Degradation of apple fruit xyloglucan by endoglucanase

A purified, alkali-extractable apple fruit xyloglucan (APfxg) was treated by endoglucanase (endoIV) from Trichoderma viride. The degradation products were fractionated by size-exclusion chromatography on BioGel P-2; the pentamer to dodecamer fractions were further fractionated by semi-preparative high-performance anion-exchange chromatography. The purified oligosaccharides were characterized by monosaccharide analysis, mass spectrometry and degradation with Driselase. Based on these data, tentative structures were proposed for most products. Apple xyloglucan is composed of a diversity of repeating units. Next to the major oligosaccharides XXXG, an octamer, XXFG and XLFG (Renard, C.M.G.C., Lomax, J.A. & Boon, J.J. (1992). Carbohydr. Res., 232, 303-320), XG, XXG, FG and two new fucose-containing oligosaccharide building blocks (hexasaccharide and dodecasaccharide) were found. Larger xyloglucan fragments were obtained by partial degradation of APfxg by endoIV, and treatment of apple cell wall material by endoI. These fragments were predominantly composed of fucose-containing oligosaccharides. Our results show that both endoIV and endoI are hindered by fucosylated side chains. Copyright (C) 1996 Elsevier Science Ltd