Plays a role in lysine utilization by acting as a lysine decarboxylase. H(+) + L-lysine = cadaverine + CO2 Optimum pH is 6.2-8.0. Homodecamer; built of five dimers associated in a 5-fold symmetrical double-ring. By RpoS-dependent mechanism on stationary phase on the contrary to the second lysine decarboxylase CadA which is not induced by RpoS. Belongs to the Orn/Lys/Arg decarboxylase class-I family.