PZP

PZP is highly expressed in late-pregnancy serum and is similar in structure to alpha-2-macroglobulin. The encoded protein, which acts as a homotetramer, inhibits the activity of all four classes of proteinases. This protein contains cleavage sites for several proteinases. Upon binding of a proteinase, the conformation of this protein changes to trap the proteinase, limiting its activity.

Full Name

PZP, Alpha-2-Macroglobulin Like

Function

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.

Biological Process

Female pregnancy

Cellular Location

Secreted