Editing Alpha-1 antitrypsin (section)

== Function ==
A1AT is a 52-[[kDa]] [[serpin]] and, in [[medicine]], it is considered the most prominent serpin; the terms ''α1-antitrypsin'' and ''[[protease inhibitor (biology)|protease inhibitor]]'' (''P<sub>i</sub>'') are often used interchangeably.

Most serpins inactivate [[enzyme]]s by binding to them [[covalent]]ly. These enzymes are released locally in relatively low concentrations where they are immediately cleared by proteins such as A1AT. In the [[acute phase protein|acute phase reaction]], a further elevation is required to "limit" the damage caused by activated [[neutrophil granulocyte]]s and their enzyme [[elastase]], which breaks down the [[connective tissue]] fiber [[elastin]].

Besides limiting elastase activity to limit tissue degradation, A1PI also acts to induce locomotion of lymphocytes through tissue including immature T cells through the thymus where immature T cells mature to become immunocompetent T cells that are released into tissue to elevate immune responsiveness.<ref>{{cite journal | vauthors = Lapidot T, Petit I | title = Current understanding of stem cell mobilization: the roles of chemokines, proteolytic enzymes, adhesion molecules, cytokines, and stromal cells | journal = Exp Hematol | volume = 30 | issue = 9 | pages = 973–981 | date = September 2012 | pmid = 12225788 | doi = 10.1016/s0301-472x(02)00883-4 | doi-access = free }}</ref>

Like all [[serine protease inhibitor]]s, A1AT has a characteristic [[secondary structure]] of [[beta sheet]]s and [[alpha helix|alpha helices]]. [[Mutation]]s in these areas can lead to non-functional proteins that can [[polymer]]ise and accumulate in the [[liver]] (infantile hepatic cirrhosis).