title: Biochemical characterization of a D-psicose 3-epimerase from Treponema primitia ZAS-1 and its application on enzymatic production of D-psicose.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry and Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China.
authors: Wenli
authors: W
authors: Zhang
authors: State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry and Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China.
authors: Tao
authors: T
authors: Zhang
authors: 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.
authors: Bo
authors: B
authors: Jiang
authors: 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.
authors: Wanmeng
authors: W
authors: Mu
mesh_terms: D003001:Cloning, Molecular; D002149:Energy Intake; D004926:Escherichia coli; D005524:Food Technology; D005632:Fructose / Q000096:biosynthesis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008670:Metals; D008970:Molecular Weight; D019998:Racemases and Epimerases / Q000737:chemistry* / Q000235:genetics; D013549:Sweetening Agents; D013696:Temperature; D014208:Treponema / Q000201:enzymology*
chemical_list: D008670:Metals; D013549:Sweetening Agents; C003243:psicose; D005632:Fructose; D019998:Racemases and Epimerases
keywords: characterization; d-psicose; d-psicose 3-epimerase; ketose 3-epimerase; rare sugar