Pyrophosphate:Fructose-6-Phosphate 1-Phosphotransferase and Fructose 2,6-Bisphosphate in the Bundle Sheath of Maize Leaves

The aim of this work was to discover whether the cells of the bundle sheath of the leaves of maize (Zea mays) contained pyrophosphate:fructose-6-phosphate 1-phos-photransferase (PFP) and fructose 2,6-bisphosphate (Fru-2,6-P2). Physiologically active preparations of bundle sheath cells from leaves of 4- to 6-week-old plants showed activities of PFP, 6-phosphofructo-2-kinase (6-PF-2-K), and fructose-2,6-bisphosphatase (Fru-2,6-Pase) of 38, 1.8, and 15 nmol min−1 mg−1 chlorophyll, respectively, and contained 75 pmol mg−1 chlorphyll Fru-2,6-P2. For the above enzymes, and marker enzymes for the bundle sheath and for mesophyll cells, the ratios of the activities in leaf extracts to those in bundle sheath extracts were determined. The ratios for PFP, 6-PF-2-K, Fru-2,6-Pase, and Fru-2,6-P2 were intermediate between those found for the mesophyll markers and bundle sheath markers. The distribution of PFP activity after nonaqueous fractionation of leaves differed from that of the bundle sheath and mesophyll marker enzymes. It is argued that maize bundle sheaths can contain significant activity of PFP and amounts of Fru-2 ,6-P2.