Identification and biological activity of lectins of different subunit composition isolated from Phaseolus vulgaris L var athropurpurea

Protein concentrate, albumin (AF) and globulin fractions (GF) (60.2, 42.3 and 69.7% of protein content, N x 5.40, respectively) were obtained from raw seeds of Phaseolus vulgaris var athropurpurea (PHVa) cultivated in northern Spain. SDS-PAGE analysis revealed that the isolectins were present solely in the AF while the GF was entirely lectin-free. Affinity chromatography and SDS-PAGE were used to separate and identify lectins of different subunit composition: E 4 + E 3 L, E 2 L 2 , El 3 and L 4 (in g : 0.12, 0.03, 0.03 and 0.44, respectively, from 2.9 g of PHVa meal). In this cultivar the amount of E 4 was negligible. With the methodology followed in this study the L 4 isolectin could not be isolated from the AF and it was determined by densitometry. The biology activities of these PHVa phytohaemagglutinins-erythroagglutinating and lymphocyte transformation activities-were assessed in rat and human cells. There was a direct correlation between the erythroagglutinating activity and the E subunit composition of the isolectins using rat red blood cells. The lymphocyte transformation activity of the isolectins with human peripheral blood lymphocytes was correlated with the L-subunit content in the lectins. However, the relationship between lymphocyte transformation activity and lectin profile with rat lymphatic node lymphocytes was not as straightforward as expected.