Enzymatic degradation studies of xylogalacturonans from apple and potato, using xylogalacturonan hydrolase

Action of xylogalacturonan hydrolase (XGH) towards xylogalacturonan (XGA) present in the alkali saponified modified hairy regions from potato and apple pectin was studied. Analysis of enzymatic degradation products from XGA in these complex pectins demonstrated that the degradable xylogalacturonans from both sources have a similar xylose side chain distribution. The disaccharide beta-D-Xyl-(1,3)-GalA was the predominant product from these substrates. The number of enzymatic degradation products from xylogalacturonan present in apple and potato pectin was much lower than the number of products from a xylogalacturonan derived from Gum Tragacanth. This suggests a relatively uniform distribution of xylose in the degradable part of XGA from apple and potato pectin. In addition, dimeric side chains of xylose were observed in digests of XGA from both pectins, which apparently did not hinder the action of XGH. From this it is assumed that Xyl-Xyl as well as Xyl substituted GalA residues are accepted in subsite -1 of xylogalacturonan hydrolase. (c) 2006 Elsevier Ltd. All rights reserved.