Structural and Biochemical Characterization of an Octameric Carbohydrate Acetylesterase from Sinorhizobium meliloti.

Carbohydrate acetylesterases, which have a highly specific role among plant-interacting bacterial species, remove the acetyl groups from plant carbohydrates. Here, we determined the crystal structure of Est24, an octameric carbohydrate acetylesterase from Sinorhizobium meliloti, at 1.45 Å resolution and investigated its biochemical properties. The structure of Est24 consisted of five parallel β strands flanked by α helices, which formed an octameric assembly with two distinct interfaces. The deacetylation activity of Est24 and its mutants around the substrate-binding pocket was investigated using several substrates, including glucose pentaacetate and acetyl alginate. Elucidation of the structure-function relationships of Est24 could provide valuable opportunities for biotechnological explorations.