FRUCTAN EXOHYDROLASE ACTIVITIES FROM LOLIUM-RIGIDUM THAT HYDROLYZE BETA-2,1-GLYCOSIDIC AND BETA-2,6-GLYCOSIDIC LINKAGES AT DIFFERENT RATES

Five fructan exohydrolase activities from Lolium rigidum Gaudin were separated and partly purified by a combination of salt precipitation, affinity chromatography, gel-filtration chromatography, anion-exchange chromatography and isoelectric focusing. The activities were identified by incubating enzyme fractions with fructan from both Lolium rigidum and Cichorium intybus. On the basis of activities when (6,6,6)-kestopentaose and (1,1,1)-kestopentaose were used as substrates, it was concluded that three of the activities hydrolyzed beta-2,6-glycosidic linkages faster than beta-2,1-glycosidic linkages and two activities hydrolyzed beta-2,1-glycosidic linkages faster than beta-2,6-glycosidic linkages. Fructan exohydrolases that hydrolyze beta-2,1-glycosidic linkages faster than beta-2,6-glycosidic linkages, and fructan exohydrolases that hydrolyze beta-2,6-glycosidic linkages faster than beta-2,1-glycosidic linkages have not previously been identified together in a temperate grass. All fructan exohydrolases were inhibited markedly by sucrose. It is proposed that the classification of beta-fructofuranosidases be reconsidered because EC 3.2.1.80 is presently used to designate all fructan exohydrolases irrespective of the rates at which they hydrolyze beta-2,1- or beta-2,6-glycosidic linkages in fructans.