Fig. 6. Superposition of the structures of the native enzyme (green) with that of the Michaelis complex (yellow). Glu175 is located 3.0 Å from the glycosidic oxygen of Ara-α(1,3)-Xyl, which is a hydrogen-bonding distance, allowing the direct protonation of the departing aglycon. Glu294 is in an appropriate distance (3.2 Å) for a nucleophilic attack on the anomeric carbon.