α2-Macroglobulin
Biochemistry
| Molecular mass | 725.000 Da | |
|---|---|---|
| Synthesis | Liver | |
| Half-Life | 2 - 3 days | |
| Serum Concentration | 11 days - 18 years 19 years - 25 years 26 years - 61 years | 2.7 - 5.4 g/l 1.8 - 16 U/ml 1.4 - 4.1 g/l 1.4 -12 U/ml 1.4 - 2.8 g/l 1.4 - 4.8 U/ml |
| Normal range | Activity | 0.7 - 1.50 U/ml |
As a very unspecific inhibitor, α2-macroglobulin inhibits proteases of all classes, including a variety of coagulation enzymes, such as thrombin, plasmin and kallikrein. The inhibitory activity is achieved by a so-called ‚bait region’ in the α2-macroglobulin molecule that is cleaved by the proteases. This results in a conformational change that captures the proteases in a type of cage. As α2-macroglobulin is the most important inhibitor of coagulation in new-borns, the plasma level is relatively high compared to adults.
Clinical significance
Reduced plasma concentrations have been observed during fibrinolytic therapy and in hyperfibrinolysis. Increased concentrations are observed during pregnancy, in women taking oral contraceptives, in the nephrotic syndrome, in diabetes mellitus and as a consequence of liver disease. Increased α2-macroglobulin concentrations in adults are of no clinical significance.
Indication
Control of plasma concentration in new-borns and small children, as α2-macroglobulin is the most important inhibitor of coagulation at this age.
Literature
- Friberger P. Chromogenic peptide substrates. Their use for the assay of factors in the fibrinolytic and plasma kallikrein-kinin systems. Scand J Clin Lab Invest 42, Suppl 162, 84-85, 1982.
- Gallimore MJ, Aurell L, Friberger P & Gustavsson S. Chromogenic peptide substrate assays for determining functional activities of α2-macroglobulin and α1-antitrypsin using a new trypsin substrate. Thromb Haemost 50, 230, 1983.
- Velasco F, Torres A, Guerrero A, Andres P, Guerrero R, Aljama P, Alvarez F. Behaviour of the contact phase of blood coagulation in the adult respiratory distress syndrome (ARDS). Thromb Haemost 55, 357-360, 1986.
- Martinez-Brotons F, Oncins JR, Mestres J, Amargos V & Reynaldo C. Plasma kallikrein-kinin system in patients with uncomplicated sepsis and septic shock - Comparison with cardiogenic shock. Thromb Haemost 58, 709-713, 1987.
- Persson L et al. Tobacco smoking and neutrophil activity in patients with periodontal disease. J Periodontol 72, 90-5, 2001.