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Figure 7.
FIGURE 7. Active site interactions and catalysis in family
CE4 acetylxylan esterases. Schematic diagram of the metal ion
coordination of the S. lividans family CE4 esterase (acetate
shown in red)(A) and the C. thermocellum CE4 esterase (B) and a
putative reaction mechanism (C) based upon classical Zn^2+
hydrolase chemistry and the work of van Aalten and colleagues
(19) on the streptococcal peptidoglycan deacetylases. The
divalent metal plays the role of Lewis acid, with Asp and His
residues playing the roles of catalytic base (activating the
nucleophilic water) and acid (aiding sugar departure).
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