The most generic GH engineering approach described to date is the so-called glycosynthase strategy . This involves the creation of a crippled enzyme, in which a catalytic carboxylate is replaced by a catalytically impotent moiety. The resulting mutant enzyme is fed with a strongly activated substrate that mimics the reaction intermediate (e.g. an α-glycosyl fluoride for a β-active wild-type (WT) enzyme), and turns the enzyme into an inverting glycosynthase. Albeit powerful, this method relies on the availability of a suitably reactive, but sufficiently stable substrate. Moreover, glycosynthases are intrinsically impotent biocatalysts that display extremely low activity, thus requiring large quantities of enzyme .