Most of the characterised glycan phosphorylases are members of CAZy glycosyl hydrolase families,7 although it is unclear whether these phosphorylases evolved from hydrolases or vice
versa. Logic dictates there should be a hydrolase (or phosphorylase) for every sugar linkage in nature, barring any that are exclusively degraded by lyases. There are many more hydrolases
characterised than phosphorylases. If typically robust hydrolases could be engineered into phosphorylases, then the repertoire of glycosidic linkages that could be readily synthesised enzymatically from simple sugar phosphates would be enormous. In order to understand the similarities and differences between phosphorylases and hydrolases, detailed structural analysis of