The function of PEX39 (peroxisomal biogenesis factor 39, ENSG00000221821) is as follows. Cytosolic peroxin that promotes the peroxisomal import of proteins containing a type-2 peroxisomal targeting signal (PTS2) by binding to PEX7 and stabilizing its interaction with PTS2-containing cargo (PubMed:37160800, PubMed:40739340). PEX39 subsequently transfers the PEX7-cargo complex to PEX13 at the peroxisomal membrane, enabling PEX7 to bind PEX13 and facilitating translocation of PTS2-containing proteins into the peroxisome. Both PEX39 and PEX13 contain a conserved KPWE motif, which enables competitive binding to PEX7 and ensures efficient handover of the complex (PubMed:40739340). .