Xyloglucans structure

This essay was written in an attempt to explain our overview of primary cell walls and to reach consensus on the nomenclature of primary cell wall polysaccharides. We present evidence supporting the hypothesis that cellulose, xyloglucan, arabinoxylan, homogalacturonan, RG-I, and RG-II are the six polysaccharides common to all primary cell walls of higher plants. In many cells, these six polysaccharides account for all or nearly all of the primary wall polysaccharides. Like the physically interacting proteins that constitute the electron transport machinery of mitochondria, the structures of the six patently ubiquitous polysaccharides of primary cell walls have been conserved during evolution. Indeed, we hypothesize that the common set of six structural polysaccharides of primary cell walls have been structurally... 

Figure 3.1 Structures of cellulose and two types of xyloglucans, a fucogalactoxyloglucan and an arabinoxyloglucan.

Sims, 1. M., Munro, S. L. A., Currie, G., Craik, D., Bacic, A. (1996). Structural characterisation of xyloglucan secreted by suspension-cultured cells oiNicotianaplumbaginifolia. Carbohydr. Res., 293, 147-172. 

Similar structural problems exist for the distribution of side chains in galactoglucomannans, xyloglucans, arabinoxylans, and 4-0-methylglucuronoxylans, and even for the distribution of acetyl groups in glucomannans and for related features in many other polysaccharides. 

All of the aforementioned xyloglucans share common structural features, although the glycosyl composition varies somewhat with the source. They all possess a backbone of 4)-linked D-glucosyl resi-... 

The structure of the xyloglucans from the walls and culture medium of suspension-cultured sycamore-cells has been investigated by Alber-sheim and associates56 by utilizing purified endo-/ -(l— 4)-glucanase for... 

Such products would be expected to arise from similar treatment of xyloglucans from dicots. However, if xyloglucan is present in primary cell-walls of monocots, it is clearly there in much smaller proportions than in dicot primary-walls, and it may not assume the structural significance that this polysaccharide has in the latter. 

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