Thermal Stability of Alpha-Amylases from Bacillus licheniformis andBacillus amyloliquefaciens: A Comparative Study

Differences in thermal stabilities of proteins are very common and determination of nature of non covalent interactions that contributes such differences is of immense importance in protein science. This study is an attempt to identify the intrinsic physico chemical factors that contributes toward stabilization of protein under various denaturing conditions. Alpha-Amylases from Bacillus licheniformis (BLA) and Bacillus amyloliquefaciens (BAA), significantly differing in their thermal stability, were use in this investigation. The thermal stabilities of both the enzymes were compared by using activity measurement, thermal unfolding and determination of transition temperature (Tm). Formation of salt bridge was found to be an important factor that confers stability to both the enzymes. The analysis of amino acid sequences of both the enzymes indicated that BLA has more hydrophobic score compared to BAA. Based on this study, it is suggested that the additional hydrophobicity of BLA intensifies hydrophobic interactions in the core region and form rigid and compact molecular structure.