Pancpin (also called proteinase inhibitor 14/PI14 or myoepithelium-derived serine protease inhibitor/MEPI ) is an inhibitory member of the serpin superfamily. It is downregulated in pancreatic and breast cancer, and is associated with acinar cell apoptosis and pancreatic insufficiency when absent in mice. Pancpin was found to inhibit pancreatic chymotrypsin and elastase. It is thought that pancpin protects pancreatic cells from the consequences of premature activation of their respective zymogens. This subgroup belongs to clade I of the serpin superfamily. In general, SERine Proteinase INhibitors (serpins) exhibit conformational polymorphism shifting from native to cleaved, latent, delta, or polymorphic forms. Many serpins, such as antitrypsin and antichymotrypsin, function as serine protease inhibitors which regulate blood coagulation cascades. Non-inhibitory serpins perform many diverse functions such as chaperoning proteins or transporting hormones. Serpins are of medical interest because mutants have been associated with blood clotting disorders, emphysema, cirrhosis, and dementia. A classification based on evolutionary relatedness has resulted in the assignment of serpins to 16 clades designated A-P along with some orphans.
Comment:depending on the conformational state, the RC loop is surface accessible in the active form or buried and inserted as the central beta strand in the inactive form.
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