Editing Alpha-2-Macroglobulin (section)

{{Short description|Large plasma protein found in the blood}}
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'''α<sub>2</sub>-Macroglobulin''' ('''α<sub>2</sub>M''') or '''alpha-2-macroglobulin''' is a large (720 KDa) [[plasma protein]] found in the [[blood]]. It is mainly produced by the [[liver]], and also locally synthesized by [[macrophages]], [[fibroblasts]], and [[adrenocortical cells]]. In humans it is encoded by the ''A2M'' gene.

α<sub>2</sub>-Macroglobulin acts as an antiprotease and is able to inactivate an enormous variety of proteinases. It functions as an inhibitor of fibrinolysis by inhibiting [[plasmin]] and [[kallikrein]]. It functions as an inhibitor of coagulation by inhibiting [[thrombin]]. α<sub>2</sub>-macroglobulin may act as a carrier protein because it also binds to numerous growth factors and cytokines, such as platelet-derived growth factor, basic fibroblast growth factor, TGF-β, insulin, and IL-1β.

No specific deficiency with associated disease has been recognized, and no disease state is attributed to low concentrations of α<sub>2</sub>-macroglobulin. The concentration of α<sub>2</sub>-macroglobulin rises 10-fold or more in the nephrotic syndrome when other lower molecular weight proteins are lost in the urine. The loss of α<sub>2</sub>-macroglobulin into urine is prevented by its large size. The net result is that α<sub>2</sub>-macroglobulin reaches serum levels equal to or greater than those of albumin in the nephrotic syndrome, which has the effect of maintaining [[oncotic pressure]].