Sycamore cells

Many XGs are acetylated [248,278,279]. XG isolated from the spent media of suspension-cultured sycamore cells Glcp contains acetyl groups at positions 3, 4, or 6 [2]. 

Distribution of galacturonic acid (GalA) in the pectic polysaccharides of sycamore cell... 

Arabinose Sycamore cell suspensions 15.2 Tobacco cell suspensions 2.6... 

Stoddart, R.W. and Northcote, D.H. (1967) Metabolic relationships of the isolated fractions of the pectic substances of actively growing sycamore cells. BiochemJ. 105 45-59. 

Darvill, J. E., McNeil, M., Darvill, A. G., Albersheim, P. (1980). Structure of plant cell walls XL Glucuronoarabi-noxylan. A second hemicellulose in the primary cell walls of suspension-cultured sycamore cells. Plant Physiol, 66,1135-1139. 

Keegstra, K., Talmadge, K. W., Bauer, W. D., Albersheim, P. (1973). The structure of plant cell walls. III. A model of the walls of suspension-cultured sycamore cells based on the intercormections of the macromolecular components. Plant Phyiol., 51,188-196. 

Linkage analysis of the polymer isolated from suspension-cultured, sycamore cells indicated55,65 ratios of 2-linked rhamnosyl to 2,4-linked rhamnosyl to 4-linked galactosyluronic residues of 1 1 4 (see Fig. 1). 

Clearly, branched arabinans are important, primary cell-wall components, but considerable further study is needed before it will be possible to draw even a tentative structure for the intact-wall component. Isolation and analysis of the arabinan of sycamore cell-wall is of current interest, a study augmented by the availability of two purified enzymes, endo-a-(l— 5)-arabinanase63 133 and exo-a-arabinosidase.63... 

Those galactans that have been studied (see the preceding) have degrees of polymerization ranging from 33 in white willow161 to 50 in sycamore-cell primary-walls.183 These values were obtained by vapor pressure and osmosis studies,161 and by comparing the ratio of terminal to intrachain galactose units by methylation analysis.163... 

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... 

This evidence indicated the presence of two hydroxy-L-proline-rich glycoproteins in the primary cell-wall of suspension-cultured sycamore-cells one, a structural glycoprotein found only in the wall, and the second which, in culture, is present in the wall in only small proportions and is mainly found in the culture medium.57,234 These two glycoproteins appear to be unrelated structurally. 

In earlier Sections, the individual polymers that make up the constituent parts of the primary cell-wall have been discussed, and partial structures proposed for some of these polymers are shown in Figs. 1-4. A model of the primary cell-wall of suspension-cultured sycamore-cells, illustrating proposed interconnections between these constituent polymers within the intact wall, has been constructed by Albersheim and his associates.5,10 57,64,65 The model, not designed to be spatially or quantitatively accurate, is depicted in Fig. 6. 

The hydroxy-L-proline-rich protein present in the culture medium of suspension-cultured sycamore-cells was shown to be covalently linked to an arabinogalactan,57 and this led to speculation regarding the existence of a similar interconnection within the cell wall. However, it has now been established that the hydroxy-L-proline-rich protein of the primary wall is structurally different from that present in the extracellular fluid234 (see Section VII, 1), and thus the latter cannot be used as a model for the cell-wall glycoprotein. 

When this enzyme acts on (1— 5)-L-arabinan, arabino-oligosaccha-rides are produced in the initial stage of the reaction. The end products are L-arabinobiose andL-arabinose. When the strain F-l 1 enzyme acts on (1— -L-arabinan, the extent of decomposition is4 23.3%, whereas, that of beet L-arabinan is only 3.3%. This enzyme is inactive towards phenyl and p-nitrophenyl a-L-arabinofuranoside, arabinoxylan, arabinogalac-tan, and gum arabic. These results led to the conclusion that endo-L-arabinanase preferentially cleaves 5-linked arabinosyl residues. The action of endo-L-arabinanase on L-arabinan produces arabino-oligosaccharides, from which L-arabinotriose was isolated.27 When acting upon cell walls obtained by sycamore-cell cultivation, this enzyme releases L-arabinan.27... 

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