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Identification and Characterization of Protein Glycosylation using Specific Endo- and Exoglycosidases
Published on: December 26, 2011
Sugar-assisted glycopeptide ligation with complex oligosaccharides: scope and limitations
Clay S Bennett1, Stephen M Dean, Richard J Payne
1Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|August 14, 2008
Summary
Sugar-assisted ligation (SAL) enables complex glycopeptide synthesis. This study shows SAL works with extended sugars, but C-3 glycosylation blocks ligation, guiding future glycoprotein construction.
Area of Science:
- Carbohydrate Chemistry
- Organic Synthesis
- Glycochemistry
Background:
- Sugar-assisted ligation (SAL) is a valuable method for convergent glycopeptide synthesis.
- Current SAL applications are limited to monosaccharide-based thiol auxiliaries.
- Expanding SAL to complex, naturally occurring glycans is crucial for synthesizing advanced glycopeptides and glycoproteins.
Purpose of the Study:
- To investigate the feasibility of SAL with complex, multi-sugar thiol auxiliaries.
- To determine the impact of glycosylation at C-3, C-4, and C-6 positions on SAL efficiency.
- To establish guidelines for employing SAL in the synthesis of intricate glycopeptides and glycoproteins.
Main Methods:
- Chemoenzymatic synthesis of model glycopeptides with varying glycosylation patterns.
- Reaction of synthesized glycopeptides with peptide thioesters using the SAL methodology.
- Analysis of ligation efficiency based on the position and extent of glycosylation on the thiol auxiliary.
Main Results:
- SAL is sensitive to extended glycosylation on the auxiliary-containing glycan.
- Ligation is successful with glycosylation at C-4 and C-6 positions.
- Glycosylation at the C-3 position completely inhibits the SAL reaction.
- SAL efficiency with C-4 glycosylation is influenced by the N-terminal amino acid of the peptide thioester.
- The C-terminal residue of the peptide thioester does not significantly impact ligation efficiency.
Conclusions:
- SAL can be adapted for use with more complex, extended sugar structures.
- Glycosylation at C-3 is a critical factor that prevents SAL, necessitating careful selection of ligation sites.
- Understanding these constraints allows for strategic application of SAL in synthesizing complex glycopeptides and glycoproteins.
- These findings provide essential guidance for optimizing SAL yields in complex carbohydrate-based synthesis.
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