9H4U

Deacetylase FI8 utilizes unconventional variant of a catalytic triad: the diluted triad

This is a non-PDB format compatible entry.

Summary for 9H4U

• Entry DOI: 10.2210/pdb9h4u/pdb
• Descriptor: Carbohydrate esterase FI8, TRIETHYLENE GLYCOL, DI(HYDROXYETHYL)ETHER, ... (6 entities in total)
• Functional Keywords: ce20 clan, deacetylase, hydrolase
• Biological source: Flavimarina sp. HEL_I_48
• Total number of polymer chains: 2
• Total formula weight: 146577.39

Authors

Palm, G.J.,Lammers, M. (deposition date: 2024-10-21, release date: 2025-08-27, Last modification date: 2025-09-03)

Primary citation

Teune, M.,Vieira, P.S.,Dohler, T.,Palm, G.J.,Dutschei, T.,Bartosik, D.,Berndt, L.,Persinoti, G.F.,Maass, S.,Becher, D.,Schweder, T.,Murakami, M.T.,Lammers, M.,Bornscheuer, U.T.
Insights into a water-mediated catalytic triad architecture in CE20 carbohydrate esterases.
Nat Commun, 16:7034-7034, 2025

PubMed Abstract: 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-(HO-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.

PubMed: 40745183
DOI: 10.1038/s41467-025-62387-5

Experimental method

X-RAY DIFFRACTION (1.541 Å)