EFFECT OF HYDRATION AND PH ON THE THERMAL-STABILITY OF PROTEINASE-K

The effect of hydration and pH on the thermal stability of proteinase K was studied in the temperature range 310-450 K by differential scann ing calorimetry. The dependences of the denaturation temperature T-d, the specific enthalpy of denaturation Delta H-d and the maximum of exc ess apparent specific heat capacity (max)(ex) upon the degree of hydra tion h and the pH of the buffers used are presented. The relation betw een T-d and h is of the Flory-Garrett's type. By means of Ooi's model, the two components of the denaturation enthalpy arising from hydratio n and conformational change, respectively, were estimated. The fact th at the specific denaturation enthalpy of proteinase K is very low may be attributed to its very low enthalpy of conformational change per he avy atom.