Improvement of thermostability and halostability of β-1,3-1,4-glucanase by substituting hydrophobic residue for Lys48

- The β-1,3-1,4-glucanase was increased thermostability and halostability by substituting hydrophobic residue for Lys48.
- The half-lives of K48A and K48L, were significantly increased more than 3-fold in thermal and high salinity conditions.
- The mutant enzymes were more active and stable than their wild-type in ionic liquids.

The aim of this study was to improve the stability of β-1,3-1,4-glucanase by substituting hydrophobic residue for specific amino acid. The results indicated that the catalytic efficiency, thermostability and halostability were enhanced simultaneously by replacement of Lys48 with Ala (K48A) or Leu (K48L). Comparison of kinetic parameters revealed that catalytic efficiency of mutants is enhanced as a result of the increase in substrate affinity. A great improvement in thermostability and halostability was observed. The half-lives of mutants significantly increased (up to ∼7-fold) at 60-70 °C. Moreover, relative enzymatic activities of mutants were observed more than 80% even in the presence of 30% NaCl, and half-lives were increased to 3-fold that of wild-type. Based on above results, when applied to ionic liquid, mutants were more active and stable compared to wild-type. These were the results from improvement of protein functions by the substitution of hydrophobic single residue in adjacent with forming carbohydrate binding cavity. Therefore, this report could be helpful for improvement of the enzyme property and for biotechnological application as well.