小麦根和叶细胞质膜Ca^(2+)-ATPase性质的比较

COMPARISON OF PROPERTIES OF THE PLASMA MEMBRANE Ca^(2+)-ATPase FROM WHEAT ROOT AND LEAF

比较了小麦(Triticum aestivum L.cv.Longchun No.13)根和叶细胞质膜Ca^(2+)-ATPase的性质,并结合二者所处的环境和功能方面的差异进行了分析。结果表明:根细胞质膜Ca^(2+)-ATPase在一个较宽的pH范围内有高活性,最适反应温度为45℃;叶细胞质膜Ca^(2+)-ATPase只在一个较窄的pH范围内有高活性,最适反应温度为50℃。根细胞质膜Ca^(2+)-ATPase对ATP的Hill系数为1.6,具有明显的正协同作用;叶细胞质膜Ca^(2+)-ATPase对ATP的Hill系数为1.0,符合米氏动力学类型。两种器官的细胞质膜Ca^(2+)-ATPase受Ca^(2+)激活的Hill系数都小于1,都具有负协同作用。钙调素对酶活性有激活作用,而Mg^(2+)则有抑制作用。

The properties of plasma membrane Ca2+-ATPases from wheat (Triticum aestivum L. cv.Longchun No.13) root and leaf were compared, and their different properties were analyzed in association with the differentia of the functions of these two organs and their relevant environments. Root plasma membrane Ca2+-ATPase showed a high activity in a broad range of pH and an optimum reaction temperature of 45C, while the leaf enzyme activated in a narrow range of pH and an optimum reaction temperature of 50C . Hill coefficient of root plasma membrane Ca2+-ATPase for ATP was 1.6, revealing an obvious positive cooperativity. In contrast, that of leaf plasma membrane Ca2+-ATPase was 1.0, being in keeping with Michaelis-Menten dynamics. For Ca2+ activation, Hill coefficient of plasma membrane Ca2+ -ATPases from both organs were less than 1, suggesting that both had negative cooperativity. The enzymes were activated by calmodulin and inhibited by Mg2+-