Thermal denaturation of pepsin at acidic media: Using DSC, MALDI-TOF MS and PAGE techniques

• The “two independent two-state transitions model” was used for analyzing of thermal denaturation curves of pepsin.
• The results implicating the higher stability of pepsin at pH 4, are in good agreement with MALDI-TOF MS results.
• The corresponding maximum stabilities of pepsin, ΔG°(25), was obtained at pH 4 with values of 65. 3 kJ mol−1.

The thermal stability of pepsin in a strong acid medium as a function of pH has been investigated using differential scanning calorimetry (DSC), UV absorbance, polyacrylamide gel electrophoresis (PAGE) and MALDI-TOF MS methods. The “two independent two-state transitions model” with view of physiological function of pepsin was used for analyzing thermal denaturation curves. The transition temperature (Tm) values ranging from 305.15 to 319.15 K for the first transition and from 322.15 to 349.15 K for the second transition in the examined pH range implicating the higher stability at pH 4 are in good agreement with MALDI-TOF MS results. The corresponding maximum, ΔG°(25), was stability obtained at pH 4 with values of 65.3 kJ mol−1.