Study of the interaction of azospirillum lectins with sweet almond β- glucosidase

The surface lectins isolated from the nitrogen-fixing soil bacterium Azospirillum brasilense Sp7 and from its mutant defective in lectin activity, A. brasilense Sp 7.2.3, inhibited the activity of sweet almond β-glucosidase. Enzyme inhibition by the lectins was of the competitive type, with inhibition constants (Ki) of 14±0,2 µg/ml for the A. brasilense Sp7 lectin and 4±0,1 µg/ml for the A. brasilense Sp7.2.3 lectin. Lectin inhibition of the enzymes activity was enhanced in the presence of ethanol and several salts (KCl, NaCl, and CaCl2 for the parent strain, and KCl and NaClfor the mutant strain), which permitted the conclusion that the lectin-enzyme interaction is conditioned by electrostatic and hydrophobic interactions.