Soll, Jürgen; Wötzel, Christiane; Buchanan, Bob B.
Enzyme Regulation in C4 Photosynthesis. Identification and Localization of Activities Catalyzing the Synthesis and Hydrolysis of Fructose-2,6-Bisphosphate in Corn Leaves.
In: Plant Physiology, Vol. 77, Nr. 4: S. 999-1003
Activities catalyzing the synthesis of fructose-2,6-bisphosphate (fructose-6-phosphate,2-kinase or Fru-6-P,2K) and its breakdown (fructose-2,6-bisphosphatase or Fru-2,6-P2ase) were identified in leaves of corn (Zea mays), a C4 plant. Fru-6-P,2K and Fru-2,6-P2ase were both localized mainly, if not entirely, in the leaf mesophyll cells. A partially purified preparation containing the two activities revealed that the kinase and phosphatase were regulated by metabolite effectors in a manner generally similar to their counterparts in C3 species. Thus, corn Fru-6-P,2K was activated by inorganic phosphate (Pi) and fructose-6-phosphate, and was inhibited by 3-phosphoglycerate and dihydroxyacetone phosphate. Fru-2,6-P2ase was inhibited by its products, fructose-6-phosphate and Pi. However, unlike its spinach equivalent, corn Fru-2,6-P2ase was also inhibited by 3-phosphoglycerate and, less effectively, by dihydroxyacetone phosphate. The C4 Fru-6-P,2K and Fru-2,6-P2ase were also quite sensitive to inhibition by phosphoenolpyruvate, and each enzyme was also selectively inhibited by certain other metabolites.