抄録
The aim of our study is to synthesize various kinds of oligosaccharide units in glycoproteins or glycolipids by organic chemical methods and enzymatic methods for the elucidation of the function of carbohydrate chains. This paper focuses on the enzymatic synthesis of oligosaccharide components by the two types of reactions using glycosidases: reverse hydrolysis reactions and transglycosylation reactions. In reverse hydrolysis reactions, various linkages are formed so that the regioselectivity is usually low. On the other hand, in transglycosylation reactions using glycosidases, the regioselectivity is relatively high if the enzyme is properly selected. We have synthesized Manal-2Man, Manal-2Manal-2Man, G1cNAcβ1-2Man and GIcNAcf 1-6Man using the reverse hydrolysis activities of α-mannosidase and β-N-acetylglucosaminidase. We also synthesized regioselectively Galfl-4G1cNAcβ1-2Man and Galβ1-4G1cNAc/I1-6Man using the transglycosylation activities of β-galactosidases, Neu5Acα2-3Galβ1-4G1cNAc, Neu5Acα2-6Galβ1-4G1cNAc using sialidases, Fucal-2Gal, Fucal-3GIuNAc, Fucal-6GluNAc using α-fucosidases and Gal/il-3Glc and Galβ1-4G1c using the transglycosylation activities of β-galactanase. The proper use of reverse hydrolysis reaction and transglycosylation reaction turned out to be quite effective for the synthesis of oligosaccharides. These oligosaccharides can be used for the chemical synthesis of glycoconjugates.
