Download MendeleyStructural and functional analysis of transglycosylation mechanism of glycogen branching enzyme from Vibrio vulnificus.
An, Y., Tran, P.L., Lee, S.J., Ahn, W.C., Park, K.H., Woo, E.J., Park, J.T.(2026) Int J Biol Macromol 343: 150415-150415
- PubMed: 41577281 Search on PubMed
- DOI: https://doi.org/10.1016/j.ijbiomac.2026.150415
- Primary Citation Related Structures:
9U77 - PubMed Abstract:
Glycogen branching enzymes (GBEs) catalyze the formation of α-1,6-glucosidic branches during glycogen biosynthesis. In this study, we characterized the GBE from Vibrio vulnificus (VvGBE), highlighting its distinct transglycosylation activity and capacity to generate short-chain branches from defined maltooligosaccharides. The VvGBE crystal structure revealed a typical (β/α) 8 -barrel fold comprising four domains (N1, N2, A, and C), characteristic of type I GBEs. Key residues, including Y229, F312, N389, D423, and E476, formed a negatively charged substrate-binding pocket, with N389 influencing branch length by favoring shorter chains. Biochemical assays showed that VvGBE preferentially transfers glucan chains with a peak degree of polymerization (DP) of 5. Structural superposition with the cceBE1 ligand model indicated that its binding pocket accommodates six glucose residues, with Y229 playing a role in determining the branching pattern. Substrate analysis revealed that a minimum DP of 11 is required for branch activity. Shorter substrates (< 11 glucose units) bound at the A1 site (M490, F489) for α-1,4-chain elongation, whereas longer substrates (≥11 units) adopt a U-shaped conformation at the A2 site (W644, V530) to form α-1,6-branches, with Y433 essential for proper acceptor positioning. These results refine our understanding of GBE substrate specificity and provide a structural framework for enzyme engineering.
- Jilin Medical University, Jilin, 132013, People's Republic of China.
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