1. Academic Validation
  2. Crystal structure of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis

Crystal structure of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis

  • Acta Crystallogr F Struct Biol Commun. 2021 Nov 1;77(Pt 11):399-406. doi: 10.1107/S2053230X21009675.
Kohei Sasamoto 1 Tomoki Himiyama 2 Kunihiko Moriyoshi 3 Takashi Ohmoto 3 Koichi Uegaki 4 Yoshiaki Nishiya 1 Tsutomu Nakamura 2
Affiliations

Affiliations

  • 1 Division of Life Science, Graduate School of Science and Engineering, Setsunan University, 17-8 Ikeda-Nakamachi, Neyagawa, Osaka 572-8508, Japan.
  • 2 Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.
  • 3 Osaka Research Institute of Industrial Science and Technology, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan.
  • 4 Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
Abstract

The acetylxylan esterases (AXEs) classified into carbohydrate esterase family 4 (CE4) are metalloenzymes that catalyze the deacetylation of acetylated Carbohydrates. AXE from Caldanaerobacter subterraneus subsp. tengcongensis (TTE0866), which belongs to CE4, is composed of three parts: a signal sequence (residues 1-22), an N-terminal region (NTR; residues 23-135) and a catalytic domain (residues 136-324). TTE0866 catalyzes the deacetylation of highly substituted cellulose acetate and is expected to be useful for industrial applications in the reuse of resources. In this study, the crystal structure of TTE0866 (residues 23-324) was successfully determined. The crystal diffracted to 1.9 Å resolution and belonged to space group I212121. The catalytic domain (residues 136-321) exhibited a (β/α)7-barrel topology. However, electron density was not observed for the NTR (residues 23-135). The crystal packing revealed the presence of an intermolecular space without observable electron density, indicating that the NTR occupies this space without a defined conformation or was truncated during the crystallization process. Although the active-site conformation of TTE0866 was found to be highly similar to those of other CE4 Enzymes, the orientation of its Trp264 side chain near the active site was clearly distinct. The unique orientation of the Trp264 side chain formed a different-shaped cavity within TTE0866, which may contribute to its reactivity towards highly substituted cellulose acetate.

Keywords

Caldanaerobacter subterraneus subsp. tengcongensis; acetylxylan esterase; carbohydrate esterase family 4; cellulose acetate; crystal structure; thermophilic enzymes.

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