Characterization of a Thermostable Extracellular β-Glucosidase with Activities of Exoglucanase and Transglycosylation from Paecilomyces thermophila

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• 作者：Shaoqing Yang ; Zhengqiang Jiang ; Qiaojuan Yan ; Huifang Zhu
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2008
• 出版时间：January 23, 2008
• 年：2008
• 卷：56
• 期：2
• 页码：602 - 608
• 全文大小：689K
• 年卷期：v.56,no.2(January 23, 2008)
• ISSN：1520-5118

文摘

The purification and characterization of a novel extracellular β-glucosidase from Paecilomyces thermophila J18 was studied. The β-glucosidase was purified to 105-fold apparent homogeneity with a recovery yield of 21.7% by DEAE 52 and Sephacryl S-200 chromatographies. Its molecular masses were 116 and 197 kDa when detected by SDS-PAGE and gel filtration, respectively. It was a homodimeric glycoprotein with a carbohydrate content of 82.3%. The purified enzyme exhibited an optimal activity at 75 °C and pH 6.2. It was stable up to 65 °C and in the pH range of 5.0–8.5. The enzyme exhibited a broad substrate specificity and significantly hydrolyzed p-nitrophenyl-β-D-glucopyranoside (pNPG), cellobiose, gentiobiose, sophorose, amygdalin, salicin, daidzin, and genistin. Moreover, it displayed substantial activity on β-glucans such as laminarin and lichenan, indicating that the enzyme has some exoglucanase activity. The rate of glucose released by the purified enzyme from cellooligosaccharides with a degree of polymerization (DP ) ranging between 2 and 5 decreased with increasing chain length. Glucose and glucono-δ-lactone inhibited the β-glucosidase competitively with K_i values of 73 and 0.49 mM, respectively. The β-glucosidase hydrolyzed pNPG, cellobiose, gentiobiose, sophorose, salicin, and amygdalin, exhibiting apparent K_m values of 0.26, 0.65, 0.77, 1.06, 1.39, and 1.45 mM, respectively. Besides, the enzyme showed transglycosylation activity, producing oligosaccharides with higher DP than the substrates when cellooligosaccharides were hydrolyzed. These properties make this β-glucosidase useful for various biotechnological applications.