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Glycosynthases are mutant glycosidases, which in the presence of activated glycosides and suitable reaction conditions, synthesize oligosaccharides without hydrolysing them. This feature makes these catalysts promising tools for the large scale synthesis of carbohydrates. However, despite the popularity of the glycosynthetic approach, the number of enzymes effecting glycosynthetic reactions is still limited. We report here on the design of novel reaction conditions for a thermophilic α-l-fucosidase mutant, which might provide a route for the production of novel glycosynthases.

Carbohydrates serve as structural components and en- ergy sources of cells. More interestingly, however, these biomolecules are involved in a variety of molecular recognition processes in intercellular communication and signal transduction such as cell adhesion, differ- entiation, development and regulation. For these rea- sons, great interest has arisen in carbohydrate-based pharmaceuticals and on the development of techniques for the analysis and synthesis of oligosaccharides. In this respect, enzymes involved in carbohydrates hydrolysis and modification are increasingly being utilised for the bioconversion of sugars, for the synthesis of oligosac- charides with potential application, and for the charac- terisation of carbohydrate compounds of unknown structure. In this review, the enzymology and the applications of three glycosyl hydrolases from the archaeon Sulfolobus solfataricus are described. In particular, we focus on the enzymological properties of a b-glycosidase, an a-xylo- sidase, and an a-fucosidase; their exploitation in oligo- saccharides synthesis will be also described.