Functionalized glucose-binding lectin from Globularia alypum: extraction, partial purification and biological activities

In the present study, a new glucose specific lectin isolated from roots of an endemic plant Globularia alypum (designated as GaGBL1) is tested for its immunomodulatory, antihyperglycemic, antibacterial, anti-acetylcholinesterase and antioxidant activities. The obtained lectin was exposed to agglutinate human erythrocytes of ABO blood group system as well as the rabbit erythrocytes. Furthermore, the carbohydrate binding property of lectin was confirmed with the inhibition of HA. The fractions showed hemagglutination activity (HA). GaGBL1 was found to be glucose specific lectin with a purification yield of 557.83 μg/mL. It was isolated from a protein capable of agglutinating only human erythrocytes type O. Moreover, its relative agglutinating activity of 128 UH/mg protein was inhibited only by D-glucose with MIC value of 200mM. Meanwhile, D-galactose, D-lactose, D-fructose, D-mannitol, and D-sucrose did not exert this effect. The pure protein GaGBL1 possessed an immunosuppressor action. Meanwhile, this lectin showed no inhibitory effects neither against bacterial strains nor for acetylcholinesterase enzyme. In addition, the results indicated a negative antioxidant activity. Interestingly, it was seen that regular oral administration of GaGBL1 injected by intraperitoneal route to normoglycemic mice showed highly potent antihyperglycemic effect in comparison with the synthetic drug glibenclamide. These data reveal many interesting biological activities of GaGBL1 and suggest that complementary investigations to explore its immunosuppressive and antidiabetic potentials. Hence, further characterization of this novel lectin and understanding of its mechanism of action will help to broaden its scope of biotechnological, pharmaceutical and agricultural applications.