Alpha 2-macroglobulin
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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| Identifiers | |
| Symbol | A2M |
| Entrez | 2 |
| HUGO | 7 |
| OMIM | 103950 |
| RefSeq | NM_000014 |
| UniProt | P01023 |
| Other data | |
| Locus | Chr. 12 p13.31 |
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
Alpha-2 macroglobulin is compose of four identical subunits bound together by -S-S- bonds.
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
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
- ↑ Blacker D, Wilcox MA, Laird NM, et al. (1998). "Alpha-2 macroglobulin is genetically associated with Alzheimer disease". Nat Genet 19 (4): 357–60. PMID 9697696.
- ↑ Kovacs DM (2000). "alpha2-macroglobulin in late-onset Alzheimer's disease". Exp Gerontol 35 (4): 473–9. PMID 10959035.
External links
Globulins: alpha globulins |
|---|
| Alpha 1-antichymotrypsin - Alpha 1-antitrypsin - Alpha 2-macroglobulin - Alpha 2-antiplasmin - Antithrombin - Ceruloplasmin - Haptoglobin - Heparin cofactor II - Orosomucoid - Retinol binding protein - Transcortin |
Acute phase proteins |
|---|
| Alpha 1-antichymotrypsin - Alpha 1-antitrypsin - Alpha 2-macroglobulin - C-reactive protein - Ceruloplasmin - C3 - Fibrin - Haptoglobin - Haemopexin - Orosomucoid - Serum albumin (negative) - Amyloid (P, A) - Transferrin |
Proteins: coagulation | |
|---|---|
| Coagulation factors | intrinsic pathway (FXII, FXI, FIX, FVIII) - extrinsic pathway (Tissue factor, FVII) - common pathway (FX, FV, (Pro)thrombin / FII, Fibrin / FI, FXIII) - HMWK - vWF - Kallikrein |
| Inhibitors | Antithrombin - Protein C - Protein S - Protein Z - ZPI - TFPI |
| Fibrinolysis | Plasmin - tPA/urokinase - PAI-1/2 - α2-AP - α2-macroglobulin - TAFI |
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