A novel -d-galactosynthase from Thermotoga maritima converts -d-galactopyranosyl azide to -galacto-oligosaccharides

Abstract

The large-scale production of oligosaccharides is a daunting task, hampering the study of the role of glycans in vivo and the testing of the efficacy of novel glycan-based drugs. Glycosynthases, mutated glycosidases that synthesize oligosaccharides in high yields, are becoming important chemo-enzymatic tools for the production of oligosaccharides. However, while β-glycosynthase can be produced with a rather well-established technology, examples of -glycosynthases are thus far limited only to enzymes from glycoside hydrolase 29 (GH29), GH31 and GH95 families. α-l-Fucosynthases from GH29 use convenient glycosyl azide derivatives as a strategic alternative to glycosyl fluoride donors. However, the general applicability of this method to other α-glycosynthases is not trivial and remains to be confirmed. Here, β-d-galactopyranosyl azide was converted to α-galacto- oligosaccharides with good yields and high regioselectivity, catalyzed by a novel -galactosynthase based on the GH36 α-galactosidase from the hyperthermophilic bacterium Thermotoga maritima. These results open a new avenue to the practical synthesis of biologically interesting α-galacto- oligosaccharides and demonstrate more widespread use of α-glycosylα- azide as donors, confirming their utility to expand the repertoire of glycosynthases. © 2011 The Author.