Xue Yemin, Yu Jinjin, Song Xiangfei
Nanjing Engineering and Technology Research Center for Microbiology, Jiangsu Key Laboratory for Biodiversity and Biotechnology, Nanjing Normal University, Nanjing, People's Republic of China.
J Ind Microbiol Biotechnol. 2009 Nov;36(11):1401-8. doi: 10.1007/s10295-009-0626-8. Epub 2009 Aug 20.
A recombinant Thermotoga maritima beta-glucosidase A (BglA) was purified to homogeneity for performing enzymatic hydrolysis of isoflavone glycosides from soy flour. The kinetic properties K(m), k(cat), and k(cat)/K(m) of BglA towards isoflavone glycosides, determined using high-performance liquid chromatography, confirmed the higher efficiency of BglA in hydrolyzing malonylglycosides than non-conjugated glycosides (daidzin and genistin). During hydrolysis of soy flour by BglA at 80 degrees C, the isoflavone glycosides (soluble form) were extracted from soy flour (solid state) into the solution (liquid state) in thermal condition and converted to their aglycones (insoluble form), which mostly existed in the pellet to be separated from BglA in the reaction solution. The enzymatic hydrolysis in one-step and two-step approaches yielded 0.38 and 0.35 mg genistein and daidzein per gram of soy flour, respectively. The optimum conditions for conversion of isoflavone aglycones were 100 U per gram of soy flour, substrate concentration 25% (w/v), and incubation time 3 h for 80 degrees C.
纯化了重组嗜热栖热菌β-葡萄糖苷酶A（BglA），使其达到同质状态，用于对大豆粉中的异黄酮糖苷进行酶促水解。使用高效液相色谱法测定了BglA对异黄酮糖苷的动力学性质K(m)、k(cat)和k(cat)/K(m)，证实了BglA水解丙二酰糖苷的效率高于非共轭糖苷（大豆苷和染料木苷）。在80℃下用BglA水解大豆粉时，异黄酮糖苷（可溶形式）在热条件下从大豆粉（固态）中提取到溶液（液态）中，并转化为其苷元（不溶形式），苷元大多存在于沉淀中，以便与反应溶液中的BglA分离。一步法和两步法酶促水解每克大豆粉分别产生0.38毫克染料木素和大豆苷元以及0.35毫克大豆苷元和染料木素。异黄酮苷元转化的最佳条件是每克大豆粉100 U、底物浓度25%（w/v）以及在80℃下孵育3小时。
