Studies on the regulating mechanism of CAM photosynthesis under high night temperature

当夜间温度维持在36ºC以上时，凤尾莲和凤尾莲的光合作用由CAM向C3转变，而凤尾莲的光合作用没有发生变化。本研究从糖酵解调控的角度探讨了CAM向C3转化的机理。两种kalanche的atp依赖性磷酸果糖激酶（PFK）在35℃时表现出最优的活性，而A.comosus的ppi依赖性PFK的活性最高可达40℃。麻草的PPi-PFK在pH7.2和7.6两个峰处表现出最优值，卡兰科的ATP-PFK在pH 7.6处表现出最优值。麻草PPi-PFK的等电点由白天的pH4.88和5.34两种类型转变为夜晚的pH4.80类型。在deab -纤维素柱层析上，白白和夜间都能洗脱出麻草中PPi-PFK的两个峰。每个PPi-PFK蛋白的洗脱时间分别为14 mm和12 mm。而离子层析上电荷密度较大的PPi-PFK蛋白被分离为两种蛋白。在夜间高温条件下，被称为PEPcase活化剂的葡萄糖6-磷酸含量的增加被抑制。综上所述，糖酵解在CAM光合作用的调控中发挥了重要作用。

When a night temperature higher than 36ﾟC was maintained, Kalanchoe daigremontiana and K.pinnata shifted from the CAM photosynthesis to C3 photosynthesis, but Ananas comosus did not alter its photosynthesis. In this study, the shifting mechanism from CAM to C3 was investigated on the aspect of glycolysis regulation. ATP-dependent phosphofructokinase (PFK) of the two Kalanchoe species exhibited an optimum temperature of the activity at 35'C, but PPi-dependent PFK of A.comosus increased the activity up to 40ﾟC.PPi-PFK of A.comosus exhibited two optimum peaks of pH7.2 and 7.6, and ATP-PFK of the Kalankoe species showed an optimum pH of 7.6. Isoelectric point of A.comosus PPi-PFK was changed from two type of pH4.88 and 5.34 in day-form to one type of pH4.80 in night-form. PPi-PFK of A.comosus was eluted as two peaks on DEAB-cellulose column chromatography in both day and night. Each PPi-PFK protein showed ca. 14 mm. and ca. 12 mm. of elution time on size-exclusion chromatography. However, the PPi-PFK protein with large charge density on ion-chromatography was separated to the two proteins. Under high night temperature condition, the increase of glucose 6-phosphate content, which was known as an activator of PEPcase, was depressed in Kalanchoe. As shown above, it was suggested that the glycolysis played an important role in the regulation of CAM photosynthesis.