PCSK9 is a proprotein convertase belonging to the proteinase K subfamily of the secretory subtilase family. PCSK9 is synthesized as a soluble zymogen that undergoes autocatalytic intramolecular processing in the endoplasmic reticulum. PCSK9 may function as a proprotein convertase. PCSK9 plays a role in cholesterol homeostasis and may have a role in the differentiation of cortical neurons. Mutations in PCSK9 gene have been associated with a third form of autosomal dominant familial hypercholesterolemia.Synonyms: NARC-1, NARC1, Neural apoptosis-regulated convertase 1, PCSK-9, Proprotein convertase PC9, Proprotein convertase subtilisin/kexin type 9, Subtilisin/kexin-like protease PC9