cofactor:Calcium.,disease:Defects in PCSK9 are the cause of familial hypercholesterolemia 3 (FH3) [MIM:603776]. FH3 inheritance is autosomal dominant.,enzyme regulation:Inhibited by EGTA.,function:May be implicated in the differentiation of cortical neurons and may play a role in cholesterol homeostasis.,PTM:The soluble zymogen undergoes autocatalytic intramolecular processing in the endoplasmic reticulum, resulting in the cleavage of its propeptide that remains associated with the secreted enzyme.,similarity:Belongs to the peptidase S8 family.,similarity:Contains 1 peptidase S8 domain.,subunit:The precursor protein but not the mature protein may form multimers.,tissue specificity:Expressed in neuro-epithelioma, colon carcinoma, hepatic and pancreatic cell lines, and in Schwann cells.,