Involved in the succinylase branch of the L-lysine biosynthesis and in the biosynthesis of the pentapeptide incorporated in the peptidoglycan moiety (PubMed:3283102). Catalyzes the stereoinversion of LL-2,6-diaminoheptanedioate (L,L-DAP) to meso-diaminoheptanedioate (meso-DAP) (PubMed:6378903, PubMed:3031013, PubMed:3042781). (2S,6S)-2,6-diaminoheptanedioate = meso-2,6-diaminoheptanedioate Inhibited by 2-(4-amino-4-carboxybutyl)aziri-dine-2-carboxylate (aziDAP) and iodoacetamide. Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; DL-2,6-diaminopimelate from LL-2,6-diaminopimelate: step 1/1. Homodimer. Cells lacking this gene show an unusual large LL-diaminopimelic acid (LL-DAP) pool and an important variations of the LL-DAP/meso-DAP ratio incorporated in the peptidoglycan. DapF utilizes a two-base mechanism involving a pair of cysteine residues (Cys-73 and Cys-217). Belongs to the diaminopimelate epimerase family. Extended N-terminus. Extended N-terminus.