Serine endoprotease that processes various proproteins by cleavage at paired basic amino acids, recognizing the RXXX[KR]R consensus motif. Likely functions in the constitutive and regulated secretory pathways. Plays an essential role in pregnancy establishment by proteolytic activation of a number of important factors such as BMP2, CALD1 and alpha-integrins. May be responsible for the maturation of gastrointestinal peptides. May be involved in the cellular proliferation of adrenal cortex via the activation of growth factors. Secreted through the regulated secretory pathway. Type I membrane protein localized to a paranuclear post-Golgi network compartment in communication with early endosomes. Additional isoforms seem to exist. PC5A is expressed in most tissues but is most abundant in the intestine and adrenals. PC5B is expressed in the intestine, adrenals and lung but not in the brain. Weakly expressed throughout the embryo, except in the developing nervous system, the ribs and the liver, but markedly up-regulated at discrete sites during development. At 6.5 dpc, prominent expression observed in differentiated decidua. At 7.5 dpc, intense expression in extraembryonic endoderm, amnion and nascent mesoderm. At 8.5 dpc, abundant expression in somites and yolk sac followed by a confinement to dermamyotome compartment. Between 9.5 dpc and 11.5 dpc, abundant expression in AER (thickened ectodermal cells of limb buds). At 12.5 dpc, expression in the limbs is confined to the condensing mesenchyme surrounding the cartilage. At this stage, strong expression also detected in vertebral and facial cartilage primordia and in the muscle of the tongue. At 16.5 dpc, abundant expression in epithelial cells of the intestinal villi. Isoform A is most abundant at all stages but significant levels of isoform B occur at 12.5 dpc. The propeptide domain acts as an intramolecular chaperone assisting the folding of the zymogen within the endoplasmic reticulum. AC 1 and AC 2 (clusters of acidic amino acids) contain sorting information. AC 1 directs TGN localization and interacts with the TGN sorting protein PACS-1. Belongs to the peptidase S8 family.