Selectivity for D-lactate incorporation into the peptidoglycan precursors of Lactobacillus plantarum: role of Aad, a VanX-like D-alanyl-D-alanine dipeptidase.
Lactobacillus plantarum produces peptidoglycan precursors ending in D-lactate instead of D-alanine, making the bacterium intrinsically resistant to vancomycin. The ligase Ddl of L. plantarum plays a central role in this specificity by synthesizing D-alanyl-D-lactate depsipeptides that are added to the precursor peptide chain by the enzyme MurF. Here we show that L. plantarum also encodes a D-Ala-D-Ala dipeptidase, Aad, which eliminates D-alanyl-D-alanine dipeptides that are produced by the Ddl ligase, thereby preventing their incorporation into the precursors. Although D-alanine-ended precursors can be incorporated into the cell wall, inactivation of Aad failed to suppress growth defects of L. plantarum mutants deficient in d-lactate-ended precursor synthesis.
Deghorain, M., Goffin, P., Fontaine, L., Mainardi, J.-L., Daniel, R., Errington, J., Hallet, B., & Hols, P. (2007). Selectivity for D-lactate incorporation into the peptidoglycan precursors of Lactobacillus plantarum: role of Aad, a VanX-like D-alanyl-D-alanine dipeptidase. Journal of bacteriology, 189(11), 4332-4337. https://doi.org/10.1128/JB.01829-06 (Original work published 2007)