Is able to inhibit all four classes of proteinases by a unique 'trapping' mechanism. This protein has a peptide stretch, called the 'bait region' which contains specific cleavage sites for different proteinases. When a proteinase cleaves the bait region, a conformational change is induced in the protein which traps the proteinase. The entrapped enzyme remains active against low molecular weight substrates (activity against high molecular weight substrates is greatly reduced). Following cleavage in the bait region, a thioester bond is hydrolyzed and mediates the covalent binding of the protein to the proteinase.

Secreted.

Protease inhibitor I39 (alpha-2-macroglobulin) family

Highest expression in liver, medium expression in ovary, heart and stomach. Low expression in lung, kidney and uterus. Protein found in plasma.

STRING: 10090.ENSMUSP00000107760

UniGene: Mm.260144