Effect of temperature on the activity of ribonuclease from Tetrahymena pyriformis.

Intracellular ribonuclease from the ciliate Tetrahymena pyriformis GL was purified 10-fold. After preheating for 20 minutes at 100°C of the ribonuclease preparation 80% of its activity was lost. Preheating under the same conditions, however, in the presence of RNA, did not affect the enzyme activity. Between 0°C and 41°C the apparent activation energy was 15,600 cal per deg. per mole.