Comparison of lipases and glycoside hydrolases as catalysts in synthesis reactions.

Lipases and glycoside hydrolases have large similarities concerning reaction mechanisms. Acyl-enzyme intermediates are formed during lipase-catalyzed reactions and in an analogous way, retaining glycoside hydrolases form glycosyl-enzyme intermediates during catalysis. In both cases, the covalent enzyme intermediates can react with water or other nucleophiles containing hydroxyl groups. Simple alcohols are accepted as nucleophiles by both types of enzymes. Lipases are used very successfully in synthesis applications due to their efficiency in catalyzing reversed hydrolysis and transesterification reactions. On the other hand, synthesis applications of glycoside hydrolases are much less developed. Here, important similarities and differences between the enzyme groups are reviewed and approaches to reach high synthesis yields are discussed. Useful strategies include the use of low-water media, high nucleophile concentrations, as well as protein engineering to modify the selectivity of the enzymes. The transglycosylases, hydrolases which naturally catalyze mainly transfer reactions, are of special interest and might be useful guides for engineering of other hydrolases.