PFKM and neoplasm: By exploiting the chemoenzymatic approach using UDP-GalNAz and mutant GalT1 combined with CuAAC reaction, Hsieh-Wilson et al. discovered that phosphofructokinase 1 (PFK1), a major regulatory enzyme that controls glucose flux through glycolysis [68], was O-GlcNAcylated at the S529 site under tumor growth conditions [69].