Catalyzes the conversion of N-acetyl-diaminopimelate to diaminopimelate and acetate. H2O + N-acetyl-(2S,6S)-2,6-diaminoheptanedioate = (2S,6S)-2,6-diaminoheptanedioate + acetate Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; LL-2,6-diaminopimelate from (S)-tetrahydrodipicolinate (acetylase route): step 3/3. Belongs to the peptidase M20A family. N-acetyldiaminopimelate deacetylase subfamily. Extended N-terminus.