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Title: Substrate specificity in hydrolysis and transglucosylation by family 1 β-glucosidases from cassava and Thai rosewood
Authors: Prachumporn T. Kongsaeree
Khakhanang Ratananikom
Khuanjarat Choengpanya
Nusra Tongtubtim
Penporn Sujiwattanarat
Chompoonuth Porncharoennop
Amornrat Onpium
Jisnuson Svasti
Kasetsart University
Mahidol University
Keywords: Biochemistry, Genetics and Molecular Biology;Chemical Engineering
Issue Date: 1-Dec-2010
Citation: Journal of Molecular Catalysis B: Enzymatic. Vol.67, No.3-4 (2010), 257-265
Abstract: Thai rosewood (Dalbergia cochinchinensis Pierre) dalcochinase and cassava (Manihot esculenta Crantz) linamarase are glycoside hydrolase family 1 β-glucosidases with 47% amino acid sequence identity. Each enzyme can hydrolyze its natural substrate, dalcochinin-8′-O-β-d-glucoside and linamarin, respectively, but not the natural substrate of the other enzyme. Linamarase can transfer glucose to primary, secondary and tertiary alcohols with high efficiency, while dalcochinase can transglucosylate primary and secondary alcohols at moderate levels. In this study, eight amino acid residues in the aglycone binding pocket of dalcochinase were individually replaced with the corresponding residues of linamarase, in order to identify residues that may account for their catalytic differences. The residues I185 and V255 of dalcochinase appeared important for its substrate specificity, with their respective mutations resulting in 24- and 12-fold reductions in kcat/Kmfor the hydrolysis of dalcochinin-8′-O- β-d-glucoside. Transglucosylation activity was improved when I185, N189 and V255 of dalcochinase were replaced with A201, F205 and F271 of linamarase, respectively, suggesting these residues support transglucosylation in linamarase. Among these three mutants, only the N189F mutant showed significant increases in the rate constants for the reactivation of trapped glucosyl-enzyme intermediates by all alcohols. Together, our results suggest that both hydrophobicity and geometry are important determinants for substrate specificity in hydrolysis and transglucosylation by these family 1 β-glucosidases. © 2010 Elsevier B.V. All rights reserved.
ISSN: 13811177
Appears in Collections:Scopus 2006-2010

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