Sambucus nigra Lectin (SNA/EBL I) is an isolectin isolated from elderberry bark and purified by affinity chromatography. SNA I belongs to the group of type 2 ribosome-inactivating proteins and is composed of an A-chain with enzymatic activity and a B-chain with carbohydrate-binding activity. It has specificity for α2,6-linked sialic acid residues, and elutes with the sugar lactose. SNA I can induce apoptosis through the caspase-dependent pathway at low concentrations. This effect depends on the carbohydrate binding of the B-chain and is independent from the catalytic activity of the A-chain.
Alkaline phosphatase (AP) is conjugated to Sambucus nigra Lectin (SNA/EBL I) to show the binding of SNA/EBL 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.