Chloroplast Phosphofructokinase

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Abstract
Ammonium sulfate fractionation of an extract from the leaves of spinach (Spinacia oleracea L.) produced 2 fractions of phosphofructokinase [EC-2.7.1.11] activity, the 1st stimulated by Pi and the 2nd inhibited by Pi. Only the 2nd fraction was obtained from similar treatment of an extract of isolated spinach chlorlplasts. The 2 fractions differed distinctly with respect to kinetics for the substrate fructose 6-phosphate. Evidence for these 2 types of phosphofructokinase was also obtained with extracts from the leaves of wheat (Triticum aestivum L.), pea (Pisum sativum L.), and maize (Zea mays L.), and the glumes of oat (Avena sativa L.), but not from chive (Allium schoenoprasum L.), leaves, pea cotyledons, or peat roots. Apparently most leaves contain phosphofructokinase activity in chloroplasts as well as in the cytoplasm. Spinach chloroplast phosphofructokinase activity, which was at least 2.5 .mu.mol fructose 1,6-bisphosphate formed per mg chlorophyll/h, did not result from contamination by cytoplasm or by other cellular organelles, and was not detected until after chloroplasts were broken.