title: Comparison of three thermostable β-glucosidases for application in the hydrolysis of soybean isoflavone glycosides.
abstract: A novel thermostable β-glucosidase (Te-BglA) from Thermoanaerobacter ethanolicus JW200 was cloned, characterized and compared for its activity against isoflavone glycosides with two β-glucosidases (Tm-BglA, Tm-BglB) from Thermotoga maritima. Te-BglA exhibited maximum hydrolytic activity toward pNP-β-d-glucopyranoside (pNPG) at 80 °C and pH 7.0, was stable for a pH range of 4.6-7.8 and at 65 °C for 3 h, and had the lowest K(m) for the natural glycoside salicin and the highest relative substrate specificity (k(cat)/K(m))((salicin))/(k(cat)/K(m))((pNPG)) among the three enzymes. It converted isoflavone glycosides, including malonyl glycosides, in soybean flour to their aglycons more efficiently than Tm-BglA and Tm-BglB. After 3 h of incubation at 65 °C, Te-BglA produced complete hydrolysis of four isoflavone glycosides (namely, daidzin, genistin and their malonylated forms), exhibiting higher productivity of genistein and daidzein than the other two β-glucosidases. Our results suggest that Te-BglA is preferable to Tm-BglA and Tm-BglB, but all three enzymes have great potential applications in converting isoflavone glycosides into their aglycons.
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, College of Life Science, Nanjing Normal University, Nanjing, PR China 210046.
authors.forename: Xiangfei
authors.initials: X
authors.lastname: Song
authors.forename: Yemin
authors.initials: Y
authors.lastname: Xue
authors.forename: Qilei
authors.initials: Q
authors.lastname: Wang
authors.forename: Xixi
authors.initials: X
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D044602:Cellulases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D006027:Glycosides / Q000378:metabolism*; D006358:Hot Temperature; D006868:Hydrolysis; D007529:Isoflavones / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D011994:Recombinant Proteins; D017385:Sequence Homology; D013025:Glycine max / Q000737:chemistry*; D046968:Thermoanaerobacter / Q000201:enzymology*
chemical_list: D006027:Glycosides; D007529:Isoflavones; D011994:Recombinant Proteins; D044602:Cellulases