Structural insights into curdlan degradation via a glycoside hydrolase containing a disruptive carbohydrate-binding module

• Published in: Biotechnology for biofuels 2024-03, Vol.17 (1), p.45-45, Article 45
• Main Authors: Lv, Tianhang, Feng, Juanjuan, Jia, Xiaoyu, Wang, Cheng, Li, Fudong, Peng, Hui, Xiao, Yazhong, Liu, Lin, He, Chao
• Format: Article
• Language: English
• Subjects: Binding; Carbohydrate-binding module; Carbohydrates; Chemical bonds; Chemical properties; Chemical research; Conformation; Crystal structure; Crystallography; Curdlan; Degradation; Endoglucanase; Enzymes; Geometry; Glucan; Glucans; Glycosidases; Glycoside hydrolase; Glycosides; Grooves; Hydrogen bonds; Hydrolases; Hydrolysis; Microbial polysaccharides; Modules; Molecular docking; Recognition; Substrate specificity; Substrates; Triple-helical β-1,3-glucan; β-1,3-Glucan; β-1,3-Glucanase
• ISSN: 2731-3654; 2731-3654; 1754-6834
• DOI: 10.1186/s13068-024-02494-5

Degradation via enzymatic processes for the production of valuable β-1,3-glucooligosaccharides (GOS) from curdlan has attracted considerable interest. CBM6E functions as a curdlan-specific β-1,3-endoglucanase, composed of a glycoside hydrolase family 128 (GH128) module and a carbohydrate-binding module (CBM) derived from family CBM6. Crystallographic analyses were conducted to comprehend the substrate specificity mechanism of CBM6E. This unveiled structures of both apo CBM6E and its GOS-complexed form. The GH128 and CBM6 modules constitute a cohesive unit, binding nine glucoside moieties within the catalytic groove in a singular helical conformation. By extending the substrate-binding groove, we engineered CBM6E variants with heightened hydrolytic activities, generating diverse GOS profiles from curdlan. Molecular docking, followed by mutation validation, unveiled the cooperative recognition of triple-helical β-1,3-glucan by the GH128 and CBM6 modules, along with the identification of a novel sugar-binding residue situated within the CBM6 module. Interestingly, supplementing the CBM6 module into curdlan gel disrupted the gel's network structure, enhancing the hydrolysis of curdlan by specific β-1,3-glucanases. This study offers new insights into the recognition mechanism of glycoside hydrolases toward triple-helical β-1,3-glucans, presenting an effective method to enhance endoglucanase activity and manipulate its product profile. Furthermore, it discovered a CBM module capable of disrupting the quaternary structures of curdlan, thereby boosting the hydrolytic activity of curdlan gel when co-incubated with β-1,3-glucanases. These findings hold relevance for developing future enzyme and CBM cocktails useful in GOS production from curdlan degradation.