Structural Investigations on Arabinogalactan-Protein from Wheat, Isolated with Yariv Reagent

For the first time a pure arabinogalactan-protein (AGP) could be isolated from whole grain of wheat (Triticum aestivum L.) by performing a double precipitation with P-glucosyl Yariv reagent. The putative bioactive AGP has been characterized with regard to its polysaccharide and protein parts. Analytical investigations by GLC-MS and C-13 NMR revealed a carbohydrate moiety consisting of a 1,3-Galp backbone, linked in position 6 to short 1,6-Galp-chains, terminating in Araf. In the protein part, a high content of hydroxyproline has been found, probably responsible for linkage between protein and polysaccharide moieties. The molecular mass of AGP has been determined by size exclusion chromatography with laser light scattering detection and found to be 125 kDa. Alkaline hydrolysis of the protein resulted in single carbohydrate moieties with a molecular mass of about 20 kDa, indicating that AGP from whole grain of wheat belongs to the wattle blossom type of AGPs.