LDLR and familial hypercholesterolemia: The PCSK9 enzyme, encoded by the PCSK9 gene situated on chromosome 1 inhumans, plays a key role in the degradation of LDL receptors (LDL-R) [20, 21].Formerly known as NARC-1 (neural apoptosis-regulated convertase-1), this proteinconsists of 692 amino acids with a molecular weight of 72 kDa and was firstelucidated in 2003 within the cerebral tissues of individuals afflicted withfamilial hypercholesterolemia [22].