Polysaccharides from seeds of Strychnos species

The chemical composition of polysaccharide fractions from Strychnos nux-vomica and S. innocua seeds and comparison with those from S. potatorum seeds are reported. The structural features of the galactomannans from the three Strychnos species are also discussed. © 1995

Polysaccharides from seeds of Strychnos species

The chemical composition of polysaccharide fractions from Strychnos nux-vomica and S. innocua seeds and comparison with those from S. potatorum seeds are reported. The structural features of the galactomannans from the three Strychnos species are also discussed. © 1995

A novel alpha-D-galactosynthase from Thermotoga maritima converts beta-D-galactopyranosyl azide to alpha-galacto-oligosaccharides

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 beta-glycosynthase can be produced with a rather well-established technology, examples of alpha-glycosynthases are thus far limited only to enzymes from glycoside hydrolase 29 (GH29), GH31 and GH95 families. alpha-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 alpha-glycosynthases is not trivial and remains to be confirmed. Here, beta-d-galactopyranosyl azide was converted to alpha-galacto-oligosaccharides with good yields and high regioselectivity, catalyzed by a novel alpha-galactosynthase based on the GH36 alpha-galactosidase from the hyperthermophilic bacterium Thermotoga maritima. These results open a new avenue to the practical synthesis of biologically interesting alpha-galacto-oligosaccharides and demonstrate more widespread use of beta-glycosyl-azide as donors, confirming their utility to expand the repertoire of glycosynthase

Beta-glycosyl azides as substrates for alpha-glycosynthases: preparation of efficient alpha-L-fucosynthases

Fucose-containing oligosaccharides play a central role in physio-pathological events, and fucosylated oligosaccharides have interesting potential applications in biomedicine. No methods for the large-scale production of oligosaccharides are currently available, but the chemo-enzymatic approach is very promising. Glycosynthases, mutated glycosidases that synthesize oligosaccharides in high yields, have been demonstrated to be an interesting alternative. However, examples of glycosynthases available so far are restricted to a limited number of glycosidases families and to only one retaining alpha-glycosynthase. We show here that new mutants of two alpha-L-fucosidases are efficient alpha-L-fucosynthases. The approach shown utilized beta-L-fucopyranosyl azide as donor substrate leading to transglycosylation yields up to 91%. This is the first method exploiting a beta-glycosylazide donor for alpha-glycosynthases; its applicability to the glycosynthetic methodology in a wider perspective is presente