Specifically catalyzes the decarboxylation of meso-diaminopimelate (meso-DAP) to L-lysine. H(+) + meso-2,6-diaminoheptanedioate = CO2 + L-lysine kcat is 939 min(-1). Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; L-lysine from DL-2,6-diaminopimelate: step 1/1. Homodimer. May adopt an induced-fit catalytic mechanism, in which the active site loop (residues 137-155) cycles through down and up conformations to stabilize catalytic intermediates and release reaction products, respectively. Belongs to the Orn/Lys/Arg decarboxylase class-II family. LysA subfamily.