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Type: Journal article
Title: Structural basis for broad substrate specificity in higher plant beta-D-glucan glucohydrolases
Author: Hrmova, M.
De Gori, R.
Smith, B.
Fairweather, J.
Driguez, H.
Varghese, J.
Fincher, G.
Citation: Plant Cell, 2002; 14(5):1033-1052
Publisher: Amer Soc Plant Physiologists
Issue Date: 2002
ISSN: 1040-4651
Statement of
Maria Hrmova, Ross De Gori, Brian J. Smith, Jon K. Fairweather, Hugues Driguez, Joseph N. Varghese, and Geoffrey B. Fincher
Abstract: Family 3 β-D-glucan glucohydrolases are distributed widely in higher plants. The enzymes catalyze the hydrolytic removal of β-D-glucosyl residues from nonreducing termini of a range of β-D-glucans and β-D-oligoglucosides. Their broad specificity can be explained by x-ray crystallographic data obtained from a barley β-D-glucan glucohydrolase in complex with nonhydrolyzable S-glycoside substrate analogs and by molecular modeling of enzyme/substrate complexes. The glucosyl residue that occupies binding subsite -1 is locked tightly into a fixed position through extensive hydrogen bonding with six amino acid residues near the bottom of an active site pocket. In contrast, the glucosyl residue at subsite +1 is located between two Trp residues at the entrance of the pocket, where it is constrained less tightly. The relative flexibility of binding at subsite +1, coupled with the projection of the remainder of bound substrate away from the enzyme's surface, means that the overall active site can accommodate a range of substrates with variable spatial dispositions of adjacent β-D-glucosyl residues. The broad specificity for glycosidic linkage type enables the enzyme to perform diverse functions during plant development.
Keywords: Plants; Glucans; Glycoside Hydrolases; Glucosidases; beta-Glucosidase; Glucan Endo-1,3-beta-D-Glucosidase; Cellobiose; Disaccharides; Trisaccharides; Phylogeny; Binding Sites; Amino Acid Sequence; Carbohydrate Sequence; Protein Binding; Sequence Homology, Amino Acid; Structure-Activity Relationship; Substrate Specificity; Kinetics; Catalysis; Models, Molecular; Molecular Sequence Data
RMID: 0020020858
DOI: 10.1105/tpc.010442
Appears in Collections:Agriculture, Food and Wine publications

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