REGIOSELECTIVITY OF THE ENZYMATIC TRANSGALACTOSIDATION OF D-XYLOSE AND L-XYLOSE CATALYZED BY BETA-GALACTOSIDASES

The regioselectivity of enzymatic transgalactosidation depends on the source of the beta-galactosidase used. When the galactosyl acceptor on ly contains secondary hydroxyl groups, of anp of the three regioisomer s 4-, 3- and 2-O-beta-D-galactopyranosyl-D-xylose (1, 2 and 3, respect ively) or 4-, 3-and 2-O-beta-D-galactopyranosyl-L-xylose (4, 5 and 6, respectively). Enriched mixtures in 1, 2 or 3 were obtained using beta -galactosidases from Escherichia coli, bovine testes or Aspergillus or yzae, respectively, by transgalactosidation reaction of O-nitrophenyl- beta-D-galactopyranoside and D-xylose, and enriched mixtures in 4, 5 o r 6 were obtained in a similar way using beta-galactosidases from Aspe rgillus oryzae, lamb small-intestine (intestinal lactase-phloridzin hy drolase) or Saccharomyces fragilis, respectively, using L-xylose as ac ceptor. (C) 1998 Elsevier Science Ltd.