PURIFICATION AND PROPERTIES OF RAT ALPHA-2 ACUTE-PHASE MACROGLOBULIN

α2 acute-phase macroglobulin was isolated from plasma of turpentine-injected rats. In the method conditions known to damage the biological activities of α2 macroglobulin are avoided. The procedure successively involves: rivanol precipitation, concanavalin A-Sepharose chromatography and ion-exchange chromatography on DEAE-cellulose. Proteolytic activities were minimized throughout the purification. Thus α2 macroglobulin was obatined in a 20% yield and was pure by biochemical and immunological criteria. Its molecular weight appeared to be 760 000 and it consisted of four subunits (Mr 190 000). The protein has an A1 cm1% = 8.8 and an isoelectric point = 4.8. The amino acid and carbohydrate compositions were determined. Our preparations bound 1 molecule of trypsin or 1 molecule of plasmin/molecule of α2 macroglobulin. Kinetic parameters for α2 macroglobulin-bound trypsin and plasmin were determined and compared with those of free trypsin and plasmin using butoxycarbonyl-l-valylglycyl-l-arginine-2-naphthylamide and benzoyl-l-arginine ethylester as substrates. © 1979.