Characterization of an α‐L‐fucosidase in marine bacterium Wenyingzhuangia fucanilytica: new evidence on the catalytic sites of GH95 family glycosidases.

Background: α‐l‐Fucose confers unique functions for fucose‐containing biomolecules such as human milk oligosaccharides. α‐l‐Fucosidases can serve as desirable tools in the application of fucosylated saccharides. Discovering novel α‐l‐fucosidases and elucidating their enzyme properties are always worthy tasks. Results: A GH95 family α‐l‐fucosidase named Afc95A_Wf was cloned from the genome of the marine bacterium Wenyingzhuangia fucanilytica and expressed in Escherichia coli. It exhibited maximum activity at 40 °C and pH 7.5. Afc95A_Wf defined a different substrate specificity among reported α‐l‐fucosidases, which was capable of hydrolyzing α‐fucoside in CNP‐fucose, Fucα1‐2Galβ1‐4Glc and Galβ1‐4(Fucα1‐3)Glc, and showed a preference for α1,2‐fucosidic linkage. It adopted Asp residue in the amino acid sequence at position 391, which was distinct from the previously acknowledged residue of Asn. The predicted tertiary structure and site‐directed mutagenesis revealed that Asp391 participates in the catalysis of Afc95A_Wf. The differences in the substrate specificity and catalytic site shed light on that Afc95A_Wf adopted a novel mechanism in catalysis. Conclusion: A GH95 family α‐l‐fucosidase (Afc95A_Wf) was cloned and expressed. It showed a cleavage preference for α1,2‐fucosidic linkage to α1,3‐fucosidic linkage. Afc95A_Wf demonstrated a different substrate specificity and a residue at an important catalytic site compared with known GH95 family proteins, which revealed the occurrence of diversity on catalytic mechanisms in the GH95 family. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]