anti-α2-Macroglobulin, mAb (2D9)

α2-Macroglobulin (α2M), is a 720-kDa homotetrameric glycoprotein composed of four identical 180 kDa subunit. α2M shares with other α-macroglobulins, like the complement components C3 and C4 and the pregnancy zone protein PZP, an extraordinary binding capacity for a variety of ligands. This allows the α-macroglobulins to serve as humoral defense barriers against foreign peptides in the plasma. α2M interacts and captures virtually any proteinase, often referred to as a panprotease inhibitor. In the brain of Alzheimer's disease (AD) patients, α2M also has been localized to diffuse amyloid plaques, supporting an important role for α2M in AD etiopathology. 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.