TY - JOUR
T1 - A trapped covalent intermediate as a key catalytic element in the hydrolysis of a GH3 β-glucosidase
T2 - An X-ray crystallographic and biochemical study
AU - Hu, Chenxing
AU - Wang, Yibing
AU - Wang, Weiyang
AU - Cui, Wanli
AU - Jia, Xinyue
AU - Mayo, Kevin H.
AU - Zhou, Yifa
AU - Su, Jiyong
AU - Yuan, Ye
N1 - Publisher Copyright:
© 2024
PY - 2024/4
Y1 - 2024/4
N2 - Glycoside hydrolases (GHs) are industrially important enzymes that hydrolyze glycosidic bonds in glycoconjugates. In this study, we found a GH3 β-glucosidase (CcBgl3B) from Cellulosimicrobium cellulans sp. 21 was able to selectively hydrolyze the β-1,6-glucosidic bond linked glucose of ginsenosides. X-ray crystallographic studies of the ligand complex ginsenoside-specific β-glucosidase provided a novel finding that support the catalytic mechanism of GH3. The substrate was clearly identified within the catalytic center of wild-type CcBgl3B, revealing that the C1 atom of the glucose was covalently bound to the Oδ1 group of the conserved catalytic nucleophile Asp264 as an enzyme–glycosyl intermediate. The glycosylated Asp264 could be identified by mass spectrometry. Through site-directed mutagenesis studies with Asp264, it was found that the covalent intermediate state formed by Asp264 and the substrate was critical for catalysis. In addition, Glu525 variants (E525A, E525Q and E525D) showed no or marginal activity against pNPβGlc; thus, this residue could supply a proton for the reaction. Overall, our study provides an insight into the catalytic mechanism of the GH3 enzyme CcBgl3B.
AB - Glycoside hydrolases (GHs) are industrially important enzymes that hydrolyze glycosidic bonds in glycoconjugates. In this study, we found a GH3 β-glucosidase (CcBgl3B) from Cellulosimicrobium cellulans sp. 21 was able to selectively hydrolyze the β-1,6-glucosidic bond linked glucose of ginsenosides. X-ray crystallographic studies of the ligand complex ginsenoside-specific β-glucosidase provided a novel finding that support the catalytic mechanism of GH3. The substrate was clearly identified within the catalytic center of wild-type CcBgl3B, revealing that the C1 atom of the glucose was covalently bound to the Oδ1 group of the conserved catalytic nucleophile Asp264 as an enzyme–glycosyl intermediate. The glycosylated Asp264 could be identified by mass spectrometry. Through site-directed mutagenesis studies with Asp264, it was found that the covalent intermediate state formed by Asp264 and the substrate was critical for catalysis. In addition, Glu525 variants (E525A, E525Q and E525D) showed no or marginal activity against pNPβGlc; thus, this residue could supply a proton for the reaction. Overall, our study provides an insight into the catalytic mechanism of the GH3 enzyme CcBgl3B.
KW - Catalytic mechanism
KW - Crystal structure
KW - Glycoside hydrolase
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U2 - 10.1016/j.ijbiomac.2024.131131
DO - 10.1016/j.ijbiomac.2024.131131
M3 - Article
C2 - 38527679
AN - SCOPUS:85188951961
SN - 0141-8130
VL - 265
JO - International Journal of Biological Macromolecules
JF - International Journal of Biological Macromolecules
M1 - 131131
ER -