EndoS is an endoglycosidase from Streptococcus pyogenes that specifically hydrolyzes N-linked glycans in the Fc-region of native IgG. It specifically deglycosylates the conserved N-glycans on the Fc region of IgG by hydrolyzing the chitobiose core (at the beta -1,4 linkage between the two N-acetylglucosamines) of the N-glycans, cleavage leave one GlcNAc residue remaining attached to the asparagine residue on the peptide backbone.