Furin, also known as paired basic Amino acid Cleaving Enzyme (PACE) is a ubiquitous subtilisin-like proprotein convertase with a minimal cleavage site of Arg-X-X-Arg˅. However, the enzyme prefers the site Arg-X-Lys/Arg-Arg˅. It is the major processing enzyme of the secretory pathway and is localized in the trans-golgi network where it functions to cleave other proteins into their mature/active forms. Substrates of Furin include blood clotting factors, serum proteins and growth factor receptors such as the insulin-like growth factor receptor but also viral proteins like the SARS-CoV-2 Spike protein. Furin is inhibited by EGTA, α1- Antitrypsin Portland and polyarginine compounds.
