Xyloglucan hydrolysis

The methods of Valent et al. (1980) and McNeil et al. (1982b) have been applied to the rigorous characterization of a nonasaccharide derived from the enzymic degradation of sycamore cell wall xyloglucan. Following partial acid hydrolysis and workup, 16 alkylated oligosaccharide-alditols were isolated by reverse-phase HPLC, but only 12 were sufficiently pure to be unambiguously characterized. 

The structural xyloglucan molecules in the plant cell wall are subject to partial degradation in vivo [39-42]. This degradation, which may loosen the cell wall and thus favour cell expansion [6,43], was widely assumed to be due to hydrolysis, catalysed by cellulases. Recently, however, xyloglucan has been found to undergo a novel reaction in vivo — catalysed by XET [25,26,31,38,44-46]. The action of XET is proposed to occur in two steps -... 

Within 10 minutes after lAA application, rapid response mechanisms result in coleoptile and stem segment cell wall deformation and elongation (13). Changes in cell metabolism appear to occur which result in the rapid pumping of protons across the cell plasma membrane and a resulting acidification of the cell wall. This acidification leads by an unknown mechanism to the hydrolysis of noncovalent crosslinks between xyloglucan polymers and the cellulose microfibrils of the cell wall. The cross links are later reformed in the enlarged cell (14). 

There is a clear need for a specific labelling method for carbohydrates on heterogenous fibres. Antibodies can be used as specific markers for carbohydrates. Oligosaccharides derived from xylan by acid hydrolysis (10) and from xyloglucan by cellulase hydrolysis (//) have been used as antigens for production of polyclonal antibodies. Polymeric carbohydrates have also been used as antigens for antibody production (12-14). 

Hemicellulases are groups of enz5mies belonging to glycosidases families, whose common feature is hydrolysis of hemicellulose. This polysaccharide has a complex structure consisting of linear and branched chains made up of xylane, arabinoxylan, xyloglucan. 

The structures and mole % of the total xyloglucan accounted for by each of these peaks are summarized in Fig. 6. The location of the Fuc-(1 2)-Gal disaccharide in the nonasaccharide was not originally determined (57). It has since been determined by partial enzymic hydrolysis of the nonasaccharide and isolation of the resulting definitive pentasaccharide labeled d in Fig. 6 (729). 

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