中国生物工程杂志

To improve the conversion efficiency of glucoside to small molecule compounds, the gene encoded β-glucosidase from Lactobacillus paracasei TK1501 was inserted into pET28a(+), and further transformed into E. coli BL21(DE3) for heterologous expression. The recombinant enzyme, which purified by nickel affinity chromatography, is conferred with the high specific activity of 675.56U/mg, and the molecular weight of 86.63kDa.The biochemical characterization of this recombinant enzyme shows that it exhibit the highest bio-activity in 30℃ and pH of 6.5, and the β-glucosidase activity was barely inhibited by Mg ²⁺ and Ca ²⁺, but largely by Cu ²⁺ with even no catalytic activity. It was also found that this enzyme possess a broad substrates specificity toward genistin, daidzin, daidzein, geniposide, salicin, heptosporin, polydatin and arbutin. Finally, The kinetics characteristics shows that K_m and V_max of this enzyme are 1.44mmol/L and 58.32mmol/(L·s), respectively, and the catalytic coefficient (k_cat) is 3 982/s using β-pNPG as the substrate. The all results above show that the β-Glucosidases from Lactobacillus paracasei TK1501 play important roles in the process of hydrolysis of soybean isoflavone and synthesis of glycosides.