α-Galactosidase from Vicia faba seeds has been resolved into three molecular forms, I, II1 and II2, respectively. Enzyme I is a tetramer (M r 160 000) consisting of identical sub-units (M r 44000 ± 2000). All three forms display lectin activity with glucose/mannose specificity. Enzyme I has been further studied with respect to its lectin specificity and various factors affecting this property. The results indicate that the catalytic and the lectin sites reside in the same protein molecule. The results presented are unique in that the enzyme activity is specific for galactose and its lectin activity is specific for glucose/mannose.
