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Figure 5.
Figure 5. A schematic diagram showing the mechanism of
N-glycoside bond hydrolysis catalyzed by αMMC. Hydrogen bonding
at N3 and N1 by Arg163 and Ile71, respectively, facilitates the
cleavage of the glycoside bond (N9–C1′ ) and leads to the
formation of a transition state with oxycarbonium ion
development on the ribose. The oxycarbonium ion is then
stabilized by the negative charge of Glu160. The adenine ring
rotates by about 15° to the position found in the
adenine-bound structures to give enough space for the
OH^−of the nucleophile to bond to C1′. Meanwhile, movement
and conformational change of the ribose may occur because of the
release of the straining force after the N9–C1′ bond is
broken. A water molecule, OH0 or OH2, attacks the oxycarbonium
ion at C1′ and the proton is transferred to N9. Figure 5. A
schematic diagram showing the mechanism of N-glycoside bond
hydrolysis catalyzed by αMMC. Hydrogen bonding at N3 and N1 by
Arg163 and Ile71, respectively, facilitates the cleavage of the
glycoside bond (N9–C1′ ) and leads to the formation of a
transition state with oxycarbonium ion development on the
ribose. The oxycarbonium ion is then stabilized by the negative
charge of Glu160. The adenine ring rotates by about 15° to
the position found in the adenine-bound structures to give
enough space for the OH^−of the nucleophile to bond to
C1′. Meanwhile, movement and conformational change of the
ribose may occur because of the release of the straining force
after the N9–C1′ bond is broken. A water molecule, OH0 or
OH2, attacks the oxycarbonium ion at C1′ and the proton is
transferred to N9.
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