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Characterization of a Galactosynthase Derived from Bacillus circulans β‐Galactosidase: Facile Synthesis of D ‐Lacto‐ and D ‐Galacto‐ N ‐bioside
Author(s) -
Li Chao,
Kim YoungWan
Publication year - 2014
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201300699
Subject(s) - bacillus circulans , chemistry , glycosidic bond , glycoside hydrolase , glycosyl donor , stereochemistry , nucleophile , regioselectivity , beta galactosidase , glycoside , glycan , enzyme , glycosyl , galactose , catalysis , biochemistry , escherichia coli , glycoprotein , gene
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.