Figure 4 - full size

Figure 4.
Proposed mechanisms of glucosyl transfer catalyzed by GT retaining enzymes. Two essential components of double-displacement, a catalytic nucleophile and a glucosyl-enzyme intermediate, are circled and framed, respectively. In S[n]i- and S[n]1-like mechanisms, the positively charged DGM (framed) is stabilized by the leaving group AMP-phosphate and the incoming nucleophile 4-hydroxyl group of the sugar.