Lectins LI and LII, localized on the surface of the nitrogen-fixing soil bacterium Bacillus polymyxa 1460, were shown to possess proteolytic activity. A relationship was found between the proteolytic and hemagglutinating activities of the lectins. Blocking of hemagglutinating activity with specific carbohydrate haptens led to significant changes in the enzyme activity of both lectins. When lectin activity was blocked with glucuronic acid and fructose-1,6-diphosphate, the proteolytic activity of both LI and LII declined, whereas incubation with D-galactosamine and D-glucosamine promoted increases in the proteolytic activity of LII. This study proposes that the molecules of the B. polymyxa lectins may have two centers on their surfaces: one responsible for lectin activity and the other for proteolytic activity.