Abstract
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 (TanALb) was characterized. The recombinant TanALb exhibited maximal activity at pH 7.0 and 50°C, and it maintained more than 70% relative activity from 30°C to 55°C. The activity of TanALb was enhanced by Mg2+ and Ca2+, and was dramatically reduced by Cu2+ and Mn2+. TanALb 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 TanALb toward five substrates showed that tannic acid (TA) was the favorite substrate. Homology modeling and structural analysis indicated that TanALb 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. TanALb is a novel bacterial tannase, and the characteristics of this enzyme make it potentially interesting for industrial use.
Highlights
Tannins are water-soluble polyphenolic compounds that constitute the fourth most abundant class of plant biomass components, richly secreted by defensive systems in wood, fruits, roots, and seeds (White, 1957; Smeriglio et al, 2016; Maisetta et al, 2019)
A multiple sequence alignment was performed based on the protein sequence of tannase from Lachnospiraceae bacterium (TanALb) with characterized tannase from other organisms
The results showed that the root means square deviation (RMSD) of heavy atoms of TanALb was less than 10.0 Å, that of tannic acid was less than 5.0 Å, and the system achieved equilibrium within 150 ns (Supplementary Figure S6)
Summary
Tannins are water-soluble polyphenolic compounds that constitute the fourth most abundant class of plant biomass components, richly secreted by defensive systems in wood, fruits, roots, and seeds (White, 1957; Smeriglio et al, 2016; Maisetta et al, 2019). Tannins and their derivatives are the key compounds of the astringent taste of tea, fruits, and vegetables, and determine the quality of their production such as muddy and astringency problem of juice and beer (Charlton et al, 2002). There is an increasing demand for tannases with desirable biochemical properties in industry
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