Characterization of a galactosynthase derived from Bacillus circulans β-galactosidase: facile synthesis of D-lacto- and D-galacto-N-bioside.
Glycosynthases-retaining glycosidases mutated at their catalytic nucleophile-catalyze the formation of glycosidic bonds from glycosyl fluorides as donor sugars and various glycosides as acceptor sugars. Here the first glycosynthase derived from a family 35 β-galactosidase is described. The Glu→Gly mutant of BgaC from Bacillus circulans (BgaC-E233G) catalyzed regioselective galactosylation at the 3-position of the sugar acceptors with α-galactosyl fluoride as the donor. Transfer to 4-nitophenyl α-D-N-acetyl-glucosaminide and α-D-N-acetylgalactosaminide yielded 4-nitophenyl α-lacto-N-biose and α-galacto-N-biose, respectively, in high yields (up to 98%). Kinetic analysis revealed that the high affinity of the acceptors contributed mostly to the BgaC-E233G-catalyzed transglycosylation. BgaC-E233G showed no activity with β-(1,3)-linked disaccharides as acceptors, thus suggesting that this enzyme can be used in "one-pot synthesis" of LNB- or GNB-containing glycans.
Department of Food and Biotechnology, Korea University, 2511 Sejong-ro, Sejong, 339-700 (Republic of Korea).
Chao
C
Li
Young-Wan
YW
Kim
D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D055162:Biocatalysis; D004187:Disaccharides / Q000096:biosynthesis* / Q000737:chemistry; D006031:Glycosylation; D007700:Kinetics; D013237:Stereoisomerism; D013379:Substrate Specificity; D001616:beta-Galactosidase / Q000378:metabolism*
D004187:Disaccharides; C056853:6-O-galactopyranosylgalactose; C033398:galactosyl-1,3-N-acetylglucosamine; C040456:lacto-N-biose II; D001616:beta-Galactosidase; D000117:Acetylglucosamine
beta-galactosidase; glycosylation; glycosynthase; regioselectivity; transglycosylation