Enzymes with Activity Toward Xyloglucan
Xyloglucans are plant cell wall polysaccharides, which belong to the hemicellulose class; i.e., they can bind to cellulose. They are the most abundant hemicellulose in the walls of many nongraminaceous species. Xyloglucans can function both as a structural and as a reserve polysaccharide. In the primary cell wall, xyloglucans can crosslink cellulose ﬁbers, yielding a network that determines to a large extent the strength of the wall. This complex usually constitutes approximately half of the amount of wall polysaccharides, the cellulose (30%) being a bit more abundant than the xyloglucan (20%). Plants possess many enzymes to remodel this network. Certain degradation products of xyloglucan may serve as signaling molecules, the activity of which can be regulated by various glycosidases. Structural xyloglucans are also important from a food industry point of view. They are an important target for fungal enzymes in applications, which aim at a complete degradation of the plant cell wall, such as the ‘‘liquefaction process’’ for fruit juice manufacturing. Further, xyloglucans might play a role in determining the shelf life of fruits and vegetables.