Members of this family are known or trusted examples of ornithine decarboxylase, all encoded in the immediate vicinity of an ornithine-putrescine antiporter. Decarboxylation of ornithine to putrescine, followed by exchange of a putrescine for a new ornithine, is a proton-motive cycle that can be induced by low pH and protect a bacterium against transient exposure to acidic conditions.
Jiyao W et al.(2023). "The conserved domain database in 2023.",