Proprotein convertase subtilisin/kexin type 9, also known as PCSK9, is an enzyme that in humans is encoded by the PCSK9 gene. This gene encodes a proprotein convertase belonging to the proteinase K subfamily of the secretory subtilase family. By genomic sequence analysis, the PCSK9 gene was mapped to chromosome 1p32. This protein plays a major regulatory role in cholesterol homeostasis. PCSK9 binds to the epidermal growth factor-like repeat A(EGF-A) domain of the low-absorbance lipoprotein receptor(LDLR), inducing LDLR degradation. Reduced LDLR levels result in decreased metabolism of low-absorbance lipoproteins(LDL), which could lead to hypercholesterolemia. PCSK9 may also have a role in the differentiation of cortical neurons.
