Abstract
1. The temperature coefficient of erythrocyte cholinesterase was found as 1.3 and that of serum cholinesterase as 1.5.
2. The heat of activation of erythrocyte cholinesterase and serum cholinesterase were determined as 3.7 kcal./mole and 7.7 kcal./mole respectively.
3. The thermodynamic constants in the enzymatic reactions of cholinesterase in both types were calculated from the relationships be-tween the Michaelis constant respectively the dissociation constant of ESS and the temperature.
The present investigation was supported by Prof. K. Kaziro whom the author's deep gratitude is expressed. The author is also grateful for helpful advices given by Dr. Y. 0gura of Botanical Section, Faculty of Science, Tokyo University.
