Effect of hydration andpH on the thermal stability of proteinase K

The effect of hydration andpH on the thermal stability of proteinase K was studied in the temperature range 310–450 K by differential scanning calorimetry. The dependences of the denaturation temperatureT _d, the specific enthalpy of denaturation H _d and the maximum of excess apparent specific heat capacityC _ex ^max upon the degree of hydrationh and thepH of the buffers used are presented. The relation betweenT _d andh is of the Flory-Garrett's type. By means of Ooi's model, the two components of the denaturation enthalpy arising from hydration and conformational change, respectively, were estimated. The fact that the specific denaturation enthalpy of proteinase K is very low may be attributed to its very low enthalpy of conformational change per heavy atom.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthdayThis major project was supported by the National Natural Science Foundation of China.