The thermal denaturation of hydrated rabbit muscle aldolase was studied by DSC in the water content range 0.08-2.28 g water/g protein. At a water content of 0.08 g/g, 2 endothermic peaks were seen on the thermogram. The peak in the lower temperature region was very small and the peak in the higher temperature region was very large. With increasing water contents, the small peak became smaller and the large peak began to split into 2. At a water content of 0.22 g/g, the small peak disappeared and the large peak split into 2 independent peaks. With a further increase in water content, the front peak of the 2 peaks moved to low temperature, and continued until the water content was equal to 0.65 g/g. The other peak remained unchanged. The enthalpies of the 2 peaks changed with increase in water content. The small peak apparently resulted from melting of crystals of hydrated aldolase and the other 2 peaks resulted from thermal denaturation of 2 kinds of A subunits in aldolase.

Key words: HYDRATE, ENTHALPY, DIFFERENTIAL SCANNING CALORIMETRY, THERMOCHEMICAL PROPERTY, ALDOLASE, PROTEIN, THERMOGRAPHY