Structural and immunochemical analysis of three alpha-limit dextrin oligosaccharides

Area of Science:

• Biochemistry
• Glycogen Metabolism
• Immunology

Background:

• Glycogen storage diseases (GSDs) involve defects in glycogen metabolism, leading to abnormal glycogen accumulation.
• Urinary excretion of oligosaccharides can serve as biomarkers for metabolic disorders.
• Understanding the structure and properties of these oligosaccharides is crucial for diagnosis and research.

Purpose of the Study:

• To elucidate the complete structures of three urinary oligosaccharides found in patients with Type II and Type III glycogen storage diseases.
• To investigate the binding affinities of these oligosaccharides to a specific monoclonal antibody.
• To explore the utility of affinity methods for characterizing structurally similar oligosaccharides.

Main Methods:

• Gas-liquid chromatography-mass spectrometry (GLC-MS) and direct probe mass spectrometry (MS) for structural analysis.
• Proton nuclear magnetic resonance (1H NMR) spectroscopy for detailed structural elucidation.
• Frontal analysis to determine binding affinities of oligosaccharides to monoclonal antibody 401/6.

Main Results:

• Three urinary oligosaccharides were identified: two heptasaccharides and one hexasaccharide, all containing alpha 1-4 and alpha 1-6 linkages.
• These oligosaccharides are limit dextrins resulting from alpha-amylase degradation of glycogen.
• Binding affinity to monoclonal antibody 401/6 correlated with the presence of specific non-reducing terminal sequences, with the tetrasaccharide Glc α 1-6Glc α 1-4Glc α 1-4Glc showing the highest affinity.

Conclusions:

• The identified oligosaccharides provide structural insights into glycogen degradation pathways in GSDs.
• Monoclonal antibody 401/6 specifically recognizes and binds to oligosaccharides with particular non-reducing terminal sequences.
• Affinity-based methods are effective for the isolation and characterization of structurally related oligosaccharides.