Characterization of the fragments obtained by enzymic and alkaline degradation of rice-bran proteoglycans.

Repeated digestion of the proteoglycan B from rice bran with Pronase and hemicellulase yielded two types of glycopeptides. The first group, obtained from the third enzymic digest, was a type of low molecular-weight glycopeptide and was fractionated into two subfractions by paper electrophoresis. The second group, obtained from the fourth enzymic digest, was a mixture of glycopeptides of relatively high molecular-weight and was fractionated into three subfractions by gel filtration on Sephadex G-75. Alkaline degradation of these glycopeptides or the intact proteoglycan A yielded a sugar-amino acid compound, whose structure was established as O-alpha-L-arabinofuranosyl-hydroxyproline. These results indicate that the carbohydrate-protein linkage of the rice-bran proteoglycan is an O-glycosyl linkage between L-arabinose and hydroxyproline.