Expression and Characterization of Levansucrase from Clostridium acetobutylicum

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• 作者：Song Gao ; Xianghui Qi ; Darren J. Hart ; Herui Gao ; Yingfeng An
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2017
• 出版时间：February 1, 2017
• 年：2017
• 卷：65
• 期：4
• 页码：867-871
• 全文大小：355K
• ISSN：1520-5118

文摘

The Clostridium acetobutylicum gene Ca-SacB encoding levansucrase was cloned and expressed in Escherichia coli. Ca-SacB is composed of 1287 bp and encodes 428 amino acid residues, which could convert 150 mmol/L sucrose to levan with the liberation of glucose. The optimum pH and temperature of this enzyme for levan formation were pH 6 and 60 °C, respectively. Levansucrase activity of Ca-SacB was completely abolished by 5 mmol/L Ag⁺ and Hg²⁺. The K_m and V_max values for levansucrase were calculated to be 64 mmol/L and 190 μmol/min/mg, respectively. Interestingly, Ca-SacB was found to have high product specificity, and no fructooligosaccharide was identified in the product, indicating that Ca-SacB may be valuable for industrial production of levan. In addition, Ca-SacB is the first characterized levansucrase isolated from an anaerobic bacterium, which should be valuable for exploring new enzyme resources and deepening the understanding of the catalytic mechanisms of levansucrases.