a2-Macroglobulin (a2-M) is a large proteinase inhibitor molecule of 718kD, consisting of 4 identical subunits of 185kD each. Produced in hepatocytes and macrophages, plasma concentrations of a2-M are typically 2uM in adults, and as high as 6uM in childhood. a2-M has the ability to inhibit most enzymes from the serine, metallo, cysteine and aspartate subclasses. It is not a member of the Serpin family of inhibitors. It belongs to a class of proteins that include pregnancy zone protein (PZP) and the complement proteins C3, C4 and C5. These proteins contain regions of conserved sequence as well as one or more internal b-cysteinyl-g-glutamyl thiolester bonds. In the case of a2-M are susceptible to cleavage by enzymes or by nucleophilic compounds such as methylamine or ammonium ions. Although the precise nature of the interactions is as yet unknown, it is generally thought that cleavage of a bait region within the a-2M molecule by an enzyme leads to a conformational change, which then traps and/or covalently binds the enzyme. The active site of the trapped enzyme is usually still intact and able to cleave small substrates, but is inaccessible to larger natural substrates. The conformational change induced also exposes receptor-binding regions within the molecule, which may be important in the clearance of a2-M-enzyme complexes from the circulation. It is thought that the main role of a2-M in vivo is that of a ''backup inhibitor and scavenger of proteinases in blood and in tissues. It has also been reported to participate in other physiological processes, including regulation of immune function. Applications: Suitable for use in ELISA and Immunoelectrophoresis. Other applications not tested. Recommended Dilutions: Optimal dilutions to be determined by the researcher. Extinction Coefficient: E1% 280 = 13.4 Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 12 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
Purity:
Purified by immunoaffinity chromatography
Form:
Supplied as a liquid in 10mM HEPES, pH 7.4, 150mM sodium chloride, 50% glycerol
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