[Expression, purification and enzymatic characterization of Thermus thermophilus HB8 aspartate aminotransferase in Escherichia coli].

To obtain thermostable aspartate aminotransferase, the gene aspC from an extremely thermophilic bacterium, Thermus thermophilus HB8 was cloned, and its product was overexpressed in Escherichia coli BL21 (DE3) and Rosetta (DE3). The expression in Rosetta (DP3) was more efficient. The optimum reactive pH was 7, and the recombinant enzyme activity changed little when incubated in the buffer of pH8 - 10 on 37 degrees C for 1 h. The optimum reactive temprature was 75 degrees C, and the recombinant enzyme was more stable on the temperature of 25 - 55 degrees C. The half life of recombinant enzyme on 65 degrees C was 3.5 h, on 75 degrees C was 2.5 h. KmKG was 7.559 mmol/L, VmaxKG was 0.086 mmol/(L x min), KmAsp was 2.031 mmol/L, VmaxAsp was 0.024 mmol/(L x min). Ca2+, Fe3+, Mn2+ inhibited enzyme activity softly.