Not involved in transpeptidation but exclusively catalyzes a DD-carboxypeptidase and DD-endopeptidase reaction. Preferential cleavage: (Ac)2-L-Lys-D-Ala-|-D-Ala. Also transpeptidation of peptidyl-alanyl moieties that are N-acyl substituents of D-alanine. Cell wall biogenesis; peptidoglycan biosynthesis. In E.coli there are three murein endopeptidases: two are penicillin sensitive (DacB and PbpG), the other (MepA) not. Belongs to the peptidase S13 family.