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-gala ctopyranoside to a hydroxyl group of 2-acetamido-2-deoxy-galactopyrano se 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 solution s (20-60%). When beta-galactosidases from Penicillium multicolor and A spergillus oryzae were used as the catalysts, the beta(1-6)-linked dis accharide was produced as the major product. However, with beta-galact osidase from Bifidobacterium bifidum, the major products were the beta (1-4) and beta(1-6)-linked disaccha rides. On the other hand, with bet a-galactosidase from Streptococcus 6646K, beta(1-3)-linked disaccharid e 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 a lso synthesized with beta-galactosidase from S. 6646K and B. bifidum w ith 2-acetamido-2-deoxy-glucopyranose as the acceptor and PNPGal as th e donor. In both cases, the beta(1-4)-linked disaccharide was predomin antly produced. In addition, a comparative study was carried out to de termine the regioselectivity of the transglycosylation reaction as wel l as the hydrolytic specificity toward the same linked disaccharides. (C) 1996 Elsevier Science Ltd.