Alpha-1 antitrypsin
mammalian protein found in Homo sapiens
Alpha-1 antitrypsin or α1-antitrypsin (A1AT, α1AT, A1A, or AAT) is a protein belonging to the serpin superfamily. It is encoded in humans by the SERPINA1 gene. A protease inhibitor, it is also known as alpha1–proteinase inhibitor (A1PI) or alpha1-antiproteinase (A1AP) because it inhibits various proteases (not just trypsin). As a type of enzyme inhibitor, it protects tissues from enzymes of inflammatory cells, especially neutrophil elastase.
When the blood contains inadequate or defective A1AT (as in alpha-1 antitrypsin deficiency), neutrophil elastase can excessively break down elastin, leading to the loss of elasticity in the lungs. This results in respiratory issues, such as chronic obstructive pulmonary disease, in adults. Normally, A1AT is produced in the liver and enters the systemic circulation. However, defective A1AT may accumulate in the liver, potentially causing cirrhosis in both adults and children.
A1AT not only binds to neutrophil elastase from inflammatory cells but also to elastase on the cell surface. In this latter role, elastase acts as a signaling molecule for cell movement, rather than as an enzyme.
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