线性范围：0.1ng/ml-6ng/ml.Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme encoded by the PCSK9 gene in humans on chromosome 1. It is the 9th member of the proprotein convertase family of proteins that activate other proteins. PCSK9 is ubiquitously expressed in many tissues and cell types. PCSK9 binds to the receptor for low-density lipoprotein particles (LDL), which typically transport 3,000 to 6,000 fat molecules (including cholesterol) per particle, within extracellular fluid. The LDL receptor (LDLR), on liver and other cell membranes, binds and initiates ingestion of LDL-particles from extracellular fluid into cells, thus reducing LDL particle concentrations. However, when PCSK9 is bound to the LDLR, after the LDLR & LDL particle combination has been ingested, the receptor is degraded and is no longer recycled back to the cell membrane surface to bind and ingest more LDL-particles. If PCSK9 is blocked, more LDLRs are recycled and are present on the surface of cells to remove LDL-particles from the extracellular fluid.Therefore, blocking PCSK9 can lower blood LDL-particle concentrations. Similar genes (orthologs) are found across many species. As with many proteins, PCSK9 is inactive when first synthesized, because a section of peptide chains blocks their activity; proprotein convertases remove that section to activate the enzyme. PCSK9 has medical importance because it acts in lipoprotein homeostasis. Agents which block PCSK9 can lower LDL particle concentrations. The first two PCSK9 inhibitors, alirocumab and evolocumab, were approved as once every two week injections, by the U.S. Food and Drug Administration in 2015 for lowering LDL-particle concentrations when statins and other drugs were not sufficiently effective or poorly tolerated. The cost of these new medications, as of 2015, was $14,000 per year at full retail; judged of unclear cost effectiveness by some.[12] However, as of 2016, many commercial payers, after considerable prescribing physician work answering questions, will cover these medications for copays of $10 per month. The PCSK9 gene also contains one of 27 loci associated with increased risk of coronary artery disease