토마토 뿌리조직에서 분리한 마이크로솜 이온펌프의 특성 = Characterization of Microsomal ATPases Prepared from Tomato Roots

다국어 초록 (Multilingual Abstract)

Microsomes of tomato roots were prepared and the activities of microsomal ATPases were measured in order to understand the molecular mechanisms of various ion transports. The activities of plasma membrane H^+-ATPase and vacuolar H^+-ATPase were evaluated to ∼30% and ∼38% of total microsomal ATPase activity by using their specific inhibitor, vanadate and nitrate (NO₃^-), respectively. The inhibitory effects of vanadate and NO₃^- were additive and the simultaneous additions of these two inhibitors decreased the total activity up to 50∼70%. The microsomal ATPase activity was regulated key pH and the maximal activity was obtained at pH 7.4. The activity of microsomal ATPase was increased by K^+ up to ∼30% at the concentration of K^+ above 10 mM. However, the K^+- induced increase in the activity was Completely inhibited by the simultaneous addition of Na^+. To identify the ATPase activity regulated by K^+, the effects of specific inhibitors were measured. Vanadate and NO₃^- inhibited total ATPase activity by 27% and 32% in the absence, of K^+ and by 27% and 40% in the presence of 120 mM K^+, respectively. These results suggest that K^+ increases the activity of NO₃^--sensitive vacuolar H^+-ATPase but not that of vanadate-sensitive plasma membrane H^+-ATPase since vanadate has no effect on K^+-induced increase in ATPase activity. The microsomal ATPase activity was also decreased by increasing Ca^(2+) concentration. Interestingly, NO₃^- blocked the Ca^(2+)-induced inhibition of microsomal ATPase activity; however, vanadate had no effect. These results imply that vacuolar H^+-ATPase is activated by K^+ and inhibited by Ca^(2+).