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 (ΔNO
3--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 ΔNO
3--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 ΔNO
3--ATPase for Na
2-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 MgSO
4 and Na
4PP
1 concentrations for the PPase activity of the three CAM species were approximately 2 mM and 0.16 mM, respectively. The optimum temperature for the ΔNO
3--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 ΔNO
3--ATPase and PPase activities in pineapple was less than that in the two Kalanchoe species. Thus, pineapple obviously maintained high tonoplast ΔNO
3--ATPase and PPase activities at high temperatures.
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