Characteristics of Adenosinetriphosphatase and Inorganic Pyrophosphatase in Tonoplasts Isolated from Three CAM Species, Ananas comosus, Kalanchoë pinnata and K. daigremontiana

The characteristics of adenosinetriphosphatase (ATPase) and inorganic pyrophosphatase (PPase) in the tonoplasts isolated from leaf mesophyll homogenates of Ananas comosus (pineapple), a hexose-utilizing species with high PPi-PFK activities, and Kalanchoë pinnata and K daigremontiana, starch-utilizing species with high ATP-PFK activities, were investigated. The ATPase and nitrate-sensitive ATPase (⊿NO3–-ATPase) activities were higher than the PPase activity of pineapple, but the reverse was the case in the two Kalanchoë species. The optimum pH for ⊿NO3–-ATPase in pineapple, K. daigremontiana and K pinnata was 7.0∼8.25, 7.5∼8.25 and 7.5∼8.25, respectively, and that for PPase was 6.5∼7.5 in all species. The Km of ⊿NO3–-ATPase for Na2-ATP for pineapple, K. daigremontiana and K pinnata was 0.47, 0.48 and 0.43 mM, respectively, and Vmax was 52.6, 27.0 and 40.0 μmol Pi mg–1 protein h–1, respectively. The optimum MgSO4 and Na4PP1 concentrations for the PPase activity of the three CAM species were approximately 2 mM and 0.16 mM, respectively. The optimum temperature for the ⊿NO3–-ATPase in pineapple, K. daigremontiana and K. pinnata was 35∼43, 35∼40 and 37°C, respectively, and that for PPase was 46∼49°C. In addition, at a high temperature, the decrement of tonoplast ⊿NO3–-ATPase and PPase activities in pineapple was less than that in the two Kalanchoë species. Thus, pineapple obviously maintained high tonoplast ⊿NO3–-ATPase and PPase activities at high temperatures.