(A) Structure of O -acetylpeptidoglycan and (B) reaction pathway of lytic transglycosylases (LT). A. The O-acetylation of peptidoglycan occurs at the C-6 hydroxyl group of MurNAc residues (shown in red) to generate the corresponding 2-N-6-O-diacetylmuramyl residue (OAcMurNAc). B. The lytic transglycosylases (LT) require a free C-6 hydroxyl group to catalyze the formation of 1,6-anhdyroMurNAc products. The R denotes the stem peptide associated with the C-3 lactyl moiety of MurNAc residues.