The synthesis of galactopyranosyl derivatives with beta-galactosidases of different origins

beta-Galactosidases from four different sources were used to catalyze the transfer of beta-D-galactopyranosyl from 4-nitrophenyl-beta-D-galactopyranoside to a hydroxyl group of 2-acetamido-2-deoxy-galactopyranose in the synthesis of Gal beta(1-3)GalNAc (1), Gal beta(1-4)GalNAc (2) and Gal beta(1-6)GalNAc (3), in triethyl phosphate buffered solutions (20-60%). When beta-galactosidases from Penicillium multicolor and Aspergillus oryzae were used as the catalysts, the beta(1-6)-linked disaccharide was produced as the major product. However, with beta-galactosidase from Bifidobacterium bifidum, the major products were the beta(1-4) and beta(1-6)-linked disaccha rides. On the other hand, with beta-galactosidase from Streptococcus 6646K, beta(1-3)-linked disaccharide was predominant together with beta(1-4)-linked isomer. Gal beta(1-3)GlcNAc (4), Gal beta(1-4)GlcNAc (5) and Gal beta(1-6)GlcNAc (6) were also synthesized with beta-galactosidase from S. 6646K and B. bifidum with 2-acetamido-2-deoxy-glucopyranose as the acceptor and PNPGal as the donor. In both cases, the beta(1-4)-linked disaccharide was predominantly produced. In addition, a comparative study was carried out to determine the regioselectivity of the transglycosylation reaction as well as the hydrolytic specificity toward the same linked disaccharides. (C) 1996 Elsevier Science Ltd.