A highly thermostable mutant lipase was generated and characterized. Mutant enzyme demonstrated 144
fold enhanced thermostability over the wild type enzyme at 60 °C. Interestingly, the overall catalytic efficiency
(kcat/Km) of mutant was also enhanced (~20 folds). Circular dichroism spectroscopy, studied as function of
temperature, demonstrated that the mutant lipase retained its secondary structure up to 70–80 °C, whereas
wild type protein structure was completely distorted above 35 °C. Additionally, the intrinsic tryptophan fluorescence
(a probe for the tertiary structure) also displayed difference in the conformation of two enzymes
during temperature dependent unfolding. Furthermore, mutation N355K resulted in extensive H-bonding
(Lys355 HZ1OE2 Glu284) with a distance 2.44 Å. In contrast to this, Wt enzyme has not shown such Hbonding
interaction.