Study of the Regioselectivity in the Transglycosylation to D-Galactose Derivatives Using beta-Galactosidases of Various Origins

摘要

Although a recombinant beta-1,3-galactosidase from Bacillus circulans has been recognized to catalyze a regioselective transglycosylation to give beta-(1->3)-linked oligosaccharides,beta-D-Galp-(l->6)-D-Gal derivatives were recently reported to be synthesized predominantly when D-galactose derivatives were used as acceptors.In the present study,the relation between the regioselectivity in the transglycosylation reaction and the hydrolysis specificity of the beta-1,3-galactosidase was examined.Although beta-D-Galp-(l->3)-D-Ga1NAc was hy-drolyzed much faster than beta-D-Galp-(1->6)-D-GalNAc,beta-D-Galp-(1->3)-beta-D-Galp-OMe was hydrolyzed slower than beta-D-Galp-(l->6)-beta-D-Galp-OMe.This fact indicated preferential synthesis of beta-D-Galp-(l->6)-beta-D-Galp-OMe by transglycosylation.In the transglycosylation using other beta-galactosidases of different origins such as from B.circulans,bovine testes,and E.coli,moderate regioselectivity was observed in reactions using D-galactose as an acceptor.The unexpected regioselectivity in the transglycosylation to D-galactose was concluded to be a result only found in the reaction using the beta-1,3-galactosidase from Bacillus circulans,and could be attributed to irregular specificity in the hydrolysis reaction.