Decarboxylates both L-lysine and L-ornithine with similar catalytic efficiency. H(+) + L-lysine = cadaverine + CO2 H(+) + L-ornithine = CO2 + putrescine Inhibited competitively by both alpha-difluoromethyllysine and alpha-difluoromethylornithine. Amine and polyamine biosynthesis; putrescine biosynthesis via L-ornithine pathway; putrescine from L-ornithine: step 1/1. Homodimer. Mutagen studies showed that it is possible to convert S.ruminantium LDC to an enzyme with a preference for decarboxylating L-ornithine when five amino acid residues (Ala-44, Gly-45, Val-46, Pro-54 and Ser-322) were replaced with the corresponding ones found in mouse ODC. Belongs to the Orn/Lys/Arg decarboxylase class-II family.