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Publication Abstract from PubMed

Family 3 beta-D-glucan glucohydrolases are distributed widely in higher plants. The enzymes catalyze the hydrolytic removal of beta-D-glucosyl residues from nonreducing termini of a range of beta-D-glucans and beta-D-oligoglucosides. Their broad specificity can be explained by x-ray crystallographic data obtained from a barley beta-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 beta-D-glucosyl residues. The broad specificity for glycosidic linkage type enables the enzyme to perform diverse functions during plant development.

Structural basis for broad substrate specificity in higher plant beta-D-glucan glucohydrolases.,Hrmova M, De Gori R, Smith BJ, Fairweather JK, Driguez H, Varghese JN, Fincher GB Plant Cell. 2002 May;14(5):1033-52. PMID:12034895^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.