The Use of Enzymes for Structural Determination of Complex Carbohydrates
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It has been shown that sugar units in glycoconjugates carry specific biological messages. They have been found to serve as blood group determinants, cell surface antigens, and receptors for hormones, toxins and viruses. In order to understand the biological activity of a glycoconjugate, it is very important to accurately determine the structure of its complex carbohydrate chains. A complete structural analysis of a complex carbohydrate chain includes the determination of the anomeric configuration of each sugar unit, the sequential arrangement of sugar moieties and the linkage-points between pairs of monosaccharides within the sugar chain. Among the chemical methods, periodate oxidation and permethylation analysis are very useful, however, these two methods cannot provide information about the anomeric configuration and sequential arrangement of sugar units. We have shown that the stepwise release of monosaccharide units from the non-reducing terminus of a sugar chain by specific exo-glycosidases can provide us with this information. The use of endo-glycosidases to cleave the endoglycosidic linkages of a sugar chain has also been useful. The use of glycosidases for the structural analysis of complex carbohydrates is analogous to that of using nucleases and proteases for the structural analyses of nucleic acids and proteins, respectively. Since no single method can furnish complete structural information of a sugar chain, it is advantageous to use glycosidases together with other methods such as permethylation analysis and NMR spectroscopy to study the primary structure of complex carbohydrates.
KeywordsComplex Carbohydrate Sugar Chain Sugar Unit Jack Bean Bovine Erythrocyte
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