Synthesis of Arabinose-Containing Cell Wall Precursors in Suspension-Cultured Tobacco Cells IV. Differential Subfractionation and Comparison of the Acidic Precursors

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A series of ^<14>C-arabinose-labelled cell wall precursors were differentially subfractionated to compare their properties and analyze their sugar side chains. The ratio of radioactivity/protein of the subfractions increased 100- to 5,000-fold from that of the starting homogenate. The less acidic fractions showed higher ratio of radioactivity/protein. Molecular weights of these fractions' constituents were distributed mostly between 130,000 and 150,000 and their dispersion in each fraction was small. The chemical composition of the fractions, which was rather invariable, was that of the typical arabinogalactan protein, however, a low content of protein and uronic acid was noticed in the less acidic fractions which showed the highest radioactivity/protein ratio . Gel chromatography of an alkaline hydrolysate of these subfractions indicated that the precursors consisted of two kinds of molecules: 1) a less acidic polysaccharide of high radioactivity/protein ratio, probably arabinogalactan, and 2) a more acidic arabinogalactan protein of low specific radioactivity/protein ratio. The average size of the side chains of the arabinogalactan protein was about 10,000 and linked to about 70% of the hydroxyproline residues. No small oligosaccharide side chain (DP<13) was found. Also, no precursor-product relationship was observed between these subfractions.
日本植物生理学会の論文