Substrate recognition by a bifunctional GH30-7 xylanase B from Talaromyces cellulolyticus

Area of Science:

• Enzymology
• Structural Biology
• Biochemistry

Background:

• Xylanase B from Talaromyces cellulolyticus (TcXyn30B) belongs to glycoside hydrolase family 30, subfamily 7.
• This enzyme possesses dual glucuronoxylanase and xylobiohydrolase activities.

Purpose of the Study:

• To determine the crystal structures of native TcXyn30B and its enzyme-product complex.
• To elucidate the structural basis for substrate recognition and catalytic mechanisms.

Main Methods:

• X-ray crystallography was used to determine the structures at 1.60 and 1.65 Å resolution.
• Site-directed mutagenesis was employed to investigate specific amino acid roles.

Main Results:

• The structure of the TcXyn30B-product complex revealed specific recognition of the glucuronyl side chain by conserved residues.
• Asn-93 was identified as a key residue interacting with the substrate, likely contributing to xylobiohydrolase activity.

Conclusions:

• The study provides detailed structural insights into the substrate recognition mechanisms of GH30-7 glucuronoxylanases.
• The findings clarify the roles of specific residues in the bifunctional activity of TcXyn30B.