Zhang Wenli, Zhang Tao, Jiang Bo, Mu Wanmeng
State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry and Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China.
Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, Jiangsu 214122, China.
J Sci Food Agric. 2016 Jan 15;96(1):49-56. doi: 10.1002/jsfa.7187. Epub 2015 Apr 23.
The rare sugar D-psicose is a hexoketose monosaccharide and a C-3 epimer of D-fructose. D-Psicose is a novel functional sweetener with 70% of the sweetness but only 0.3% of the energy content of sucrose. Generally, the industrial production of D-psicose involves a bioconversion from D-fructose induced by ketose 3-epimerases.
The D-psicose 3-epimerase (DPEase) gene from Treponema primitia ZAS-1 (Trpr-DPEase) was cloned and overexpressed in Escherichia coli BL21 (DE3). The recombinant enzyme was purified with a molecular mass of 33 kDa. Trpr-DPEase exhibited optimal activity at pH 8.0 and 70 °C and was sensitive to temperature, with relative thermal stability below 50 °C. It was strictly metal-dependent and displayed maximum catalytic activity with 450 µmol L(-1) Co(2+). The Km values of the enzyme for D-psicose and D-fructose were 209 and 279 mmol L(-1) respectively. The D-psicose/D-fructose equilibrium ratio of Trpr-DPEase was 28:72.
A novel DPEase from T. primitia ZAS-1 was characterized that could catalyze the formation of D-psicose from D-fructose. D-Psicose was produced at a yield of 137.5 g L(-1) from 500 g L(-1) D-fructose, suggesting that Trpr-DPEase might be appropriate for the industrial production of D-psicose.
稀有糖D-阿洛酮糖是一种己酮糖单糖，是D-果糖的C-3差向异构体。D-阿洛酮糖是一种新型功能性甜味剂，甜度为蔗糖的70%，但能量含量仅为蔗糖的0.3%。一般来说，D-阿洛酮糖的工业生产涉及由酮糖3-差向异构酶诱导的从D-果糖的生物转化。
克隆了来自原始密螺旋体ZAS-1（Trpr-DPEase）的D-阿洛酮糖3-差向异构酶（DPEase）基因，并在大肠杆菌BL21（DE3）中过表达。重组酶经纯化后分子量为33 kDa。Trpr-DPEase在pH 8.0和70℃时表现出最佳活性，对温度敏感，50℃以下相对热稳定性较低。它严格依赖金属，在450 μmol L(-1) Co(2+)存在下表现出最大催化活性。该酶对D-阿洛酮糖和D-果糖的Km值分别为209和279 mmol L(-1)。Trpr-DPEase的D-阿洛酮糖/D-果糖平衡比为28:72。
对来自原始密螺旋体ZAS-1的一种新型DPEase进行了表征，该酶可催化由D-果糖形成D-阿洛酮糖。以500 g L(-1) D-果糖为原料，D-阿洛酮糖的产量为137.5 g L(-1)，表明Trpr-DPEase可能适用于D-阿洛酮糖的工业生产。
