CORRELATION BETWEEN STABILITY OF ALPHA-CHYMOTRYPSIN AT HIGH-TEMPERATURES AND SALTING-IN STRENGTH OF SOLUTION

A correlation between thermostability of alpha-chymotrypsin at 76-degr ees-C and the parameter of the Setchenov equation as a measure of ''sa lting-in'' (''salting-out'') strength of the solution has been found. Increasing the concentration of salting-in compounds (for example, pot assium rhodanide, urea, guanidinium chloride, or formamide) stabilizes the enzyme. The maximally achieved stabilization (almost 100-fold) is similar to those obtained by modification with hydrophilic reagents o r by immobilization. The stability of alpha-chymotrypsin at elevated t emperatures changes only insignificantly with increasing concentration of salting-out compounds. Additivity of changes in enzyme stability i s found for compounds with different salting-in and salting-out streng ths. The correlation is explained by the effect of the added compounds on the conformational equilibrium between the native and ''high-tempe rature'' forms of the enzyme, the latter being much more stable.