title: Molecular cloning and characterization of a novel β-glucosidase with high hydrolyzing ability for soybean isoflavone glycosides and glucose-tolerance from soil metagenomic library.
abstract: A novel β-glucosidase (Bgl1269) was identified from a metagenomic library of mangrove soil by activity-based functional screening. Sequence analysis revealed that Bgl1269 encodes a protein of 422 amino acids. After being overexpressed in Escherichia coli and purified, the enzymatic properties of Bgl1269 were investigated. The recombinant enzyme displayed a pH optimum of 6.0 and a temperature optimum of 40°C, and the addition of most common metal ions (1 or 10mM) increased the enzymatic activity evidently. In addition, the enzyme showed high hydrolyzing ability for soybean isoflavone glycosides, and 0.8unit of enzyme could completely converted daidzin and genistin (0.5mg/mL) to daidzein and genistein at 40°C for 0.5h. Interestingly, Bgl1269 also exhibited a very high glucose-tolerance, with the highest inhibition constant K(i) (4.28M) among β-glucosidases reported so far. These properties make it a good candidate in the production of soybean isoflavone aglycones after further study.
authors.affiliation: School of life science, Sun Yat-sen University, Guangzhou 510275, PR China.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xin-Jiong
authors.initials: XJ
authors.lastname: Fan
authors.forename: Yu-Huan
authors.initials: YH
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D055162:Biocatalysis / Q000187:drug effects; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability / Q000187:drug effects; D015723:Gene Library; D005947:Glucose / Q000494:pharmacology*; D005960:Glucosides / Q000378:metabolism; D006027:Glycosides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D006868:Hydrolysis / Q000187:drug effects; D007202:Indicators and Reagents; D007477:Ions; D007529:Isoflavones / Q000378:metabolism*; D007700:Kinetics; D054892:Metagenome / Q000187:drug effects*; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012988:Soil Microbiology; D013025:Glycine max / Q000737:chemistry*; D013696:Temperature; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics*
chemical_list: D005960:Glucosides; D006027:Glycosides; D007202:Indicators and Reagents; D007477:Ions; D007529:Isoflavones; D008670:Metals; D011994:Recombinant Proteins; C025193:4-nitrophenyl beta-D-glucoside; D001617:beta-Glucosidase; D005947:Glucose