Acidic and proteolytic digestion of α-amylases from Bacillus licheniformis and Bacillus amyloliquefaciens: Stability and flexibility analysis

An investigation was carried out to compare the proteolytic resistance and acidic digestion of the mesophilic α-amylase from Bacillus amyloliquefaciens (BAA) and its thermophilic counterpart from Bacillus licheniformis (BLA). Correlation between sites of proteolytic cleavage and the three-dimensional structure of the α-amylases, with the application of theoretical modeling of BAA, allowed discussion of the flexibility and the stability of both enzymes. The thermophilic enzyme shows higher resistance to trypsin, papain and thermolysin but is sensitive to pronase and acidic digestion. Proteolytic digestion of the thermophilic enzyme leads to an increased activity of the enzyme at room temperature whereas results of SDS-PAGE indicate proteolytic cleavage. Furthermore, thermal stability and resistance to proteolysis for BLA and BAA in the presence of additives such as sorbitol, trehalose and glycerol were also investigated. In addition to thermal stabilization of the two enzymes, these additives also augmented the resistance of the enzymes to proteolysis.