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外文期刊>The biochemical journal
>Structural analysis of a glycoside hydrolase family 43 arabinoxylan arabinofuranohydrolase in complex with xylotetraose reveals a different binding mechanism compared with other members of the same family
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Structural analysis of a glycoside hydrolase family 43 arabinoxylan arabinofuranohydrolase in complex with xylotetraose reveals a different binding mechanism compared with other members of the same family
pAXHs (arabinoxylan arabinofuranohydrolases) are α-L-arabinofuranosidases that specifically hydrolyse the glycosidic bond between arabinofuranosyl substituents and xylopyranosyl backbone residues of arabinoxylan. iBacillus subtilis/i was recently shown to produce an AXH that cleaves arabinose units from O-2- or O-3-mono-substituted xylose residues: iBs/iAXH-m2,3 (iB. subtilis/i AXH-m2,3). Crystallographic analysis reveals a two-domain structure for this enzyme: a catalytic domain displaying a five-bladed β-propeller fold characteristic of GH (glycoside hydrolase) family 43 and a CBM (carbohydrate-binding module) with a β-sandwich fold belonging to CBM family 6. Binding of substrate to iBs/iAXH-m2,3 is largely based on hydrophobic stacking interactions, which probably allow the positional flexibility needed to hydrolyse both arabinose substituents at the O-2 or O-3 position of the xylose unit. Superposition of the iBs/iAXH-m2,3 structure with known structures of the GH family 43 exo-acting enzymes, β-xylosidase and α-L-arabinanase, each in complex with their substrate, reveals a different orientation of the sugar backbone./p
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