Concanavalin A-binding glycopeptides from rat brain glycoproteins.

The affinity of concanavalin A for neutral and acidic glycopeptides derived from rat brain glycoproteins was investigated by studying the inhibition of a concanavalin A-glycogen precipitation system. The neutral, mannose-rich glycopeptides obtained by column electrophoresis of the dialyzable glycopeptides that had been solubilized by proteolytic treatment of defatted brain tissue were powerful inhibitors, with an inhibitory activity 20 to 26 times that of the standard inhibitor, methyl-alpha-D-mannoside. The acidic sialoglycopeptides had activities one to nine times that of the mannoside. Therefore, both acid and neutral glycopeptides were capable of interacting with concanavalin A. The especially strong affinity of the neutral mannose-rich glycopeptides, however, enabled their retention on concanavalin A-Sepharose and subsequent elution with methyl-alpha-D-mannoside. This provided the means of separation of the acidic sialoglycopeptides from the neutral, mannose-rich glycopeptides by affinity chromatography. Glycopeptides that contain N-acetylgalactosamine are not retained by concanavalin A-Sepharose.