3.5.4.3 | guanine + H2O = xanthine + NH3 |
catalytic mechanism, quantum mechanical calculations using multilayered ONIOM and molecular dynamics study, the active-site residues of the enzyme do not affect the tautomeric state of guanine, Glu55 and Asp114 play important roles in proton shuttling in the reaction, proton transfer from a Zn-bound water to protonate Asp114, which can then transfer its proton to the N3 of the bound guanine, facilitating the nucleophilic attack on C2 of the guanine by the Zn-bound hydroxide to form a tetrahedral intermediate. Glu55 then transfers a proton from the Zn-hydroxide to the amino group of the reaction intermediate, ammonia leaves the active site, and xanthine is freed by the cleavage of the Zn-O2 bond |
688614 |