ADENOSINETRIPHOSPHATASE ACTIVITY OF MICROSOMES FROM RABBIT SKELETAL MUSCLE; ITS GENERAL ENZYMIC PROPERTIES AND RELATION TO PHYSIOLOGICAL FUNCTION OF MICROSOMES

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The microsomal fraction of rabbit skeletal muscle was isolated and its ATPase activity was studied, in connection with the physiological function of the microsomes. The following results were obtained.
1. From its enzymic properties, it was suggested that the microsomal ATPase is the same as the Kielley-Meyerhof one.
2. The ATPase was activated by several long chain fatty acids, slightly affected by Na⁺or K⁺and not inhibited by ouabain.
3. In the presence of oxalate, the extra splitting of ATP by the addition of Ca⁺⁺was confirmed. The rate of ATP hydrolysis in the “extra-splitting phase” was decreased and the length of this phase was increased with increase in the amount of Ca⁺⁺. The extra splitting of ATP was not affected by thepreincubation of the microsomes with ATP. The extra splitting of ATP was scarcely affected by caffeine and ouabain, while DNP modified remarkably this ATP splitting.
The author wishes to express his thanks to Prof. Dr. T. NAGAI and Prof. Dr. E. MIYAZAKI for their support and encouragement throughout this investigation.