Studies on Lectins from Major Vigna species

Lectins are glycoproteins having ability to bind with carbohydrate moieties non-covalently and reversibly. The present investigation was undertaken to study the specificity of lectins from major Vigna species against trypsinized human and rabbit erythrocytes. Crude extracts of Vigna mungo and Vigna radiata resulted in agglutination of trypsinized human as well as rabbit erythrocytes. The extracts from Vigna unguiculata, Vigna umbellata, and Vigna angularis agglutinated only trypsinized rabbit erythrocytes. Isolation and purification of lectin was carried out from Vigna radiata through ion exchange, gel filtration and affinity chromatography. The lectin was isolated to 192.47 fold purification and 73.14 (HU/mg) specific activity. The purified lectin revealed single symmetric protein peak on affinity chromatography. SDS-PAGE of purified lectin revealed a single sharp band of 25.0kDa. Highest agglutination activity of mung bean lectin (MBL) was observed at pH 5.0 with 98% stability and maintained steadily between pH 6–9. The purified MBL exhibited maximum agglutination at 37°C and considerable loss in agglutination activity at 65°C. D-galactose with a minimum inhibitory concentration of 3.12mM was observed as potent inhibitor of agglutination with mung bean lectin. The results of the study revealed that lectins from major Vigna species fall under the category of D-galactose binding group with strong agglutination specificity with trypsinized rabbit erythrocytes.