Releases the terminal D-alanine residue from the cytoplasmic disaccharide-tetrapeptide GlcNAc-MurNAc-L-Ala-gamma-D-Glu-meso-Dap-D-Ala, which is a murein turnover product. Probably also act on free tetrapetide. May be involved in murein recycling. H2O + N-acetyl-D-glucosaminyl-N-acetylmuramoyl-L-alanyl-D-glutamyl-6-carboxy-L-lysyl-D-alanine = D-alanine + N-acetyl-D-glucosaminyl-N-acetylmuramoyl-L-alanyl-D-glutamyl-6-carboxy-L-lysyl Cell wall biogenesis; peptidoglycan recycling. Homodimer. Belongs to the peptidase S66 family.