Legume

Abstract

Twenty different legume species (20 genera) were examined for α-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 α-galactosidase-hemagglutinins.

The α-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 α-galactoside.

Gel filtration analysis of extracts from nine species suggests that legume α-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 α-galactosidase-hemagglutinins.

Immunochemical studies reveal that the α-galactosidases in these plants are immunologically related to an α-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 α-galactosidase. Although the previously described α-galactosidase-hemagglutinins appear to be members from this enzyme class, these proteins most frequently occur as forms devoid of hemagglutinin activity.