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 secretory pathway, with unique restricted distribution in both neuroendocrine and non-neuroendocrine tissues. The precursor protein seems to exist in the reticulum endoplasmic as both a monomer and a dimer-sized complex whereas mature form exists only as a monomer, suggesting that propeptide cleavage affects its tertiary or quaternary structure. Interacts (immature form including the propeptide) with RCN3; probably involved in the maturation and the secretion of PCSK6. High expression in the anterior pituitary and in several brain regions, the atrium, and the ventricle. The propeptide domain acts as an intramolecular chaperone assisting the folding of the zymogen within the endoplasmic reticulum. Belongs to the peptidase S8 family.