초록
<P>A novel thermostable β-glucosidase (Te-BglA) from <I>Thermoanaerobacter ethanolicus</I> JW200 was cloned, characterized and compared for its activity against isoflavone glycosides with two β-glucosidases (Tm-BglA, Tm-BglB) from <I>Thermotoga maritima</I>. Te-BglA exhibited maximum hydrolytic activity toward <I>p</I>NP-β-<SMALL>d</SMALL>-glucopyranoside (<I>p</I>NPG) 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 <I>K</I><SUB>m</SUB> for the natural glycoside salicin and the highest relative substrate specificity (<I>k</I><SUB>cat</SUB>/<I>K</I><SUB>m</SUB>)<SUP>(salicin)</SUP>/(<I>k</I><SUB>cat</SUB>/<I>K</I><SUB>m</SUB>)<SUP>(<I>p</I>NPG)</SUP> 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.</P>