ß-Mannosynthase: Synthesis of ß-Mannosides with a Mutant ß-Mannosidase.

Engineering enzymes: The glutamic acid nucleophile of a retaining ß-mannosidase has been replaced with a serine residue to form a ß-mannosynthase. When the new enzyme is provided with an α-mannosyl fluoride donor and an appropriate acceptor, ß-mannoside linkages are synthesized. Remarkably, α-mannosyl fluoride can be generated in situ by providing the mannosynthase with excess fluoride ion.