The Superprecipitation of Actomyosin and Its ATPase Activity in Low Concentration of ATP

抄録

1. The time course of superprecipitation and the ATPase activity of actomyosin gel were measured under low concentrations of ATP in the presence of an ATP regenerating system.
2. The initial rate of increase in turbidity of an actomyosin gel suspension during the process of superprecipitation induced by ATP was proportional to the concentration of ATP, if ATP was used in a reasonably low con-centration.
3. The apparent ATPase activity of acto-myosin gel was gradually decreased during the process of superprecipitation.
4. The decrease was not observed at a low temperature or in a high concentration of ATP.
5. The result is explained by the more limited diffusion of the substrate into the contracted actomyosin gel.
6. It is concluded that the ATPase activity of actomyosin gel remains unchanged during and after the process of superprecipitation.
7. A small amount of calcium affected neither the time course of superprecipitation, nor the ATPase activity under a low con-centration of ATP.
8. Increasing the potassium or sodium concentration caused the accelerated syneresis of actomyosin gel but did not appreciably affect its ATPase activity.
The author wishes to express his thanks to Prof. H. Kumagai for his encouragement and to Prof. S. Ebashi for suggesting this work and advices. The author is also indebted to Dr. F. Julian for his, assistance in preparing this manuscript. This work was supported in part by the grant-in-aid of U. S. Public Health Service, AM-04810, from National Institute of Arthritis and Metabolic Diseases, of the Rockefeller Foundation, RF60141, and also of Pharm-acological Research Foundation.