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 β‐N‐acetylhexosaminidase (TfHexY470N) and human β4‐galactosyltransferase (β4GalTY284L) yielded complex glycans comprising a chitooligomeric spacer (β1,4GlcNAc)n=0–3 terminated with a β4‐linked β‐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 conjugation 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 (β1,4GlcNAc)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. magnified image