Fructosan metabolism in Cichorium intybus roots

Abstract Incorporation of [ 14 C]sucrose into difructosyl glucose (F 2 G), trifructosyl glucose (F 3 G) and tetrafructosyl glucose (F 4 G) in the presence of various nucleoside triphosphates revealed that formation of F 4 G and F 3 G is retarded in the presence of ATP, and formation of F 3 G and F 2 G is significantly enhanced in the presence of CTP, whereas UTP has no effect on the synthesis of these oligosaccharides. Different fructosyl transferases seem to be responsible for the different fructosylation steps and self transfer seems to be the major pathway for fructosan synthesis. Utilization of added glucose, which is formed by sucrose sucrose fructosyl transferase action in vivo , is completely inhibited in acetate buffer whereas in phosphate, citrate and citrate-phosphate buffers glucose is actively utilized. In the presence of fluoride ions both glucose utilization and its conversion to CO 2 is inhibited by ca 50%. CO 2 production from [ 14 C]glucose is completely inhibited in acetate ions. No evidence for the incorporation of 14 C from [ 14 C]glucose into [ 14 C]sucrose is observed. The ratio of bound fructose to bound glucose is the same in the entire length of the root indicating that there is no preferential zone for fructosan synthesis.