Specifically hydrolyzes gamma-D-glutamyl-L-lysine bonds in murein peptides, releasing L-Ala-D-Glu. The enzyme releases L-Ala-gamma-D-Glu dipeptides from cell wall peptides via cleavage of an L-Ala-gamma-D-Glu-|-L-Lys bond. Cell wall degradation; peptidoglycan degradation. Monomer in solution. Belongs to the peptidase C40 family.