21XQ

a novel GH8 family endoxylanase BgXyn8A

Summary for 21XQ

• Entry DOI: 10.2210/pdb21xq/pdb
• Related: 7D88
• Descriptor: Glycosyl hydrolase family 8 (1 entity in total)
• Functional Keywords: endoxylanase gh8, hydrolase
• Biological source: Bacillus glycinifermentans
• Total number of polymer chains: 1
• Total formula weight: 45101.08

Authors

Xie, W.,Liu, Y. (deposition date: 2026-01-03, release date: 2026-05-13, Last modification date: 2026-05-20)

Primary citation

Liu, Y.,Xie, W.,Zhang, Y.,Liang, S.,Wang, S.,Zhan, R.,Wang, C.,Wang, K.
Biochemical and structural characterization of a novel glycoside hydrolase family 8 endoxylanase with broad-spectrum xylooligosaccharide production.
Bioresour Technol, 454:134780-134780, 2026

PubMed Abstract: Glycoside hydrolase family 8 (GH8) xylanases exhibit substantial diversity in catalytic mode and product distribution, yet the structural basis underlying this functional divergence remains poorly understood. Here, we report the identification and characterization of BgXyn8A, a GH8 xylanase from Bacillus glycinifermentans that exhibits a distinct preference for endo-type cleavage. BgXyn8A hydrolyzes xylan and alkali-pretreated corncob into a broad spectrum of xylooligosaccharides (XOSs) with degrees of polymerization ranging from 2 to 10, without detectable xylose formation. Comparative structural analysis with the exo-biased homolog BiXyn8A demonstrated that differences in product specificity are not governed by catalytic residues but arise from non-catalytic structural features surrounding the substrate-binding cleft. Specifically, three β-sheet-rich peripheral regions form a rigid substrate-binding cleft that constrains substrate positioning and limits conformational flexibility, thereby favoring internal cleavage and early product release. In addition, a short entrance motif reduces stabilizing interactions with the substrate's reducing end, disfavoring iterative cleavage required for xylose formation. Consistently, transplantation of these features into BiXyn8A reprograms its product spectrum toward longer-chain XOSs while suppressing xylose production. This study extends the current structural understanding of GH8 xylanases and provides a foundation for the rational engineering of enzymes tailored for selective oligosaccharide production.

PubMed: 42086152
DOI: 10.1016/j.biortech.2026.134780

Experimental method

X-RAY DIFFRACTION (2.20002441176 Å)