Involved in cell wall peptidoglycan recycling (PubMed:19309146). Specifically cleaves the amide bond between the lactyl group of N-acetylmuramic acid and the alpha-amino group of the L-alanine in degradation products containing an anhydro N-acetylmuramyl moiety (PubMed:19309146). Is also involved in beta-lactamase induction (PubMed:2691840, PubMed:2607970). Hydrolyzes the link between N-acetylmuramoyl residues and L-amino acid residues in certain cell-wall glycopeptides. Zn(2+) is required for amidase activity. kcat is 0.4 sec(-1). Inactivation of AmpD results in AmpR-dependent hyperinduction and AmpD affects beta-lactam susceptibility in the absence of cloned C.freundii amp genes suggesting a linkage between AmpD and peptidoglycan synthesis. Belongs to the N-acetylmuramoyl-L-alanine amidase 2 family.