Gao Song, Qi Xianghui, Hart Darren J, Gao Herui, An Yingfeng
School of Food and Biological Engineering, Jiangsu University , Zhenjiang 212000, China.
Institut de Biologie Structurale (IBS), CEA, CNRS, University Grenoble Alpes , Grenoble 38044, France.
J Agric Food Chem. 2017 Feb 1;65(4):867-871. doi: 10.1021/acs.jafc.6b05165. Epub 2017 Jan 18.
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 Hg. The K and V 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.
编码果聚糖蔗糖酶的丙酮丁醇梭菌基因Ca-SacB在大肠杆菌中被克隆并表达。Ca-SacB由1287个碱基对组成，编码428个氨基酸残基，它能将150 mmol/L的蔗糖转化为果聚糖并释放出葡萄糖。该酶形成果聚糖的最适pH和温度分别为pH 6和60℃。5 mmol/L的银和汞能完全消除Ca-SacB的果聚糖蔗糖酶活性。果聚糖蔗糖酶的K值和V值经计算分别为64 mmol/L和190 μmol/min/mg。有趣的是，发现Ca-SacB具有较高的产物特异性，产物中未鉴定出低聚果糖，这表明Ca-SacB可能对果聚糖的工业生产具有重要价值。此外，Ca-SacB是从厌氧菌中分离得到的首个被表征的果聚糖蔗糖酶，这对于探索新的酶资源以及加深对果聚糖蔗糖酶催化机制的理解具有重要意义。
