SummaryBy screening a cDNA library of artichoke (Cynara scolymus} blosssom discs for fructosyltransferases, we isolated a clone designated Cy21. The deduced amino acid sequence shows homology to acid J~-fructosyl hydrolases and to the sucrose-fructan 6-fructosyltransferase (6-SFT) of barley. Transiently expressed in Nicotiana tabacum

A newly isolated cDNA clone, Cy3, encoding the fructan fructan 1-fructosyltransferase (1-FFT) from artichoke was expressed using tobacco protoplasts as expression system. Analysis of the inulin molecules synthesized upon incubation of protoplast extracts with a mixture of oligofructans (DP3^5) shows the production of inulins with a degree of polymerization (DP) of up to 23, whereas parallel experiments performed using a 1-FFT cDNA from Jerusalem artichoke led to the production of fructans with a DP of up to only 12. The results of in vitro fructan synthesis catalyzed by transiently expressed enzymes therefore reflect the difference of in vivo fructan composition of Jerusalem artichoke (M h = 8^10) and artichoke (M h = 65). These data suggest that the fructan pattern in a given species is mainly defined by the enzymatic characteristics of 1-FFT.z 1998 Federation of European Biochemical Societies.