Soybean hemagglutinin, a plant glycoprotein. I. Isolation of a glycopeptide.

1. A procedure is given for the preparation of purified soybean hemagglutinin from untoasted soybean flour. The final purification step involves column chromatography on calcium phosphate. The homogeneity of the purified protein was ascertained chromatographically and electrophoretically. 2. The purified soybean hemagglutinin was found to contain mannose (4.5 %) and glucosamine (1%). 3. The carbohydrate moiety was released from the protein in the form of a glycopeptide on proteolysis of the hemagglutinin with Pronase. After purification on Sephadex and Dowex 50, the glycopeptide was found to contain aspartic acid in addition to essentially all the carbohydrate of soybean hemagglutinin. 4. The molecular weight of the glycopeptide as determined by equilibrium centrifugation (4,600) corresponds to that calculated from its aspartic acid, mannose, and glucosamine content (4,400), assuming a single aspartic acid residue per polysaccharide unit. From the size of the glycopeptide, the molecular weight of the soybean hemagglutinin (1 lO,OOO), and its carbohydrate content it was concluded that the carbohydrate moiety in this glycoprotein is present as a single polysaccharide chain.