The effect of high pressure on the change in the heat capacity (Delta c(p)) of ribonuclease A and lysozyme upon denaturation has been studied using scanning microcalorimetry techniques. It has been shown that the pressure has no impact on Delta c(p) up to 178 MPa, although appreciably varies the denaturation enthalpy. This result confirms the thermodynamic similarity of the denaturation process and the hydration degree of polypeptide chain in the denatured state at ambient and elevated pressure. Our findings are in conflict with some hypotheses concerning the high pressure effect on the structure stability of proteins. (C) 2015 Elsevier B.V. All rights reserved.