Griffonia simplicifolia lectin (GSL I) is affinity purified from a woody climbing shrub native to Africa. GSL I is composed of two types of subunits A and B that combine to form tetrameric structures, resulting in five isolectins. This lectin has affinity for terminal α-D-galactosyl residues and terminal N-acetyl-α-D-galactosaminyl residues. The A-rich lectin preferentially agglutinates blood group A erythrocytes and thus appears to be specific for α-N-acetylgalactosamine residues, while the B-rich lectin preferentially agglutinates blood group B cells and is specific for α-galactose residues. This lectin shows specificity for blood group B greater than blood group A1.
GSL I has been reported to bind several glycoproteins including laminin. Since some α-D-galactosyl residues are expressed in endothelial cells of mouse tissues, GSL I can present a highly specific surface of glycosylation pattern in these cells.
Alkaline phosphatase (AP) is conjugated to Griffonia simplicifolia Lectin (GSL I) to show the binding of GSL I 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.