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<p>Carbohydrate esterases modify polysaccharides by removing different ester moieties thereby affecting their physicochemical properties and their accessibility by glycoside hydrolases. We determined the full-length structures of two members (Fl8CE20_II and PpCE20_II) from the carbohydrate esterase family 20 (CE20) by X-ray crystallography that feature an ancillary domain, inserted into the catalytic SGNH-hydrolase domain. Detailed structural analysis identifies a so far undescribed catalytic triad architecture which lacks the typical aspartate for polarization of the histidine but instead reveals a precisely coordinated water molecule mediating contact between the His and Asp. This coordinated water in the Ser-His-(H<sub>2</sub>O-Asp/Asn) motif, as further confirmed by mutational studies and by&#xa0;determination of kinetic constants, is crucial for catalytic activity. We therefore term this active site architecture a water-mediated catalytic triad.</p>

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Insights into a water-mediated catalytic triad architecture in CE20 carbohydrate esterases

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月31日

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  • Michelle Teune,
  • Plínio S. Vieira,
  • Thorben Döhler,
  • Gottfried J. Palm,
  • Theresa Dutschei,
  • Daniel Bartosik,
  • Leona Berndt,
  • Gabriela F. Persinoti,
  • Sandra Maaß,
  • Dörte Becher,
  • Thomas Schweder,
  • Mário T. Murakami,
  • Michael Lammers,
  • Uwe T. Bornscheuer

摘要

Carbohydrate esterases modify polysaccharides by removing different ester moieties thereby affecting their physicochemical properties and their accessibility by glycoside hydrolases. We determined the full-length structures of two members (Fl8CE20_II and PpCE20_II) from the carbohydrate esterase family 20 (CE20) by X-ray crystallography that feature an ancillary domain, inserted into the catalytic SGNH-hydrolase domain. Detailed structural analysis identifies a so far undescribed catalytic triad architecture which lacks the typical aspartate for polarization of the histidine but instead reveals a precisely coordinated water molecule mediating contact between the His and Asp. This coordinated water in the Ser-His-(H2O-Asp/Asn) motif, as further confirmed by mutational studies and by determination of kinetic constants, is crucial for catalytic activity. We therefore term this active site architecture a water-mediated catalytic triad.