Description
Alpha 1 Antitrypsin (α1AT), also known as Alpha 1Proteinase inhibitor (α1PI), is the most abundant protease inhibitor in blood and a member of the SERPIN family of proteinase inhibitors. Serum levels are typically 1.3 mg/ml (25 µM) but α1AT is an acute phase protein and concentrations can rise four-fold during inflammatory episodes or tissue injury. Low levels in circulation have been associated with pulmonary disease such as emphysema. α1AT is a single chain molecule with a mass of 52,000 daltons that is produced primarily in the liver and to a lesser extent by blood monocytes and intestinal epithelium. Based on association rates, the primary target enzyme for α1AT is believed to be neutrophil elastase, but α1AT is a broad-spectrum inhibitor for many serine proteinases and the main role of α1AT in vivo is likely that of a "backup"inhibitor and proteinase scavenger in fluids and tissues. Although the association rates of α1AT with other enzymes are lower, the high concentration in plasma makes it an important inhibitor of activated Protein C, activated F.XI, thrombin and plasmin. Enzyme inhibition by α1AT occurs through proteolytic cleavage between Met358 and Ser359, which induces a conformational change in α1AT locking the enzyme into a stable, inactive 1:1 enzyme-inhibitor complex