Peroxisomes lack DNA and cannot encode their enzymes. Peroxisomal proteins are synthesized in the ER or the cytosol and imported by peroxins, a group comprising matrix proteins, cytosolic receptors, and membrane proteins. Peroxisomal receptors recognize the proteins by short import sequences at their C- or N-terminus called Peroxisomal Targeting Sequence or PTS1 and 2. The most common PTS1 sequence is the tripeptide, serine, lysine, and leucine. For example, the PTS1 signal of catalase is first recognized in the cytosol by the Pex5 receptor. Pex5 binds a membrane-bound translocator Pex14 to form a multimeric complex that allows catalase to pass into the peroxisomal matrix. Next, a membrane protein containing Pex2, Pex10, and Pex12, ubiquitinates Pex5. The modified Pex5 is helped by the Pex1-Pex6 ATPase complex to dissociate from the membrane and return to the cytosol. The ubiquitin tag is removed by deubiquitinating enzymes, allowing Pex5 to import another protein.