Biochemical and Structural Characterization of a Novel Bacterial Tannase From Lachnospiraceae bacterium in Ruminant Gastrointestinal Tract

Tannases are a family of esterases that catalyze the hydrolysis of ester and depside bonds present in hydrolyzable tannins to release gallic acid. Here, a novel tannase from Lachnospiraceae bacterium (TanA(Lb)) was characterized. The recombinant TanA(Lb) exhibited maximal activity at pH 7.0 and 50 degrees C, and it maintained more than 70% relative activity from 30 degrees C to 55 degrees C. The activity of TanA(Lb) was enhanced by Mg2+ and Ca2+, and was dramatically reduced by Cu2+ and Mn2+. TanA(Lb) is capable of degrading esters of phenolic acids with long-chain alcohols, such as lauryl gallate as well as tannic acid. The Km value and catalytic efficiency (k(cat) /Km) of TanA(Lb) toward five substrates showed that tannic acid (TA) was the favorite substrate. Homology modeling and structural analysis indicated that TanA(Lb) contains an insertion loop (residues 341-450). Based on the moleculer docking and molecular dynamics (MD) simulation, this loop was observed as a flap-like lid to interact with bulk substrates such as tannic acid. TanA(Lb) is a novel bacterial tannase, and the characteristics of this enzyme make it potentially interesting for industrial use.