D-Ala-D-Ala dipeptidase (also known as D-alanyl-D-alanine dipeptidase vanX; VanX; EC 3.4.13.22) is a Zn2+-dependent enzyme that mediates resistance to the antibiotic vancomycin in Enterococci and other bacteria (both Gram-positive and Gram-negative). It is part of a gene cluster that affects cell-wall biosynthesis. The operon triggers the termination of peptidoglycan precursors by D-Ala-(R)-lactate instead of D-Ala-D-Ala dipeptides. The enzyme is stereospecific, as L-Ala-L-Ala, D-Ala-L-Ala and L-Ala-D-Ala are not substrates. It belongs in the MEROPS peptidase family M15, subfamily D.
Jiyao W et al.(2023). "The conserved domain database in 2023.",