Liver. By growth hormone. Reduced during acute inflammation. The reactive center loop (RCL) extends out from the body of the protein and directs binding to the target protease. The protease cleaves the serpin at the reactive site within the RCL, establishing a covalent linkage between the serpin reactive site and the protease. The resulting inactive serpin-protease complex is highly stable (By similarity). Variability within the reactive center loop (RCL) sequences of Serpina3 paralogs may determine target protease specificity. N-glycosylated. The single human alpha1-antichymotrypsin gene (SERPINA3) is represented by a cluster of 6 individual rat paralogs. Belongs to the serpin family. It is uncertain whether Met-1 or Met-11 is the initiator.