[Mechanism of thermal denaturation of native trypsin and trypsin modified by neutral soluble polymer]

The thermal denaturation of trypsin solutions and trypsin vinylpyrrolidone-acrolein copolymer conjugate was studied within the temperature range of 37.5-96 degree. pH 4.5. A mechanism for trypsin thermal denaturation based on its ability to form dimers and determining the minimal stability of the enzyme at 66 degree and its maximal stability at 74 degree is proposed. The thermal denaturation of the trypsin conjugate is of a different type, which depends on the changes in the thermal denaturation mechanism due to its incapability to form dimers. A decrease in the activation and thermodynamic parameters of the enzyme denaturation during its modification is due to the approximation of the protein structure to that of the denatured form, eventually resulting in the enzyme destabilization. The increased stability of the modified protein to the denaturating effects of low temperatures is due to the changes in the denaturation mechanism induced by enzyme modification.