[Purification and properties of thermostable catalase in engineered E. coli]

A thermostable catalase in engineered bacterium E. coli was purified to electrophoretic homogenenity by heat treatment, ammonium sulfate fractionation precipitation, DEAE-A50 ion exchange chromatography, HiPrep 16/10 Phenyl hydrophobic interaction chromatography and Superdex200 HR 10/30 size exclusion chromatography with 187.2-fold purification and 9.8% recovery. The optimum reaction temperature and pH of this recombinant catalase were 70 degrees C and 7.0 respectively. The catalase is stable below 60 degrees C and at pH range 3-8. The residual activity of the catalase was about 60% after treated at 70 degrees C for 60 minutes and 80 degrees C for 10 minutes. The apprant Km and Vmax value of the catalase were 7.75 mmol/L and 27.8 mmol.min-1.mg-1 respectively. The affects of some metal ions and compounds on this enzyme were shown. Zn2+, Ba2+, Mn2+ of 1 mmol/L could completely inactivate the enzyme, EDTA of 50 mmol/L had no affect on activity.