Actomyosin $Ca^{++}$ Activated Adenosinetriphosphatase 활성도에 대한 pH 및 온도의 영향

pH-Temperature Dependence of the Ca-ATPase Activity in Actomyosin Systems of Rabbit and Frog Skeletal muscle

  • 김희중 (연세대학교 의과대학 생리학교실) ;
  • 황애란 (연세대학교 의과대학 생리학교실) ;
  • 박양생 (연세대학교 의과대학 생리학교실) ;
  • 강두희 (연세대학교 의과대학 생리학교실)
  • Kim, Hee-Joong (Department of Physiology Yonsei University College of Medicine) ;
  • Hwang, Ae-Ran (Department of Physiology Yonsei University College of Medicine) ;
  • Park, Yang-Saeng (Department of Physiology Yonsei University College of Medicine) ;
  • Kang, Doo-Hee (Department of Physiology Yonsei University College of Medicine)
  • 발행 : 1977.12.31

초록

The activity of the $Ca^{++}$ activated adenosinetriphosphatase (Ca-ATPase) of actomyosin systeme of rabbit and frog skeletal muscle has been studied at varying pH and temperature. The PH optima of the Ca-ATPase activity of the rabbit actomyosin was rather broad. Over the temperature range of $16-36^{\circ}C$ activity of the enzyme was not appreciably changed between pH 6.4-8.5; below and above which it rapidly reduced. The pH at the inflection point of the enzyme activity increased as temperature decreased, showing the ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ of approximately $-0.018\;unit/^{\circ}C$. Consequently, $(OH^-)/(H^+)$ ratio at the inflection point was constant regardless of assay temperature. In the frog actomyosin systems the Ca-ATPase activity was not apparently altered between PH 6.4-7.0 when the incubation temperature was $15{\sim}30^{\circ}C$. Outside of this range of pH, however, the enzyme activity was dramatically decreased. The pH of the inflection point changed inversely with temperature. ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ at the acidic side was approximately $-0.018\;unit/^{\circ}C$, whereas that at the alkaline side it was about $-0.037\;unit/^{\circ}C$. The Arrhenius Plot on the Ca-ATPase activity at constant $(OH^-)/(H^+)$ ratio of 1.0 was not linear, but showed break at arround $20^{\circ}C$ for both rabbit and frog actomyosin Preparations. From these results it was speculated that pH dependence of Ca-ATPase activity of rabbit actomyosin systems might reflect titrations of histidine-imidazole and -SH groups, and that of the frog actomyosin represents titrations of histidine-imidazole and lysyllysine ${\alpha}-NH_2$ groups.

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