Endohexosaminidase-catalyzed synthesis of glycopeptides and proteins

The synthetic application of endohexosaminidase enzymes (e. g., Endo A, Endo M, Endo D) promises to allow ready access to a wide variety of defined homogeneous glyco proteins and glycopeptides. The use of N-glycan oligosaccharides that are activated at the reducing terminus as oxazolines allows their high-yielding attachment to almost any amino acid, peptide, or protein that contains a GlcNAc residue as an acceptor. A wide variety of oxazoline donors are readily available, either by total synthesis or by isolation of the corresponding oligosaccharide from natural sources and then conversion to the oxazoline in water. The synthetic potential of the enzymes is particularly augmented by the production of mutant glycosynthases, the use of which allows the synthesis of a wide variety of glycopeptides and glycoproteins bearing defined homogeneous N-glycan structures.