-!- Protects Enterococcus faecium from the antibiotic vancomycin, which can bind to the -D-Ala-D-Ala sequence at the C-terminus of the peptidoglycan pentapeptide. -!- Reduces the availability of the free dipeptide D-Ala-D-Ala, which is the precursor for this pentapeptide sequence, allowing D-Ala-(R)- lactate (for which vancomycin has much less affinity) to be added to the cell wall instead. -!- The enzyme is stereospecific, as L-Ala-L-Ala, D-Ala-L-Ala and L-Ala- D-Ala are not substrates. -!- Belongs to peptidase family M15.