Binding profile of Artocarpus integrifolia agglutinin (Jacalin)

Artocarpus integrifolia agglutinin (Jacalin) from the seeds of jack fruits has attracted considerable attention for its diverse biological activities and has been recognized as a Galβ1→3GalNAc (T) specific lectin. In previous studies, the information of its binding was limited to the inhibition results of monosaccharides and several T related disaccharides, but its interaction with other carbohydrate structural units occurring in natural glycans has not been characterized. For this reason, the binding profile of this lectin was studied by enzyme linked lectinosorbent assay (ELLSA) with our glycan/ligand collection. Among glycoproteins (gps) tested for binding, high density of multi-Galβ1→3GalNAcα1→ (mT_α) and GalNAcα1→Ser/Thr (mTn) containing gps reacted most avidly with Jacalin. As inhibitors expressed as nanograms yielding 50% inhibition, these mT_α and mTn containing glycans were about 7.1 × 10³, 4.0 × 10⁵, and 7.8 × 10⁵ times more potent than monomeric T_α, GalNAc, and Gal. Of the sugars tested and expressed as nanomoles for 50% inhibition, Tn containing peptides, T_α, and the human P blood group active disaccharide (P_α, GalNAcβ1→3Galα1→) were the best and about 283 times more active than Gal. We conclude that the most potent ligands for this lectin are mTn, mT, and possibly P_α glycotopes, while GalNAcβ1→4Galβ1→, GalNAcα1→3Gal, GalNAcα1→3GalNAc, and Galα1→3Gal determinants were poor inhibitors. Thus, the overall binding profile of Jacalin can be defined in decreasing order as high density of mTn, and mT_α ⋙ simple Tn cluster > monomeric T_α > monomeric P_α > monomeric Tn > monomeric T > GalNAc > Gal > Methylα1→Man ≫ Man and Glc (inactive). Our finding should aid in the selection of this lectin for biological applications.