The product of this enzyme,?D-alanyl-D-serine, can be incorporated into the peptidoglycan pentapeptide instead of the usual?D-alanyl-D-alanine dipeptide, which is formed by EC?6.3.2.4,?D-alanine¡ªD-alanine ligase. The resulting peptidoglycan does not bind the glycopeptide antibiotics vancomycin and teicoplanin, conferring resistance on the bacteria.