Two-Step Enzymatic Synthesis of β-D-N-Acetylgalactosamine-(1→4)-D-N-acetylglucosamine (LacdiNAc) Chitooligomers for Deciphering Galectin Binding Behavior

A two-step synthesis of engineered variants of Talaromyces flavus beta-N-acetylhexosaminidase(TfHexY470N) and human beta 4-galactosyltransferase (beta 4GalTY284L) yielded complex glycans comprising a chitooligomeric spacer (beta 1,4GlcNAc) (n= 0-3) terminated with a beta 4-linked beta-D-N-acetylgalactosamine-(1 -> 4)-D-N-acetylglucosamine (LacdiNAc) epitope. These compounds are novel inhibitors of human galectin-3 (Gal-3), a widely spread animal lectin with important physiological functions in cellular communication. The multivalent presentation of glycan oligomers was accomplished by chemical con-jugation of glycans to lysine residues of bovine serum albumin (BSA). Binding studies of Gal-3 to immobilized BSA neo-glycoconjugates revealed the beneficial influence of the chitooligomeric spacer for the ligand-lectin affinity. We conclude that the use of the beta 1,4GlcNAc) (n= 0-3) spacer is a perfect nature-like solution for the presentation of elaborated Gal-3 glycan epitopes that surpasses the performance of commonly used synthetic spacers.