Identification of the asparagine synthase responsible for D-Asp amidation in the Lactococcus lactis peptidoglycan interpeptide crossbridge.

We show that in Lactococcus lactis, the gene asnH encodes the asparagine synthase involved in amidation of D-Asp present in peptidoglycan side chains and crossbridges. The level of D-Asp amidation in peptidoglycan has a strong effect on the sensitivity of bacteria to endogenous autolysins and to the cationic antimicrobials nisin and lysozyme.