Fructose-2,6-bisphosphate: a traffic signal in plant metabolism

Fructose-2,6-bisphosphate (Fru-2,6-P 2) regulates key reactions of the primary carbohydrate metabolism in all eukaryotes. In plants, Fru-2,6-P 2 coordinates the photosynthetic carbon flux into sucrose and starch biosynthesis. The use of transgenic plants has allowed the regulatory models to be tested by modifying the Fru-2,6-P 2 levels and the enzymes regulated by Fru-2,6-P 2. Genes for the bifunctional plant enzyme that synthesizes and degrades Fru-2,6-P 2 have been isolated and molecular characterization has provided new insight into structure and molecular regulation of the enzyme. Advances in Fru-2,6-P 2 physiology and molecular biology are discussed. These advances have not only enlightened in vivo operation of Fru-2,6-P 2 but also revealed that the Fru-2,6-P 2 regulatory system is highly complex and interacts with other regulatory mechanisms.