FRUCTAN EXOHYDROLASE ACTIVITY IN LEAVES OF LOLIUM-TEMULENTUM L

Crude extracts from leaves of Lolium temulentum L. exhibited invertase activity and activity capable of releasing fructose from fructans (fructan exohydrolase; FEH). The optimum pH for FEH activity was between pH 4.8 and 5.5. When shoots of 10-d-old seedlings were induced to accumulate fructans by cooling their roots to 5-degrees-C and exposing them to continuous light, FEH activity declined by at least 50%. FEH activity increased when the shoots were induced to mobilize the fructans by warming the roots to the ambient temperature (20-degrees-C) and darkening the plants. Declining activity coincided with loss of one of at least two FEH isoforms observed after starch gel electrophoresis. Partially purified FEH from leaves of L. temulentum was inhibited when assayed in the presence of 10 mM sucrose.