Specifically catalyzes the decarboxylation of meso-diaminopimelate (meso-DAP) to L-lysine (Probable). Is essential for the viability of M.tuberculosis in the host (PubMed:12637582). 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; disulfide-linked. Can also form homotetramer at higher protein concentrations. Strains lacking this gene are lysine auxotrophs. They cannot survive in immunocompromised mice. Was identified as a high-confidence drug target. Belongs to the Orn/Lys/Arg decarboxylase class-II family. LysA subfamily.