Peptidoglycan endopeptidase that cleaves the bond between D-glutamate and meso-diaminopimelate. Binds and degrades high-molecular weight peptidoglycan. Required for normal separation of daughter cells after cell division and for cell wall integrity (By similarity). Monomer. Localizes to the septa. Expression depends on the two-component regulatory system MtrA/MtrB. Essential, it cannot be disrupted. Depletion experiments show cells grow as long, branched chains that form clumps. Periodic septa and DNA segregation appear to occur normally along the filaments. Has increased susceptibility to carbenicillin, a cell wall-targeted antibiotic. Depletion effects are reversible. Belongs to the peptidase C40 family.