Hydrolysis of β-d-glucopyranosyl fluoride to α-d-glucose catalyzed by Aspergillus niger α-d-glucosidase

Edward J. Hehre, Hirokazu Matsui, Curtis F. Brewer

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Aspergillus niger α-d-glucosidase, crystallized and free of detectable activity for β-d-glucosides, catalyzes the slow hydrolysis of β-d-glucopyranosyl fluoride to form α-d-glucose. Maximal initial rates, V, for the hydrolysis of β-d-glucosyl fluoride, p-nitrophenyl α-d-glucopyranoside, and α-d-glucopyranosyl fluoride are 0.27, 0.75, and 78.5 μmol.min-1.mg-1, respectively, with corresponding V/K constants of 0.0068, 1.44, and 41.3. Independent lines of evidence make clear that the reaction stems from β-d-glucosyl fluoride and not from a contaminating trace of α-d-glucosyl fluoride, and is catalyzed by the α-d-glucosidase and not by an accompanying trace of β-d-glucosidase or glucoamylase. Maltotriose competitively inhibits the hydrolysis, and β-d-glucosyl fluoride in turn competitively inhibits the hydrolysis of p-nitrophenyl α-d-glucopyranoside, indicating that β-d-glucosyl fluoride is bound at the same site as known substrates for the α-glucosidase. Present findings provide new evidence that α-glucosidases are not restricted to α-d-glucosylic substrates or to reactions providing retention of configuration. They strongly support the concept that product configuration in glycosylase-catalyzed reactions is primarily determined by enzyme structures controlling the direction of approach of acceptor molecules to the reaction center rather than by the anomeric configuration of the substrate.

Original languageEnglish (US)
Pages (from-to)123-132
Number of pages10
JournalCarbohydrate Research
Volume198
Issue number1
DOIs
StatePublished - Apr 2 1990

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Organic Chemistry

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