SERPINA1 (also known as Alpha 1 Antitrypsin) is an inhibitor of serine proteases that primarily targets elastase but also has a moderate affinity for plasmin and thrombin. Its major physiological function is the protection of the lower respiratory tract against proteolytic destruction by human leukocyte elastase (HLE). The aberrant form of SERPINA1 inhibits insulin-induced NO synthesis in platelets, decreases coagulation time and has proteolytic activity against insulin and plasmin. SERPINA1 is a secreted protein, and in immunohistochemistry it has plasma and extracellular matrix positivity in most tissues throughout the body. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804