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.


Control of plasma concentration in new-borns and small children, as α2-macroglobulin is the most important inhibitor of coagulation at this age.


  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. Persson L et al. Tobacco smoking and neutrophil activity in patients with periodontal disease. J Periodontol 72, 90-5, 2001.
Test kit
Chromogenic Assay

UNITEST α2-Macroglobulin

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