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Title: Functional and structural differences between isoflavonoid β-glycosidases from Dalbergia sp.
Authors: Phimonphan Chuankhayan
Thipwarin Rimlumduan
Waraporn Tantanuch
Narumol Mothong
Prachumporn T. Kongsaeree
Pornphimon Metheenukul
Jisnuson Svasti
Ole N. Jensen
James R Ketudat Cairns
Suranaree University of Technology
National Synchrotron Research Center, Thailand
Kasetsart University
Mahidol University
Syddansk Universitet
Keywords: Biochemistry, Genetics and Molecular Biology
Issue Date: 15-Dec-2007
Citation: Archives of Biochemistry and Biophysics. Vol.468, No.2 (2007), 205-216
Abstract: Among isoflavonoid β-glucosidases from Dalbergia species, that from Dalbergia nigrescens hydrolyzes isoflavonoid-7-O-β-d-apiosyl-1,6-β-d-glucosides more efficiently, while Dalbergia cochinchinensis β-glucosidase (dalcochinase) hydrolyzes its rotenoid glycoside substrate, dalcochinin β-d-glucoside (I), more efficiently. A cDNA encoding a glycosylated β-glucosidase with 81% identity with dalcochinase was cloned from D. nigrescens seeds, and its protein (Dnbglu2) expressed in Pichia pastoris. Purified Dnbglu2 hydrolyzed the D. nigrescens natural substrates dalpatein 7-O-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranoside (II) and dalnigrein 7-O-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranoside (III) at 400- and 5000-fold higher catalytic efficiency (kcat/Km) than I. Dalcochinase was mutated at two amino acid residues, A454S and E455G, that are homologous to previously described substrate binding residues and differ from the corresponding residues in Dnbglu2. The double mutant showed 4- and 6.8-fold increases in relative activity toward II and III, respectively. However, this activity was only 3% that of Dnbglu2 β-glucosidase, indicating other determinants are important for isoflavonoid diglycoside hydrolysis. © 2007 Elsevier Inc. All rights reserved.
ISSN: 10960384
Appears in Collections:Scopus 2006-2010

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