Specifically catalyzes the decarboxylation of meso-diaminopimelate (meso-DAP) to L-lysine. H(+) + meso-2,6-diaminoheptanedioate = CO2 + L-lysine Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; L-lysine from DL-2,6-diaminopimelate: step 1/1. Homodimer. Belongs to the Orn/Lys/Arg decarboxylase class-II family. LysA subfamily. Extended N-terminus.