title: Cloning and characterization of a new broadspecific β-glucosidase from Lactococcus sp. FSJ4.
abstract: A β-glucosidase gene bglX was cloned from Lactococcus sp. FSJ4 by the method of shotgun. The bglX open reading frame consisted of 1,437 bp, encoding 478 amino acids. SDS-PAGE showed a recombinant bglX monomer of 54 kDa. Substrate specificity study revealed that the enzyme exhibited multifunctional catalysis activity against pNPG, pNPX and pNPGal. This enzyme shows higher activity against aryl glycosides of xylose than those of glucose or galactose. The enzyme exhibited the maximal activity at 40 °C, and the optimal pH was 6.0 with pNPG and 6.5 with pNPX as the substrates. Molecular modeling and substrate docking showed that there should be one active center responsible for the mutifuntional activity in this enzyme, since the active site pocket was substantially wide to allow the entry of pNPG, pNPX and pNPGal, which elucidated the structure-function relationship in substrate specificities. Substrate docking results indicated that Glu180 and Glu377 were the essential catalytic residues of the enzyme. The CDOCKER_ENERGY values obtained by substrate docking indicated that the enzyme has higher activity against pNPX than those of pNPG and pNPGal. These observations are in conformity with the results obtained from experimental investigation. Therefore, such substrate specificity makes this β-glucosidase of great interest for further study on physiological and catalytic reaction processes.
authors.affiliation: State Key Laboratory Breeding Base for Sustainable Exploitation of Tropical Biotic Resources, Hainan University, Haikou, 570228, People's Republic of China.
authors.forename: Shujun
authors.initials: S
authors.lastname: Fang
authors.forename: Jie
authors.initials: J
authors.lastname: Chang
authors.forename: Yong Seok
authors.initials: YS
authors.lastname: Lee
authors.forename: Weiliang
authors.initials: W
authors.lastname: Guo
authors.forename: Yong Lark
authors.initials: YL
authors.lastname: Choi
authors.forename: Yongcan
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D020134:Catalytic Domain; D003001:Cloning, Molecular; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006027:Glycosides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D017045:Lactococcus / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D013696:Temperature; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D006027:Glycosides; D011994:Recombinant Proteins; D001617:beta-Glucosidase
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