Jiangsu Key Laboratory for Microbes and Functional Genomics, College of Life Science, Nanjing Normal University, Nanjing, PR China 210046.
J Agric Food Chem. 2011 Mar 9;59(5):1954-61. doi: 10.1021/jf1046915. Epub 2011 Feb 2.
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.
从嗜热厌氧菌 JW200 中克隆、鉴定并比较了一种新型耐热β-葡萄糖苷酶（Te-BglA），其活性与来自海栖热袍菌的两种β-葡萄糖苷酶（Tm-BglA、Tm-BglB）对异黄酮糖苷的活性进行了比较。Te-BglA 在 80°C 和 pH7.0 时对 pNP-β-d-吡喃葡萄糖苷（pNPG）表现出最大的水解活性，在 pH4.6-7.8 范围内稳定，在 65°C 下稳定 3 小时，对天然糖苷水杨苷的 K(m)最低，对三种酶中相对底物特异性（k(cat)/K(m))((水杨苷))/(k(cat)/K(m))((pNPG))最高。与 Tm-BglA 和 Tm-BglB 相比，它更有效地将大豆粉中的异黄酮糖苷（包括丙二酰化糖苷）转化为糖苷配基。在 65°C 孵育 3 小时后，Te-BglA 使四种异黄酮糖苷（大豆苷、染料木苷及其丙二酰化形式）完全水解，生成的染料木黄酮和大豆黄素的产率均高于另外两种β-葡萄糖苷酶。我们的研究结果表明，Te-BglA 优于 Tm-BglA 和 Tm-BglB，但这三种酶都具有将异黄酮糖苷转化为糖苷配基的巨大应用潜力。
