xyloglucan-specific exo-β-1,4-glucanase

The enzyme removes XXXG heptasaccharides, XXLG/XLXG octasaccharides and XLLG nonasaccharides from the end of tamarind seed xyloglucan polymers in a processive manner. Hydrolysis occurs at the unsubstituted D-glucopyranose residue in the main backbone. It is not known whether the cleavage takes place at the reducing or non-reducing end of the polymer. Very low activity with β-D-glucans. The enzyme from Chrysosporium lucknowense shifts to an endoglucanase mode when acting on linear substrates without bulky substituents on the polymeric backbone such as barley β-glucan. Reaction: Hydrolysis of (1→4)-D-glucosidic linkages in xyloglucans so as to successively remove oligosaccharides from the chain end.