Phosphorylases are highly versatile enzymes, which can readily be used to synthesise both simple glycosides and large, complex oligosaccharide chains. However, there are only a limited number of these enzymes currently known and re-engineering them to access novel glycan structures, whilst attractive, has limitations, with lower activity and often lower regiospecificity than wild type being observed to date.130 The likely diversity of activities already present in nature remains an attractive but untapped resource.