PURIFICATION AND CHARACTERIZATION OF THE ENZYMES OF FRUCTAN BIOSYNTHESIS IN TUBERS OF HELIANTHUS-TUBEROSUS COLOMBIA .1. FRUCTAN-FRUCTAN FRUCTOSYL TRANSFERASE

Fructan:fructan fructosyl transferase (FFT), one of the enzymes involved in the synthesis of beta-2,1 linked fructose polymers has been purified 205-fold from tubers of Helianthus tuberosus harvested in the accumulation phase. The molecular weight of the native as well as the SDS-denatured protein is approximately 70 kDa. On IEF, the protein was separated into five molecular species with pi Values between pH 4.5-5.0. The optimum pH for fructosyl transfer activity was between 5.5-7.0. Temperature optimum was in the range of 25-35 degrees C; the Q(10) value between 25 and 5 degrees C was 1.14. FTT catalysed the self-transfer of fructosyl groups with GF(2), GF(3), GF(4) or GF(5) as substrate and acceptor. The rate of self-transfer with both GF(2) and GF(3) increased linearly with substrate concentration up to 100 mol m(-3) and was still not saturated at 600 and 300 mol m(-3), respectively. FFT was unable to hydrolyse GF or to catalyse the self-transfer with GF but could mediate the transfer of fructosyl units from inulin on to GF.