IDENTIFICATION OF PRODUCTS FORMED BY A FRUCTAN-FRUCTAN FRUCTOSYLTRANSFERASE ACTIVITY FROM LOLIUM-RIGIDUM

The products formed by a fructan:fructan fructosyltransferase (FFT) ac tivity purified from Lolium rigidum Gaudin were identified after gas c hromatography-mass spectrometry of partially methylated alditol acetat es, electrospray ionization-mass spectrometry and reversed-phase high- performance liquid chromatography. The FFT activity synthesized oligof ructans up to degree of polymerization (DP) 6, but did not synthesize fructans of DP > 6 even when assayed with (1,1,1)-kestopentaose for up to 10 h. The FFT activity when assayed with 1-kestose or 6(G)-kestose synthesized fructan with fructosyl residues almost exclusively linked by beta-2,1-glycosidic linkages. When assayed with 1-kestose, the FFT activity synthesized tetrasaccharides and pentasaccharides with an in ternal glucosyl residue. The predominant tetrasaccharide was (1&6(G))- kestotetraose and the predominant pentasaccharide was (1&6(G),1)-kesto pentaose. By comparison, tetrasaccharides and pentasaccharides extract ed from L. rigidum also contained predominantly beta-2,1-glycosidic li nked fructans with an internal glucosyl residue. The only exception wa s that one of the pentasaccharides contained beta-2,1- and beta-2,6-gl ycosidic linked fructosyl residues. This pentasaccharide was not synth esized by the FFT activity. The role of this FFT activity in formation of oligofructans in L. rigidum is discussed.