The effect of periodate oxidation and alpha-mannosidase treatment on Dolichos biflorus lectin

The effects of periodate oxidation and alpha-mannosidase treatment of the Dolichos biflorus lectin were determined. Destruction by periodate of 16% of the mannose residues of the lectin had no effect on its ability to agglutinate type A erythrocytes, precipitate blood group A + H substance or to be precipitated by concanavalin A. Removal of up to 40% of the mannose by either periodate or alpha-mannosidase rendered the lectin nonprecipitable by concanavalin A. The lectin treated by alpha-mannosidase retained its ability to agglutinate erythrocytes and precipitate blood group A + H substance, but the lectin treated with periodate lost most of its activity. The results suggest that the complete integrity of the carbohydrate unit of the lectin is not necessary for its activity and that the periodate may be affecting the protein portion of the molecule as well as its carbohydrate residues. No conversion of form A to form B of the lectin was observed with either periodate oxidation or alpha-mannosidase treatment.