Regulatory properties of Fru-2, 6-P2on pyrophosphate : D-fructose-6-phosphate 1-phosphotransferase (PFP ; EC 2.7.1.90), its molecular weight and subunit structure in illuminated and darkened pineapple (Ananas comosus (L.) Merr. cv. Smooth-cayenne N67-10) leaf were investigated. Polyacrylamide gel electrophoresis and immunoblot revealed two subunits, α (66 kDa) and β (64.1 kDa) in desalted leaf extract. Diurnal PFP activity of pineapple showed the dependency on a day/night regulation. Glycolytic activity of PFP was dependent on pH, the degree of activation by Fru-2, 6-P2at pH 6.4 was 4.16 and 11.13 fold increases during the day and nighttime, respectively. But gluconeogenic reaction was only weakly affected by Fru-2, 6-P2at various pH. Activity of PFP was also strongly depended on temperature. In 10-40°C temperature regimes, glycolytic reaction of PFP activity showed about 2 fold activation by Fru-2, 6-P2in both day and night, but gluconeogenic reaction was weakly affected. In both reactions PFP activity of darkened leaf was always lower than that of day form. This suggested that nocturnal acidification of CAM in pineapple had significant influence on PFP. Results obtained in our experiment suggested that only a part of regulation of pineapple PFP was associated with Fru-2, 6-P2but some other factors were also responsible for PFP regulation.