Anti-PCSK8 antibodies are protein reagents that detect specific antigens. The PCSK8 antigen is another term for the human protein membrane bound transcription factor peptidase, site 1, encoded by the MBTPS1 gene. The protein is reported to be a serine protease that cleaves after hydrophobic or small residues, provided that Arg or Lys is in position P4: known substrates include SREBF1/SREBP1, SREBF2/SREBP2, BDNF, GNPTAB, ATF6, ATF6B and FAM20C. Canonically, it has an amino acid length of 1052 residues and a mass of 117.7 kilodaltons. Its subcellular localization is in the ER and Golgi and it is widely expressed across many tissue types. The PCSK8 protein is a member of the Peptidase S8 protein family. Other alias names for PCSK8 include S1P and SEDKF.