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Glycoside Hydrolase Family 39 β-Xylosidase of Sphingomonas Showing Salt/Ethanol/Trypsin Tolerance, Low-pH/Low-Temperature Activity, and Transxylosylation Activity

Li, Na, Han, Xiaowei, Xu, Shujing, Li, Chunyan, Wei, Xin, Liu, Yu, Zhang, Rui, Tang, Xianghua, Zhou, Junpei, Huang, Zunxi
Journal of agricultural and food chemistry 2018 v.66 no.36 pp. 9465-9472
Escherichia coli, Sphingomonas, amino acids, enzyme activity, ethanol, glycosides, microorganisms, moieties, pH, sodium chloride, sugars, trypsin, xylan 1,4-beta-xylosidase
Mining for novel enzymes from new microorganisms is a way to obtain β-xylosidases with promising applications. A Sphingomonas β-xylosidase was expressed in Escherichia coli. The purified recombinant enzyme (rJB13GH39) was most active at pH 4.5 and 50 °C, retaining 10%–50% of its maximum activity at 0–20 °C. Most salts and chemical reagents including 3.0%–20.0% (w/v) NaCl showed little or no effect on the enzymatic activity. rJB13GH39 exhibited 71.9% and 55.2% activity in 10.0% and 15.0% (v/v) ethanol, respectively. rJB13GH39 was stable below 60 °C in 3.0%–30.0% (w/v) NaCl, 3.0%–20.0% (v/v) ethanol, and 2.2–87.0 mg/mL trypsin. The enzyme transferred one xylosyl moiety to certain sugars and alcohols. The salt/ethanol tolerance and low-temperature activity of the enzyme may be attributed to its high structural flexibility caused by high proportions of small amino acids ACDGNSTV and random coils.