ENZYMATIC-SYNTHESIS OF 4-METHYLUMBELLIFERYL GLYCOSIDES OF TRISACCHARIDE AND CORE TETRASACCHARIDE, GAL(BETA-1-3)GAL(BETA-1-4)XYL AND GLCA(BETA-1-3)GAL(BETA-1-3)GAL(BETA-1-4)XYL, CORRESPONDING TO THE LINKAGE REGION OF PROTEOGLYCANS

Fluorescence labeled trisaccharide, Gal(beta 1-3)Gal(beta 1-4)Xyl(beta )-MU [MU = thyl-2-oxo-2H-chromen-7-yl(4-methylumbelliferyl)], and tetr asaccharide, GlcA(beta 1-3)Gal(beta 1-3)Gal(beta 1-4)Xyl(beta)-MU, cor responding to the linkage region between glycosaminoglycans and core p roteins in proteoglycans were synthesized from Xyl-MU by stepwise enzy matic transglycosidation using beta-galactosidase (Escherichia coil) a nd beta-glucuronidase (bovine liver). Introduction of the second galac tosyl residue at the 3'-position of Gal-Xyl-MU was achieved by minimal protection of the disaccharide intermediate whose reactive primary hy droxy function was selectively protected with an acetyl group by using lipase catalyzed transacetylation. Regioselective beta-glucuronylatio n was effected by the high substrate specificity of the beta-glucuroni dase without any protection of the glycosyl acceptor.