Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Alpha 2-macroglobulin
Introduction
Alpha-2 macroglobulin (abbreviated α2M or A2M) is a large plasma protein found in the blood. It is produced by the liver, and is a major component of the alpha-2 band in protein electrophoresis.
Structure
Structure
Alpha-2 macroglobulin is compose of four identical subunits bound together by -S-S- bonds.
Function
Function
Alpha-2 macroglobulin is able to inactivate an enormous variety of proteinases (including serine-, cysteine-, aspartic– and metalloproteinases).
Alpha-2 macroglobulin has in its structure a 35 aminoacid “bait” region. Proteinases binding and cleaving the bait region become bound to α2M. The proteinase-α2M complex is recognised by macrophage receptors and cleared from the system.
It functions as an inhibitor of coagulation:
Disease
Disease
Alpha-2 macroglobulin levels are increased in nephrotic syndrome, a condition wherein the kidneys start to leak out some of the smaller blood proteins. Because of its size, α2-macroglobulin is retained in the bloodstream. Increased production of all proteins means α2-macroglobulin concentration increases. This increase has little adverse effect on the health, but is used as a diagnostic clue. Longstanding chronic renal failure can lead to amyloid by alpha-2 macroglobulin (see main article: amyloid).
A common variant (29.5%) (polymorphism) of α2-macroglobulin leads to increased risk of Alzheimer’s disease,[1][2] although the mechanism is unknown.
α-2 macroglobulin binds to and removes the active forms of the gelatinase (MMP-2 and MMP-9) from the circulation via scavenger receptors on the phagocytes.
References
References
- ↑ Blacker D, Wilcox MA, Laird NM; et al. (1998). “Alpha-2 macroglobulin is genetically associated with Alzheimer disease”. Nat Genet. 19 (4): 357&ndash, 60. PMID 9697696.
- ↑ Kovacs DM (2000). “alpha2-macroglobulin in late-onset Alzheimer’s disease”. Exp Gerontol. 35 (4): 473&ndash, 9. PMID 10959035.
External links
External links
- alpha+2-Macroglobulin at the US National Library of Medicine Medical Subject Headings (MeSH)
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]