关键词: 北京棒杆菌, 天冬氨酸激酶, 酶学性质表征, 动力学

Abstract: By homologous sequence and protein structure analysis, we found that A380 was an absolutely conserved site of aspartate kinase, and performed the sitedirected mutagenesis, isolation, purification and characterization of the site. The results show that compared with the wild type (WT), the V_max of the mutant A380H is increased by 4.28 folds. The optimum temperature of the mutant A380H is increased from 28 ℃ to 35 ℃, the optimum pH  is still 7.5, and the halflife is shortened from 4.5 h to 3.5 h. The substrate inhibitors have inhibitory effects on WT and mutants, threonine and lysine show synergistic inhibition effects. However, threonine alone has an activation or inhibitory effect on A380H, Mg²⁺ and Ni²⁺have an activation effect on WT,  1,5 mmol/L of Cu²⁺ has an activation effect on A380H. Compared with WT, the inhibitory effect of methanol and isopropanol on A380H is enhanced. The inhibitory effect of nbutanol and acetonitrile on A380H is reduced and show activation.

Key words: Corynebacterium pekinense, aspartate kinase, kinetics, characterization of enzymatic property