Application of precipitating activity of Canavalia lineata DC lectin for isolation of alpha 2-macroglobulin from human plasma.

To isolate alpha 2-macroglobulin from human plasma, complex of Canavalia lineata DC lectin and plasma was used as a starting material. The complex was solubilized with 0.08 M phosphate buffer pH 7.2 containing 0.9% NaCl and 0.02 M alpha-methyl-D-mannoside. The solution was applied onto a Bio gel A-5m column and eluted with solubilizing buffer. Of three peaks, only the second peak contained alpha 2-macroglobulin. After equilibrating with 0.06 M potassium phosphate buffer pH 6.8, the fraction was applied onto a hydroxylapatite column and eluted with the same buffer. The eluate was confirmed to be extremely pure alpha 2-macroglobulin; immunoelectrophoresis with anti-human serum produced a single precipitation line, and SDS disc electrophoresis gave a single band at alpha-globulin region. Few differences in carbohydrate composition between this preparation and those prepared by other methods were observed. By this method, about 45% of alpha 2-macroglobulin present in plasma was recovered.