. "Catalysis of the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: putrescine(out) + ornithine(in) = putrescine(in) + ornithine(out)." . . . . "putrescine:ornithine antiporter activity" . "putrescine-ornithine antiporter activity" . "putrescine/ornithine antiporter activity" . "putrescine:hydrogen symporter activity" . .