(2S,6S)-2,6-diaminoheptanedioate = meso-2,6-diaminoheptanedioate Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; DL-2,6-diaminopimelate from LL-2,6-diaminopimelate: step 1/1. Belongs to the diaminopimelate epimerase family.