[Effect of Arg188Gln (G/A) mutation on enzymatic activity of kynureninase].

To verify whether the enzymatic activity of kynureninase (KYNU) could be changed by the Arg188Gln (G/A) mutation. The total RNA of human hepatic tissue was extracted and the gene cDNA was amplified by RT-PCR. Primers were designed according to the sequences around the site Arg188Gln of gene and the Arg188Gln (G/A) mutant cDNA was generated by site-directed mutagenesis. Both the wild-type and mutant-type genes were subcloned into pcDNA vectors and the recombinant plasmids were constructed. After being transfected into human embryonic kidney 293 (HEK293) cells, the expression of KYNU recombinant plasmids were assessed by Western blot. The enzymatic activities of KYNU were detected by high performance liquid chromatography (HPLC). The KYNU enzyme activities were expressed in both wild and mutant HEK293 cells. Michaelis constants (Km) of the wild and mutant KYNU were (9.833±0.513) μmol/L and (29.900±0.265) μmol/L, respectively (<0.05). The maximum velocities (Vmax) of the wild and mutant KYNU were (0.700±0.096) nmol·mg·min and (0.084±0.003) nmol·mg·min, respectively (<0.05). Arg188Gln (G/A) mutation can decrease the enzymatic activity of KYNU.