Figure 3.

Complete structural mechanism of sucrose hydrolysis by BmSUH. A, conformational changes in the active site during sucrose hydrolysis. E, enzyme; S, substrate; I, covalent intermediate; P₁, product fructose; P₂, product glucose; A/B, acid/base catalyst; Nuc, nucleophilic catalyst. The amino acid residues of E (white), E·S (pink), E-I·P₁ (cyan), E-I (green), and E·P₂ (yellow) states are indicated as sticks and their ligands as thin sticks. The distance between an oxygen atom of Asp²⁴⁷ nucleophilic catalyst and C1 atom of the glucose residue of substrate in the Michaelis (E·S) complex is shown as a green dashed line. The stick models of amino acid residues in a preceding state are superposed for transparency, and arrows indicate conformational changes of the residues. B, conformational itinerary of glucose during BmSUH hydrolytic reaction.