Broadening the synthetic potential of disaccharide phosphorylases through enzyme engineering

In recent years, disaccharide phosphorylases have attracted increasing attention as promising biocatalysts for the production of glycosylated compounds. These enzymes make use of a glycosyl phosphate as donor substrate, which is much cheaper than the nucleotide-activated donors required by glycosyl transferases. Unfortunately, the number of available donor specificities is rather limited, and typically only allow the transfer of either a glucosyl or a galactosyl residue. In addition, most phosphorylases have a strong preference for carbohydrate acceptors, and can thus only be used for the synthesis of saccharide chains. The engineering of their substrate specificity thus is of significant value to broaden the range of products that can be obtained. Furthermore, the stability of some phosphorylases will also need to be improved to allow their commercial exploitation in a variety of industrial processes. In this review, several strategies for the engineering of these parameters are discussed and illustrated with some recent successes.