A murein DD-endopeptidase with specificity for D-Ala-meso-diaminopimelic acid (mDAP) cross-links. Its role is probably to cleave D-Ala-mDAP cross-links to allow insertion of new glycans and thus cell wall expansion. Functionally redundant with MepM and MepH. Also has weak LD-carboxypeptidase activity on L-mDAP-D-Ala peptide bonds (By similarity). 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; cell wall polysaccharide biosynthesis. Monomer. Belongs to the peptidase C40 family.