Thermostability profiles of WT and the E265V/S267W, E265V/S267W/S61C-S115C, E265V/S267W/E190C-E238C, and M6 mutants. (A) Apparent melting temperatures of WT and the E265V/S267W, E265V/S267W/S61C-S115C, E265V/S267W/E190C-E238C, and M6 mutants determined by DSF, Tm represents the temperature at which 50% of the protein is unfolded. (B) Half-life at 45°C measured using C8 as a substrate at the respective optimal pH. (C) Half-life at 60°C measured using C8 as a substrate at the respective optimal pH.