Diaminopimelic acid (DAP) is an amino acid, representing an epsilon-carboxy derivative of lysine.
DAP is a characteristic of certain cell walls of some bacteria. DAP is often found in the peptide linkages of NAM-NAG chains that make up the cell wall of gram-negative bacteria. When provided, they exhibit normal growth. When in deficiency, they still grow but with the inability to make new cell wall proteoglycan.