Thermodynamic analysis of Bacillus cereus oligo-1,6-glucosidase and its cumulatively proline-introduced mutant proteins by differential scanning calorimetry

Differential scanning calorimetry (DSC) was used to characterize thermodynamically the stability of Bacillus cereus ATCC7064 oligo-1,6-glucosidase (dextrin 6-α-d-glucanohydrolase, EC 3.2.1.10) and its proline-introduced mutants. DSC analysis revealed that the free energy change of unfolding for the mutants cumulatively increased as the number of introduced proline residues increased. The resulting increase in the free energy change was ascribed to the concomitant decrease in the entropy change of polypeptide backbone unfolding in the mutants.