Legume

Twenty different legume species (20 genera) were examined for alpha-galactosidase and hemagglutinin activities. Although all of the species contained enzyme activity, only 13 of 20 contained hemagglutinin activities and none displayed a hemagglutinin activity comparable to the previously described alpha-galactosidase-hemagglutinins.The alpha-galactosidase activities in the 20 species possessed remarkably similar kinetic behavior and carbohydrate specificities. All were inhibited by galactose, xylose, and inositol (very similar K(i) values from plant to plant) and had very similar K(m) values for the substrate, p-nitrophenyl alpha-galactoside.Gel filtration analysis of extracts from nine species suggests that legume alpha-galactosidase activities may frequently reside in two molecular weight forms. However, all these species contained a large molecular weight enzyme activity with a size comparable to the alpha-galactosidase-hemagglutinins.Immunochemical studies reveal that the alpha-galactosidases in these plants are immunologically related to an alpha-galactosidase-hemagglutinin and, therefore, are related to one another.These studies suggest that each of the legume species studied (and perhaps all members of this plant family) contain a homologue from a specific class of alpha-galactosidase. Although the previously described alpha-galactosidase-hemagglutinins appear to be members from this enzyme class, these proteins most frequently occur as forms devoid of hemagglutinin activity.