Plays an essential role in lysine utilization by acting as a lysine decarboxylase. H(+) + L-lysine = cadaverine + CO2 Homodecamer. Transcriptionally regulated by ArgR in response to arginine but not lysine showing a tight connection of lysine catabolism to the arginine regulatory network. Loss of growth on lysine as sole carbon source (PubMed:20833801). Inactivation leads also to a decrease of virulence showing the importance of LdcA involvement in polyamine homeostasis during infection of the host (PubMed:31653338). Belongs to the Orn/Lys/Arg decarboxylase class-I family.