Purification and Characterization of Amylomaltase from Genetic Engineer Strain E.coli BL21/pET-DsbA-MalQ

The fusion protein was purified by Ni-NTA His-Bind affinity chromatography and cut with thrombin. The purified protein had 4-α-glucanotransferase activities. Its optimum pH and optimum temperature were 37 ℃ and pH 6.5, respectively. When the enzyme was treated at different temperature or pH, the enzyme activity would show different. When the treated temperature was over 40 ℃ or the treated pH below 4.5 or over 9.0, the enzyme activity would decrease quickly. Influences of ions and EDTA on enzyme activity were studied. The results showed that ions Zn2+, Cu2+, Hg2+, Ag+ inhibited enzyme activity, ion Ca2+, Mg2+, Mn2+ increased the enzyme activity, while EDTA showed no such effects on the enzymes. The Km and Vmax were 0.378 mmol/L and 1.979 mmol/(L·min), respectively.