α1-antichymotrypsin (ACT) is an α-globulin glycoprotein th at is a member of the serpin superfamily and is encoded by the SERPINA3 gene in humans. Its expression is higher in prostate cancer than in benign prostatic hyperplasia. The serine protease has been found to be associated with several diseases such as chronic obstructive pulmonary disease (COPD), Parkinson′s disease (PD), Alzheimer′s disease (AD), stroke, cystic fibrosis, cerebral haemorrhage and multiple system atrophy. The encoded protein forms a complex with toxic β-amyloid (Aβ). The gene expression is induced by cytokines. ACT inhibits serine proteases, such as pancreatic chymotrypsin, leukocyte cathepsin G, mast cell chymases, human glandular kallikrein 2, kallikrein 3, and pancreatic cationic elastase. The levels of circulating ACT increases with inflammation. It also has the ability to bind to DNA unlike other serpins.
