β‑Xylosidase in biocatalysis: from hydrolytic and transglycosylation mechanisms to protein engineering strategies
摘要
β-Xylosidase plays a crucial role in the degradation of xylan and hemicellulose, as well as the hydrolysis of various glycosides. This substrate diversity stems from family-specific structural adaptations: GH3 employs a conserved double-displacement mechanism with a unique pocket for efficient 7-xylosyl-10-deacetyltaxol (XDT) conversion; GH39 uses non-conserved hydrophobic residues to recognize saponin main chains; GH43 exhibits high variability in the β‑hairpin structures of its family members. Beyond hydrolysis, β-xylosidases achieve transglycosylation via a retention mechanism, forming covalent enzyme-xylose intermediates where receptor steric hindrance, polarity, and nucleophilicity determine reaction outcomes. Different families recognize carbohydrate, phenolic, and alcohol receptors through complementary active site topology, enabling green synthesis of alkyl xylosides and bioactive substances. Molecular engineering modifies β-xylosidases by introducing rigid elements, optimizing binding interfaces, and broadening substrate channels. This article reviews recent advances in hydrolysis and transglycosylation activities, explores catalytic mechanisms, and highlights breakthroughs in molecular modification strategies. It is intended to serve as a reference for future research and application of this enzyme family.
Graphical abstract