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. The propeptide domain acts as an intramolecular chaperone assisting the folding of the zymogen within the endoplasmic reticulum. Belongs to the peptidase S8 family.