FIG. 1.

Activities of endopeptidases and amidases on peptidoglycan subunits. Endopeptidases PBP 4 and PBP 7 cleave cross-linked peptide side chains, while amidases cut the bond connecting the peptide to the NAM component of the polymerized glycan backbone. The figure shows a pentapeptide monomer (upper left) cross-linked (dashed line) to a tetrapeptide monomer (lower right). NAG, N-acetylglucosamine; NAM, N-acetylmuramic acid; l-ala, l-alanine; d-glu, d-glutamic acid; DAP, diaminopimelic acid; d-ala, d-alanine.