FIG 6.

Analysis results of Dac and its mutants. (a) The specific activities of the R157 mutants. (b) SDS-PAGE analysis of the purified Dac. M, protein marker; 1, culture supernatant of recombinant strain WB-NMKmut/Dac after fermentation for 60 h; 2, culture supernatant was heated at 85°C for 30 min; 3, Dac purified by using an anion-exchange chromatography column. (c) Calculation of kinetic parameters of Dac and its mutants according to Lineweaver-Burk plot. To test the specific activity and kinetic parameters of the R157 mutants, the experiments were performed using the purified enzymes at 40°C and pH 8.0. Error bars indicate the average values from three parallel experiments.