Phaseolus limensis agglutinin (LBA) is isolated from lima bean seeds and purified by affinity chromatography. LBA is composed of 30,000 Da subunits, of which two are joined by a disulfide bond. Each subunit contains a cysteine residue which is required for both it’s carbohydrate- and metal-ion-binding activities. It has a carbohydrate specificity of terminal GalNAcα(1,3)Gal that elutes with N-acetylgalactosamine. LBA agglutinates blood group A erythrocytes.
Alkaline phosphatase (AP) is conjugated to Phaseolus limensis Lectin (LBA) to show the binding of LBA in many applications including Western blotting and ELISA. Alkaline phosphatase is a large protein (140 kDa) that catalyzes the hydrolysis of phosphate groups from a substrate resulting in a colored or fluorescent product. The optimal enzymatic activity of this protein is between pH 8 and 10, and its reaction rate remains linear, improving sensitivity over time.