8IBK

Crystal structure of Bacillus sp. AHU2216 GH13_31 Alpha-glucosidase E256Q/N258G in complex with maltotriose

Summary for 8IBK

• Entry DOI: 10.2210/pdb8ibk/pdb
• Descriptor: Alpha-glucosidase, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: alpha-glucosidase, gh13_31, complex, alpha-amylase, hydrolase
• Biological source: Bacillus sp. (in: firmicutes)
• Total number of polymer chains: 1
• Total formula weight: 66527.16

Authors

Auiewiriyanukul, W.,Saburi, W.,Yu, J.,Kato, K.,Yao, M.,Mori, H. (deposition date: 2023-02-10, release date: 2023-05-03, Last modification date: 2024-05-29)

Primary citation

Auiewiriyanukul, W.,Saburi, W.,Ota, T.,Yu, J.,Kato, K.,Yao, M.,Mori, H.
Alteration of Substrate Specificity and Transglucosylation Activity of GH13_31 alpha-Glucosidase from Bacillus sp. AHU2216 through Site-Directed Mutagenesis of Asn258 on beta → alpha Loop 5.
Molecules, 28:-, 2023

PubMed Abstract: α-Glucosidase catalyzes the hydrolysis of α-d-glucosides and transglucosylation. sp. AHU2216 α-glucosidase (BspAG13_31A), belonging to the glycoside hydrolase family 13 subfamily 31, specifically cleaves α-(1→4)-glucosidic linkages and shows high disaccharide specificity. We showed previously that the maltose moiety of maltotriose (G3) and maltotetraose (G4), covering subsites +1 and +2 of BspAG13_31A, adopts a less stable conformation than the global minimum energy conformation. This unstable d-glucosyl conformation likely arises from steric hindrance by Asn258 on β→α loop 5 of the catalytic (β/α)-barrel. In this study, Asn258 mutants of BspAG13_31A were enzymatically and structurally analyzed. N258G/P mutations significantly enhanced trisaccharide specificity. The N258P mutation also enhanced the activity toward sucrose and produced erlose from sucrose through transglucosylation. N258G showed a higher specificity to transglucosylation with -nitrophenyl α-d-glucopyranoside and maltose than the wild type. E256Q/N258G and E258Q/N258P structures in complex with G3 revealed that the maltose moiety of G3 bound at subsites +1 and +2 adopted a relaxed conformation, whereas a less stable conformation was taken in E256Q. This structural difference suggests that stabilizing the G3 conformation enhances trisaccharide specificity. The E256Q/N258G-G3 complex formed an additional hydrogen bond between Met229 and the d-glucose residue of G3 in subsite +2, and this interaction may enhance transglucosylation.

PubMed: 37049872
DOI: 10.3390/molecules28073109

Experimental method

X-RAY DIFFRACTION (1.69 Å)