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

抄録

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 Kalanchoe pinnata and K. daigremontiane, starch-utilizing species with high ATP-PFK activities, were investigated. The ATPase and nitrate-sensitive ATPase (ΔNO₃^--ATPase) activities were higher than the PPase activity of pineapple, but the reverse was the case in the two Kalanchoe species. The optimum pH for ΔNO₃^--ATPase in pineappe, 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 K_m of ΔNO₃^--ATPase for Na₂-ATP for pineapple, K. daigremontiana and K. pinnata was 0.47, 0.48 and 0.43 mM, respectively, and V_max 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 ΔNO₃^--ATPase in pineapple, K. daigremontiana and K. pinnata was 35∼43, 35∼43 and 37°C, respectively, and that for PPase was 46∼49°C. In addition, at a high temperature, the decrement of tonoplast ΔNO₃^--ATPase and PPase activities in pineapple was less than that in the two Kalanchoe species. Thus, pineapple obviously maintained high tonoplast ΔNO₃^--ATPase and PPase activities at high temperatures.