E*d is directly related, through Eq. (4), to the activation enthalpy of denaturation (H*d), which is another important thermodynamic parameter expressing the total amount of energy required to denature the enzyme; therefore, large and positive values of E*d and H*d should be associated with high enzyme thermostability
[8,9]. The acid protease investigated here has a H*d value at 55 ◦C(311.39 kJ/mol) (Table 1) much higher than those of the abovementionedalkaline or neutral proteases from A. awamori [15], A.fumigatus [7] and N. alba [11], confirming the earlier conclusions.