Peptidoglycan Precursor (Lys-D-Ala-D-Ala) (None)

The peptidoglycan precursor containing the sequence Lys-D-Ala-D-Ala is a peptide motif found in the biosynthetic pathway of bacterial cell wall peptidoglycan. This tripeptide is a critical component of the stem peptide attached to N-acetylmuramic acid in Gram-positive bacteria, where L-lysine replaces meso-diaminopimelic acid (used by many Gram-negative bacteria) as the third amino acid in the chain. The terminal D-Ala-D-Ala dipeptide is essential for cross-linking reactions catalyzed by penicillin-binding proteins (PBPs), which are targeted by β-lactam antibiotics and glycopeptides like vancomycin.

Other names

Ac-Lys-(D-Ala)₂-OHACETYL-LYS-D-ALA-D-ALAN(2)-acetyllysyl-alanyl-alanine

β-lactams mimic the structure of the terminal D-Ala–D-Ala dipeptide, irreversibly acylating PBPs and blocking transpeptidation. Glycopeptides like vancomycin bind non-covalently to this motif, preventing enzyme access required for cross-linking peptidoglycan strands.