Screening for hetero-transglycosylating activities in extracts from nasturtium (Tropaeolum majus)l

Using combinations of different polysaccharides as glycosyl donors and of oligosaccharides fluorescently labeled by sulforhodamine (SR) as glycosyl acceptors, we screened for the presence of transglycosylating activities in extracts from nasturtium (Tropaeolum majus). Besides xyloglucan endotransglycosylase/hydrolase (XTH/XET, EC 2.4.1.207) activity, which transfers xyloglucanosyl residues from xyloglucan (XG) to XG-derived oligosaccharides (XGOs), a glycosyl transfer from XG to SR-labeled cello-oligosaccharides and laminarioligosaccharides has been detected. The XGOs also served as acceptors for the glycosyl transfer from soluble cellulose derivatives carboxymethyl Cellulose and hydroxyethylcellulose. The effectivity of these polysaccharides its glycosyl donors for transfer to XG-derived octasaccharide [1-H-3]XXLGol decreased in the order XG > HEC > CMC. Isoelectric focusing ill polyacrylamide gels showed that bands corresponding to hetero-transglycosylase activities coincided with zones corresponding to XTH/XET. These results call be explained as due either to Substrate non-specificity of certain isoenzymes of XTH/XET or to existence of enzymes catalyzing a hetero-transfer, that is the formation of covalent linkages between different types of carbohydrate polymers. (c) 2006 Elsevier Ltd. All rights reserved.