ACT is a member of the serine proteinase inhibitor (serpin) family that inhibits neutrophilic proteinases – chymotrypsin, cathepsin G, chymases from mast cells, and elastase – protecting tissue from damage by these proteolytic enzymes. ACT is a glycoprotein found in alpha(1)-globulin region in human serum. Alpha 1-antichymotrypsin contains a reactive centre loop that interacts with cognate proteinases, resulting in loop cleavage and a major conformational change.
As an acute phase protein, ACT is active in the control of immune and inflammatory responses, and acts as a tumor marker. ACT inhibits CTL-mediated lysis (CML).
ACT has been identified as a major constituent of the neurofibrillary plaques associated with Alzheimers disease, where it probably enhances the rate of amyloid-fibril formation. Genetic data also suggests that alpha 1-antichymotrypsin is important in the pathogenesis of Alzheimer's disease.[s]
tags [Proteins] [alpha-1 antichymotrypsin] [inflammation] [cytokine] [serine protease inhibitor] [Alzheimers]