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. kcat is 5.7 sec(-1) with L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala as substrate. kcat is 2.6 sec(-1) with L-Ala-gamma-D-Glu-L-Lys-D-Ala as substrate. kcat is 1.2 sec(-1) with L-Ala-gamma-D-Glu-L-Lys as substrate. Cell wall degradation; peptidoglycan degradation. Repressed by AbrB, a transcription factor that negatively controls biofilm formation. Belongs to the peptidase C40 family.