RETRACTED ARTICLE: Substrates specificity of tannase from Streptomyces sviceus and Lactobacillus plantarum

Dan Wang,Mingbo Wu,Yao Liu,Die Lv,Xueli Hu,Ye Zhao,Qiumei Zhong

doi:10.1186/s13568-018-0677-1

Abstract

Tannases can catalyze the hydrolysis of galloyl ester and depside bonds of hydrolysable tannins to release gallic acid and glucose, but tannases from different species have different substrate specificities. Our prior studies found that tannase from Lactobacillus plantarum (LP-tan) performed a higher esterase activity, while the tannase from Streptomyces sviceus (SS-tan) performed a higher depsidase activity; but the molecular mechanism is not elucidated. Based on the crystal structure of LP-tan and the amino acid sequences alignment between LP-tan and SS-tan, we found that the sandwich structure formed by Ile206-substrate-Pro356 in LP-tan was replaced with Ile253-substrate-Gly384 in SS-tan, and the flap domain (amino acids: 225–247) formed in LP-tan was missed in SS-tan, while a flap-like domain (amino acids: 93–143) was found in SS-tan. In this study, we investigated the functional role of sandwich structure and the flap (flap-like) domain in the substrate specificity of tannase. Site-directed mutagenesis was used to disrupt the sandwich structure in LP-tan (P356G) and rebuilt it in SS-tan (G384P). The flap in LP-tan and the flap-like domain in SS-tan were deleted to construct the new variants. The activity assay results showed that the sandwich and the flap domain can help to catalytic the ester bonds, while the flap-like domain in SS-tan mainly worked on the depside bonds. Enzymatic characterization and kinetics data showed that the sandwich and the flap domain can help to catalytic the ester bonds, while the flap-like domain in SS-tan may worked on the depside bonds.

Highlights

Tannins, the fourth abundant plant constituent, existing as water soluble, poly-phenolic compounds is widely distributed in plant kingdom, especially in roots, leaves, fruits, and seeds
In order to further investigate the substrate specificity of these two tannases, the amino acid sequences alignment between SS-tan and LP-tan were performed, the results only showed 35% sequence similarity, but all the substrate binding and catalytic triad were conserved
Based on the structure analysis of LP-tan, we found that the sandwich structure formed by Ile206Pro356 in LP-tan was replaced with Ile253-Gly384 in SStan, and the flap domain formed in LP-tan was missed in the SS-tan, while an additional flap-like sequence (93– 144) was found in the SS-tan

Summary

Introduction

The fourth abundant plant constituent, existing as water soluble, poly-phenolic compounds is widely distributed in plant kingdom, especially in roots, leaves, fruits, and seeds. Many microorganisms have developed the ability to grow in the presence of tannins through the induction of secreted enzymes that utilize these compounds as carbon and energy sources (Aguilar et al 2007). These enzymes are serine hydrolases, including tannin acyl hydrolases (EC 3.1.1.20), commonly referred as tannases. The production of secreted tannase for industrial applications involves the utility of either crude or semi-purified enzyme prepared from submerged or solid-state cultures of Aspergillus niger or Aspergillus oryzae fermented in the presence of tannic acid (Aguilar et al 2007; Varadharajan et al 2017; Wu et al 2018). Low yield and purity, batch variability and a poor understanding of catalytic mechanism of tannase

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