Mediates the efflux of short-chain diamines when energized by an electrochemical gradient (PubMed:31416917). Recognizes specifically the short-chain diamines cadaverine and putrescine as substrates, and promotes the active transport of these substrates in exchange for a cation (PubMed:31416917). Protons are probably the primary source of energy for transport, however it was not possible to conclude with complete certainty that protons, rather than alternative cations such as Na(+) ions, are exchanged for substrates by AceI (PubMed:31416917). In addition, is involved in resistance to the synthetic biocide chlorhexidine, a widely used antiseptic and disinfectant in both hospital and community settings (PubMed:24277845, PubMed:25670776). Interacts directly with chlorhexidine and mediates its efflux via an energy-dependent mechanism (PubMed:24277845). Protonation/deprotonation of Glu-15 may play an important role in transporter function (PubMed:32636271). Cadaverin transport is inhibited in the presence of CCCP (PubMed:31416917). Exists in a monomer-homodimer equilibrium. The dimer is probably the functional form of the protein, and the assembly of the dimer is mediated by binding of chlorhexidine and promoted by high pH conditions. Transcriptionally regulated by the AceR regulator (PubMed:29481596, PubMed:32636271). Strongly induced by the short-chain diamines cadaverine and putrescine. Only moderately induced by the triamine spermidine and weakly induced by the tetraamine spermine (PubMed:31416917). Expression is also induced by more than 10-fold in response to chlorhexidine exposure (PubMed:24277845, PubMed:29481596). Inactivation of the gene results in at least 8-fold reduction in tolerance to cadaverine and putrescine but no change in tolerance to spermidine or spermine (PubMed:31416917). Deletion mutant also shows decreased chlorhexidine resistance (PubMed:29481596). Belongs to the proteobacterial antimicrobial compound efflux (PACE) (TC 2.A.117) family. Extended N-terminus.