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PDBsum entry 4j0c
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DOI no:
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J Mol Biol
425:2737-2751
(2013)
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PubMed id:
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Crystal structure of tannase from Lactobacillus plantarum.
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B.Ren,
M.Wu,
Q.Wang,
X.Peng,
H.Wen,
W.J.McKinstry,
Q.Chen.
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ABSTRACT
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Tannins are water-soluble polyphenolic compounds in plants. Hydrolyzable tannins
are derivatives of gallic acid (3,4,5-trihydroxybenzoic acid) or its
meta-depsidic forms that are esterified to polyol, catechin, or triterpenoid
units. Tannases are a family of esterases that catalyze the hydrolysis of the
galloyl ester bond in hydrolyzable tannins to release gallic acid. The enzymes
have found wide applications in food, feed, beverage, pharmaceutical, and
chemical industries since their discovery more than a century ago, although
little is known about them at the molecular level, including the details of the
catalytic and substrate binding sites. Here, we report the first
three-dimensional structure of a tannase from Lactobacillus plantarum. The
enzyme displays an α/β structure, featured by a large cap domain inserted into
the classical serine hydrolase fold. A catalytic triad was identified in the
structure, which is composed of Ser163, His451, and Asp419. During the binding
of gallic acid, the carboxyl group of the molecule forges hydrogen-bonding
interactions with the catalytic triad of the enzyme while the three hydroxyl
groups make contacts with Asp421, Lys343, and Glu357 to form another
hydrogen-bonding network. Mutagenesis studies demonstrated that these residues
are indispensable for the activity of the enzyme. Structural studies of the
enzyme in complex with a number of substrates indicated that the interactions at
the galloyl binding site are the determinant force for the binding of
substrates. The single galloyl binding site is responsible for the esterase and
depsidase activities of the enzyme.
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