Download MendeleyStructural basis for broad substrate specificity in higher plant beta-D-glucan glucohydrolases.
Hrmova, M., De Gori, R., Smith, B.J., Fairweather, J.K., Driguez, H., Varghese, J.N., Fincher, G.B.(2002) Plant Cell 14: 1033-1052
- PubMed: 12034895
- DOI: https://doi.org/10.1105/tpc.010442
- Primary Citation of Related Structures:
1J8V - PubMed Abstract:
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.
Organizational Affiliation:
Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia.
