance
| GO ID | GO:0106330 |
|---|---|
| GO term | sialate 9-O-acetylesterase activity |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Catalysis of the hydrolysis of the 9-O-acetyl group from N-acetyl-9-O-acetylneuraminate, yielding acetate, H+, and N-acetylneuraminate |
| Reaction | H2O + N-acetyl-9-O-acetylneuraminate = acetate + H+ + N-acetylneuraminate |
| Subcellular localization | Lysosomal and cytosolic forms can be encoded by one gene via alternative signal peptide usage |
| Viral counterpart | Influenza C virus HEF glycoprotein possesses this esterase activity |
| Inhibitors | Sialic acid derivatives have been synthesized as inhibitors of viral sialate-O-acetylesterases |
What Is GO:0106330?
Sialate 9-O-acetylesterase activity is defined as the catalysis of the reaction: H2O + N-acetyl-9-O-acetylneuraminate = acetate + H+ + N-acetylneuraminate. In other words, it is an enzyme that hydrolyzes the ester bond at the 9-O-acetyl group of sialic acid, removing the acetyl modification and producing free sialic acid.
Why Is sialate 9-O-acetylesterase activity Important in Cell Biology?
Sialate 9-O-acetylesterase activity is important because it regulates the presence of 9-O-acetylated sialic acids, which are key receptor determinants for influenza C virus and some coronaviruses. By removing the 9-O-acetyl group, the enzyme can abolish viral binding and entry, making it a critical factor in host defense and viral pathogenesis. Additionally, the enzyme is involved in sialic acid catabolism and modification, influencing cellular processes such as cell signaling and immune recognition.
• Modulates viral infection by removing the receptor determinant for influenza C virus and bovine coronavirus.
• Essential for the life cycle of influenza C virus, where the HEF protein combines receptor binding, esterase, and fusion functions.
• Provides a target for antiviral drug development, as inhibitors of viral esterases can block infection.
• Regulates sialic acid metabolism and the display of 9-O-acetylated sialic acids on cell surfaces.
• Involved in host-pathogen interactions and immune evasion strategies.
• Can be used as a tool to detect 9-O-acetylated sialic acids on glycoconjugates.
• Dysregulation may affect lysosomal and cytosolic sialic acid processing.
• Plays a role in the catalytic mechanism of viral esterases, with a conserved catalytic triad.
Molecular Mechanism of sialate 9-O-acetylesterase activity
Substrate Recognition and Binding
In simple terms: The enzyme recognizes and binds to sialic acid molecules that have an acetyl group attached at the 9th carbon.
Sialate 9-O-acetylesterase specifically binds N-acetyl-9-O-acetylneuraminate, the substrate. The enzyme's active site accommodates the sialic acid moiety, positioning the 9-O-acetyl ester bond for hydrolysis. This specificity ensures that only sialic acids with a 9-O-acetyl modification are targeted, while other sialic acid derivatives are not affected.
Catalytic Hydrolysis
In simple terms: The enzyme uses water to break the ester bond, releasing acetate and free sialic acid.
The catalytic mechanism involves a water molecule that attacks the carbonyl carbon of the 9-O-acetyl ester, leading to the release of acetate and the formation of N-acetylneuraminate. This hydrolysis reaction is essential for removing the acetyl group and is mediated by a catalytic triad of amino acids, as demonstrated in the influenza C virus HEF esterase.
Catalytic Triad and Active Site
In simple terms: Three amino acids work together to perform the chemical reaction.
Site-directed mutagenesis studies of the influenza C virus glycoprotein HEF have identified a catalytic triad (serine, histidine, and aspartate) that is essential for esterase activity. This triad is conserved in viral and potentially cellular sialate 9-O-acetylesterases, and its disruption abolishes enzymatic function.
Regulation and Isoforms
In simple terms: One gene can produce two versions of the enzyme, one that goes to lysosomes and one that stays in the cytosol.
The lysosomal and cytosolic sialic acid 9-O-acetylesterase activities can be encoded by a single gene through differential usage of a signal peptide-encoding exon at the N terminus. This alternative splicing or promoter usage generates isoforms with distinct subcellular localizations, allowing the enzyme to function in different cellular compartments.
Key Genes Involved in GO:0106330 sialate 9-O-acetylesterase activity
The following genes and proteins are directly associated with sialate 9-O-acetylesterase activity, including viral and cellular factors.
| Gene | Major Role | Research Relevance |
|---|---|---|
| HEF (influenza C virus) | Viral glycoprotein with hemagglutinin, esterase, and fusion activities; contains the catalytic triad for 9-O-acetylesterase | Model for studying viral entry and esterase mechanism; target for antiviral inhibitors |
| SIAE (human) | Cellular sialate 9-O-acetylesterase; encodes lysosomal and cytosolic isoforms via alternative signal peptide exon | Studying sialic acid metabolism and 9-O-acetylation in human cells |
| S protein (bovine coronavirus) | Hemagglutinin recognizing 9-O-acetylated sialic acid as receptor determinant | Understanding coronavirus host range and receptor specificity |
| Influenza C virus HEF | Esterase activity removes 9-O-acetyl groups to facilitate viral release | Antiviral target and tool for detecting 9-O-acetylated sialic acids |
| Sialate-O-acetylesterase (viral) | Enzyme that hydrolyzes 9-O-acetyl esters on sialic acids | Screening for inhibitors as antiviral drugs |
| N-acetyl-9-O-acetylneuraminate | Substrate for the esterase reaction | Substrate in enzymatic assays and inhibitor design |
| N-acetylneuraminate | Product of the esterase reaction | Metabolite in sialic acid pathways |
| Acetate | Byproduct of the esterase reaction | Indicator of enzyme activity |
| 9-O-acetylated sialic acid | Receptor determinant for influenza C virus and coronaviruses | Target for viral detection and infection studies |
| HEF esterase domain | Catalytic domain responsible for 9-O-acetylesterase activity | Structural and functional studies |
| Catalytic triad residues (Ser, His, Asp) | Essential for esterase activity in HEF | Mutagenesis studies to probe mechanism |
| SIAE isoform 1 (lysosomal) | Lysosomal sialate 9-O-acetylesterase | Lysosomal sialic acid catabolism research |
| SIAE isoform 2 (cytosolic) | Cytosolic sialate 9-O-acetylesterase | Cytosolic sialic acid processing research |
| Influenza C virus | Uses 9-O-acetylated sialic acid as receptor and esterase for entry/exit | Viral pathogenesis and transmission studies |
| Bovine coronavirus | Recognizes 9-O-acetylated sialic acid via S protein | Coronavirus receptor specificity research |
| Sialic acid derivatives (inhibitors) | Synthetic compounds targeting viral esterases | Antiviral drug development |
How Is sialate 9-O-acetylesterase activity Regulated?
The activity of sialate 9-O-acetylesterase is regulated at multiple levels. In humans, the SIAE gene produces both lysosomal and cytosolic isoforms through differential usage of a signal peptide-encoding exon, which determines subcellular localization and thus access to substrates. Viral esterase activity, such as that of influenza C virus HEF, is regulated by the catalytic triad and potentially by pH and other environmental factors during viral entry and egress. Inhibitors can modulate enzyme activity, as shown by sialic acid derivatives that block viral esterases.
sialate 9-O-acetylesterase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HEF (influenza C virus) | Influenza C virus infection; viral entry and release | KO of HEF esterase activity in viral genome; point mutations in catalytic triad |
| SIAE (human) | Sialic acid metabolism; potential lysosomal storage disorders | Knockout of SIAE in human cell lines; overexpression of isoforms |
| S protein (bovine coronavirus) | Coronavirus receptor recognition | Point mutations in S protein to alter sialic acid binding |
| 9-O-acetylated sialic acid | Viral receptor determinant | Knock-in of sialate 9-O-acetylesterase to remove receptor |
| Sialate-O-acetylesterase inhibitors | Antiviral drug development | Overexpression of viral esterase for inhibitor screening |
Influenza C Virus Infection
Influenza C virus uses 9-O-acetylated sialic acid as a receptor determinant, and its HEF glycoprotein possesses sialate 9-O-acetylesterase activity that is essential for viral entry and release. The esterase removes the receptor to allow viral spread, and inhibitors of this activity can block infection. The catalytic triad of HEF is critical for this process, as mutations abolish esterase function and impair viral replication.
Coronavirus Recognition
Bovine coronavirus and possibly other coronaviruses recognize 9-O-acetylated sialic acid as a receptor determinant via their S protein. The presence of 9-O-acetylated sialic acids on host cells can influence viral tropism and pathogenesis. Sialate 9-O-acetylesterase activity can remove these receptors and potentially modulate coronavirus infection.
Sialic Acid Metabolism Disorders
Defects in sialic acid 9-O-acetylesterase could lead to altered levels of 9-O-acetylated sialic acids, which may impact lysosomal and cytosolic sialic acid catabolism. Although specific diseases are not well-defined, the enzyme's role in sialic acid processing suggests potential involvement in metabolic and immune disorders.
From sialate 9-O-acetylesterase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of sialate 9-O-acetylesterase affect viral infection? | Knockout of SIAE in human cell lines or primary cells |
| What is the role of the catalytic triad in esterase activity? | Point mutations of Ser, His, Asp in HEF |
| Can we visualize 9-O-acetylated sialic acids on cells? | Knock-in of tagged sialate 9-O-acetylesterase for detection |
| Does overexpression of SIAE reduce 9-O-acetylated sialic acids? | Overexpression of SIAE isoforms in cell lines |
| Can inhibitors block viral esterase in vivo? | Overexpression of viral esterase in cell culture for inhibitor testing |
| What is the subcellular localization of SIAE isoforms? | Tagged knock-in of SIAE with fluorescent protein |
How to Study the sialate 9-O-acetylesterase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Esterase activity assay | Hydrolysis of 9-O-acetyl groups | Enzyme kinetics and inhibitor screening |
| Site-directed mutagenesis | Effect of mutations on catalytic activity | Identifying essential residues |
| Viral infection assay | Viral entry and replication | Studying receptor determinants |
| Glycoconjugate detection | Presence of 9-O-acetylated sialic acids | Analyzing sialic acid modifications |
| Western blot | Protein expression of SIAE isoforms | Subcellular localization studies |
| Immunofluorescence | Cellular localization of enzyme | Visualizing lysosomal vs cytosolic isoforms |
| Inhibitor screening | Blocking of esterase activity | Antiviral drug discovery |
| CRISPR knockout | Loss of gene function | Studying cellular roles of SIAE |
Enzymatic Activity Assays
Sialate 9-O-acetylesterase activity can be measured using synthetic substrates such as N-acetyl-9-O-acetylneuraminate, with detection of released acetate or free sialic acid. Influenza C virus esterase activity has been used to detect 9-O-acetylated sialic acids on immobilized glycoconjugates. These assays are essential for characterizing enzyme kinetics and inhibitor efficacy.
Site-Directed Mutagenesis
Mutagenesis of the catalytic triad residues in the influenza C virus HEF protein has been used to confirm their essential role in esterase activity. This approach can be applied to cellular SIAE to probe structure-function relationships.
Viral Infection Models
Influenza C virus and bovine coronavirus infection models are used to study the role of 9-O-acetylated sialic acids as receptors and the impact of esterase activity on viral entry and release. These models help evaluate antiviral inhibitors targeting the esterase.
Glycoconjugate Detection
The esterase activity of influenza C virus can be exploited to detect 9-O-acetylated sialic acids on glycoconjugates, providing a sensitive method for studying sialic acid modifications.
How CRISPR Can Be Used to Study GO:0106330 sialate 9-O-acetylesterase activity
Knockout
CRISPR knockout of SIAE can eliminate sialate 9-O-acetylesterase activity in human cells, allowing researchers to study the accumulation of 9-O-acetylated sialic acids and its effects on viral infection and cellular metabolism. Knockout of viral HEF esterase activity in the context of influenza C virus can be achieved by targeting the catalytic triad, though this requires reverse genetics rather than CRISPR.
Point Mutation
CRISPR-mediated point mutations can be introduced into the catalytic triad residues of SIAE or viral HEF to dissect the enzymatic mechanism and assess the importance of individual amino acids for esterase activity. Such models are valuable for understanding substrate specificity and catalytic efficiency.
Knock-in
Knock-in of tagged SIAE (e.g., with fluorescent or affinity tags) allows visualization and purification of the enzyme, enabling studies of its subcellular localization and interaction partners. Knock-in of a reporter gene under the SIAE promoter can also be used to monitor expression dynamics.
Overexpression
Overexpression of SIAE isoforms in cell lines can increase sialate 9-O-acetylesterase activity, leading to reduced levels of 9-O-acetylated sialic acids and potentially inhibiting viral infection. Overexpression of viral esterase domains is useful for high-throughput inhibitor screening.
How EDITGENE Supports sialate 9-O-acetylesterase activity Research
Researchers studying sialate 9-O-acetylesterase activity-related genes often need to determine whether a candidate gene is causally involved in sialic acid modification, viral entry, or metabolic pathways. EDITGENE provides comprehensive CRISPR-based services to create precise cellular models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for sialate 9-O-acetylesterase activity research.
Frequently Asked Questions About sialate 9-O-acetylesterase activity
What is sialate 9-O-acetylesterase activity?
Sialate 9-O-acetylesterase activity (GO:0106330) is a molecular function that catalyzes the hydrolysis of the 9-O-acetyl group from N-acetyl-9-O-acetylneuraminate, producing acetate, H+, and N-acetylneuraminate.
What genes are involved in sialate 9-O-acetylesterase activity?
The human SIAE gene encodes cellular sialate 9-O-acetylesterase, while the influenza C virus HEF gene encodes a viral glycoprotein with this activity.
How is sialate 9-O-acetylesterase activity related to influenza C virus?
Influenza C virus uses 9-O-acetylated sialic acid as a receptor, and its HEF protein has esterase activity that removes the receptor to facilitate viral entry and release.
What is the reaction catalyzed by sialate 9-O-acetylesterase?
The reaction is: H2O + N-acetyl-9-O-acetylneuraminate = acetate + H+ + N-acetylneuraminate.
Can sialate 9-O-acetylesterase be targeted for antiviral therapy?
Yes, inhibitors of viral sialate-O-acetylesterases have been synthesized and tested as potential antiviral agents.
What is the catalytic mechanism of sialate 9-O-acetylesterase?
It involves a catalytic triad of serine, histidine, and aspartate residues that mediate hydrolysis of the ester bond.
How can I detect 9-O-acetylated sialic acids?
Influenza C virus esterase activity can be used to detect 9-O-acetylated sialic acids on immobilized glycoconjugates.
What are the isoforms of sialate 9-O-acetylesterase?
The enzyme exists as lysosomal and cytosolic isoforms encoded by one gene via differential usage of a signal peptide-encoding exon.
Which viruses recognize 9-O-acetylated sialic acid?
Influenza C virus and bovine coronavirus recognize 9-O-acetylated sialic acid as a receptor determinant.
How can CRISPR be used to study sialate 9-O-acetylesterase activity?
CRISPR knockout, point mutation, knock-in, and overexpression can be used to manipulate SIAE or viral HEF genes to study their function.
Conclusion
Sialate 9-O-acetylesterase activity (GO:0106330) is a key enzymatic function that regulates the 9-O-acetylation status of sialic acids, impacting viral infection and cellular metabolism. Its role as a receptor determinant for influenza C virus and coronaviruses makes it a target for antiviral research. Understanding its mechanism and regulation through CRISPR-based models will continue to provide insights into host-pathogen interactions and sialic acid biology.
References
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- 3. Zimmer G et al.. 1992. Use of influenza C virus for detection of 9-O-acetylated sialic acids on immobilized glycoconjugates by esterase activity.. Eur J Biochem 204(1):209-15 PMID: 1740131
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- 6. Rosenthal PB et al.. 1998. Structure of the haemagglutinin-esterase-fusion glycoprotein of influenza C virus.. Nature 396(6706):92-6 PMID: 9817207
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