Under acidic conditions, in the presence of lysine, functions as a cadaverine:lysine antiporter that facilitates the excretion of cadaverine and the uptake of lysine. At neutral pH, also catalyzes the uptake of cadaverine via a proton symport mechanism, however the physiological relevance of this uptake activity is probably negligible because the expression of cadB is low at neutral pH. Cadaverine uptake activity is low at acidic pH