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https://hdl.handle.net/2440/13422
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Type: | Journal article |
Title: | Subsite affinities and disposition of catalytic amino acids in the substrate-binding region of barley 1,3-β-glucanases. Implications in plant-pathogen interactions |
Other Titles: | Subsite affinities and disposition of catalytic amino acids in the substrate-binding region of barley 1,3-beta-glucanases. Implications in plant-pathogen interactions |
Author: | Hrmova, M. Garrett, T. Fincher, G. |
Citation: | Journal of Biological Chemistry, 1995; 270(24):14556-14563 |
Publisher: | The American Society for Biochemistry and Molecular Biology, Inc. |
Issue Date: | 1995 |
ISSN: | 0021-9258 1083-351X |
Statement of Responsibility: | Maria Hrmova, Thomas P. J. Garrett and Geoffrey B. Fincher |
Abstract: | Oligo-1,3-β-glucosides with degrees of polymerization of 2-9 were labeled at their reducing terminal residues by catalytic tritiation. These substrates were used in detailed kinetic and thermodynamic analyses to examine substrate binding in 1,3-β-D-glucan glucanohydrolase (EC 3.2.1.39) isoenzymes GI, GII, and GIII from young seedlings of barley (Hordeum vulgare). Bond-cleavage frequencies, together with the kinetic parameter kcat/Km, have been calculated as a function of substrate chain length to define the number of subsites that accommodate individual β-glucosyl residues and to estimate binding energies at each subsite. Each isoenzyme has eight β-glucosyl-binding subsites. The catalytic amino acids are located between the third and fourth subsite from the nonreducing terminus of the substrate. Negative binding energies in subsites adjacent to the hydrolyzed glycosidic linkage suggest that some substrate distortion may occur in this region during binding and that the resultant strain induced in the substrate might facilitate hydrolytic cleavage. If the 1,3-β-glucanases exert their function as pathogenesis-related proteins by hydrolyzing the branched or substituted 1,3;1,6-β-glucans of fungal walls, it is clear that relatively extended regions of the cell wall polysaccharide must fit into the substrate-binding cleft of the enzyme. |
Keywords: | Hordeum beta-Glucosidase Glucan 1,3-beta-Glucosidase Amino Acids Substrate Specificity Hydrolysis Kinetics Catalysis Thermodynamics Models, Molecular |
Rights: | © 1995 by The American Society for Biochemistry and Molecular Biology, Inc. |
DOI: | 10.1074/jbc.270.24.14556 |
Published version: | http://dx.doi.org/10.1074/jbc.270.24.14556 |
Appears in Collections: | Agriculture, Food and Wine publications Aurora harvest 7 |
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