PURIFICATION AND CHARACTERIZATION OF FRUCTANS WITH BETA-2,1-GLYCOSIDIC AND BETA-2,6-GLYCOSIDIC LINKAGES SUITABLE FOR ENZYME STUDIES

Fructan pentasaccharides were purified, in quantities suitable for use as substrates for enzyme assays, from Neosugar-P (Meiji Seika Kaisha Ltd., Japan), tubers of Helianthus tuberosus L., and stems and leaf sheaths of Triticum aestivum L. by a combination of gel-filtration and RP-HPLC. Fructan of higher molecular mass (mean DP = 30) was purified from leaves of Lolium rigidum Gaud. that had been induced to accumulate fructan and characterized along with the commercially available fructan from Cichorium intybus L. (Sigma, St Louis, USA) (mean DP = 33). The fructan pentasaccharide purified from H. tuberosus was found to contain exclusively 2,1-linked fructose and terminal fructose and terminal glucose, and was identified as (1,1,1)-kestopentaose. The fructan pentasaccharide purified from Neosugar-P also contained (1,1,1)-kestopentaose, although the presence of 3% 1,6-linked glucose and 1% 2,6-linked fructose indicated that a small proportion of other kestopentaoses were present. The fructan pentasaccharide purified from T. aestivum consisted of almost exclusively 2,6-linked fructose and terminal glucose and terminal fructose and was considered to contain predominantly (6,6,6)-kestopentaose. The presence of 1% 2,1,6-linked fructose indicated the sample also contained a small proportion of branched kestopentaose. The high molecular mass fructan from C. intybus was found to comprise linear molecules containing only 2,1-linked fructose, terminal glucose and terminal fructose. High molecular mass fructan from L. rigidum contained predominantly 2,6-linked fructose, had predominantly internal glucose, indicated by 2% 1,6-linked glucose, low levels of branching, indicated by 2% 2,1,6-linked fructose residues and 1% of the residues were 2,1-linked fructose.