Effects of Site-specific Mutagenesis of K253 and N184V on the Thermostability of D-Glucose Isomerase.

In order to enhance the thermostability of D-Glucose isomerase (GI), its mutants, GIK253R and GIN184V, were obtained with the double primer method of site-directed mutagenesis. Then their biochemical properties were assayed and compared with wild-type GI. The results showed that: (1) The mutant K253R was less stable than the wild-type GI at 70 degrees and 80 degrees. But in 1 M L-Rhaminose at 70 degrees, they had similar rate of heat inactivation. Furthermore, the mutant K253R has higher specific activity than the wild-type GI. (2) The mutant N184V had much less thermostability and specific activity as compared with the wild-type GI. These results were explained by their kinetic parameters and crystal structure model.