Plant Polysaccharide Xyloglucan and Enzymes That Hydrolyze It (Review)

Various types of plant raw material are widely used in the pulp and paper, textile, food, and agricultural industries and pharmacology. One of the problems of utilizing the complex plant biomass is poor knowledge of its hemicellulose content and the lack of effective enzymes for hydrolysis of hemicelluloses. Xyloglucan is the major structural and storage polysaccharide in all dicots and a great number of monocots. It has a branched architecture with a backbone constructed of β-1,4-connected cellotetraose units decorated with short sidechains composed of xylose, galactose, arabinose, fucose and some other residues. Sidechain composition and alternation order are specie-specific and can change during cell growth resulting in variety of xyloglucan structural types. In general, xyloglucan structure depends on the taxonomic position of the plant. Structural features of xyloglucans belonging to different taxonomic groups are discussed in the evolutionary aspect. Xyloglucan hydrolysis is a necessary condition during conversion of plant biomass into high added-value products. Variety of xyloglucan structural types complicates the selection of enzymes for its hydrolysis. Xyloglucanase-containing multienzyme complexes can be used for efficient decomposition of plant biomass polysaccharides into fermentable sugars for biotechnology, and for the improvement of feed quality. Investigation of xyloglucanases is necessary for the development of methods for protecting plants from pathogenic microorganisms, which use these enzymes in the invasion of plant tissue. The article discusses structural features of xyloglucans from different taxonomic groups in the evolutionary aspect and reviews selection of xyloglucanases for efficient hydrolysis of complex plant biomass.