Steady-state kinetic study of action of ribonuclease A, involving a conformational change between 30 and 40 degrees C.

The steady-state kinetics of the reaction of ribonuclease A with cyclic cytidine 2',3'-phosphate as substrate are investigated as a function of temperature at pH 5 and ionic strength 0.1 M. The results suggest, but cannot prove, that a conformational change near 32 degrees C is involved in the rate-limiting step of the reaction mechanism. This conformational change is proposed to be the same one that was observed in studies of the free enzyme and of enzyme-inhibitor complexes near the same temperature.