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Title
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Alternative strategy for converting an inverting glycoside hydrolase into a glycosynthase.
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Authors
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Y.Honda,
S.Fushinobu,
M.Hidaka,
T.Wakagi,
H.Shoun,
H.Taniguchi,
M.Kitaoka.
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Ref.
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Glycobiology, 2008,
18,
325-330.
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PubMed id
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Abstract
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The tyrosine residue Y198 is known to support a nucleophilic water molecule with
the general base residue, D263, in the reducing-end xylose-releasing
exo-oligoxylanase (Rex). A mutation in the tyrosine residue changing it into
phenylalanine caused a drastic decrease in the hydrolytic activity and a small
increase in the F(-) releasing activity from alpha-xylobiosyl fluoride in the
presence of xylose. In contrast, mutations at D263 resulted in the decreased
F(-) releasing activity. As a result of the high F(-) releasing activity and low
hydrolytic activity, Y198F of Rex accumulates a large amount of product during
the glycosynthase reaction. We propose a novel method for producing a
glycosynthase from an inverting glycoside hydrolase by mutating a residue that
holds the nucleophilic water molecule with the general base residue while
keeping the general base residue intact.
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