Kallistatin is a serine proteinase inhibitor (serpin) and a heparin-binding protein. It is localized in vascular smooth muscle cells and endothelial cells of blood vessels, suggesting that it may be involved in the regulation of vascular function.The 1,284-bp cDNA encodes 427 amino acid residues, including a 26-residue signal peptide and a 401-residue mature peptide. The translated amino acid sequence of kallistatin matches the protein sequence and shares 44 to 46% sequence identity with human alpha-1-antichymotrypsin (AACT), alpha-1-antitrypsin (PI), corticosteroid-binding globulin (CBG), thyroxine-binding globulin of serum (TBG), and protein C inhibitor (PCI). All of these except TBG, which is encoded by the X chromosome, are encoded by genes on chromosome 14.