Xylosyl- -glucose

By step (a), a picture could be formed of the kinetics of the intracellular incorporation of 3H from [3H]arabinose into the major polysaccharides of the cell wall. Radioactivity was incorporated into polymer-bound arabinose and xylosyl-glucose units after lag periods of about 3.5 min and... 

The enzymes involved are nucleoside diphosphohexosetransferases, probably GDP-D-mannosyltransferase (EC 2.4.1.32) and UDP-D-galactosyl-transferase. For a structurally related polymer, (1 - 6)-a-D-xylosyl-(l - 4)-/3-D-glucan, synthesis was shown to involve concurrent incorporation of D-xylose and D-glucose, and not substitution by D-xylose of a preformed (1 - 4)-/3-D-glucan chain.34 The insolubility of (1 - 4)-/3-D-glucan and man-nan would make the latter mechanism unlikely. 

The further application of the mercuric acetate method made possible the synthesis of primeverose [6-0-/3-D-xylosyl-D-glucose] and also isoprime-verose [6-O-a-D-xylosyl-D-glucose] from 2,3,4-tri-O-acetyl-a-D-glucosyl chloride and tri-O-acetyl-D-xylosyl bromide. After the preparation of these sugars in larger quantities, the naturally occurring primeverosides could... 

Fig. 5.—Sugars in Hydrolyzates of Total Hemicellulose from Oat Plants of Different Ages, Excluding Glucose but Including Uronic Acids Separately Determined.167 (It is assumed that, after hydrolysis, all uronic acids were present in aldobiouronic acids containing a xylose residue the proportions of xylose have been altered to include xylosyl residues equivalent to the uronic acid determined. Reproduced, by permission, from Phytochemistry.)...

Figure 5.2 Selected sugars and aromatic or aliphatic acids that commonly occur in anthocyanin structures. Sophorose = 2-O-b-D-glucopyranosyl-D-glucose rutinose = 6-O-L-rhamnosyl-D-glucose sambubiose = P-D-xylosyl-(l 2)-P-D-glucose.

Also a-linked xylosides have been synthesized. For example, al,3-linked xylosyl disaccharides were obtained from Xyla/>NP (donor) and glucose or Glcf)pNP (acceptor) in 10-18% yield using an a-xylosidase from archaeon Sulfolobus solfataricus... 

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