Isolation and Some Properties of a New Enzyme-Binding Protein in Rat Plasma

Abstract

.alpha.1-Inhibitor3 (.alpha.-I3), a new enzyme-binding protein, was isolated from rat plasma by a combination of ammonium sulfate precipitation, ion exchange chromatography on DEAE cellulose and gel filtration on ultrogel AcA34. Agarose gel electrophoresis of the purified inhibitor showed a single protein band with .alpha.1-mobility giving a single precipitation line on immunoelectrophoresis against anti-rat serum. A specific antiserum against the purified inhibitor was raised in rabbits. .alpha.1-I3 showed immunologic cross-reaction with human inter-.alpha.-trypsin inhibitor. .alpha.1-I3 formed a complex with trypsin, which was thereby inhibited. The electrophoretic mobility of the complex was less than that of the free inhibitor. Inflammation, induced by turpentine, caused a decrease in the serum concentration of .alpha.1-I3 to 36% of the initial value within 48 h. .alpha.2 Acute phase macroglobulin (.alpha.2-AP) showed a simultaneous increase to 7.1 g/l and .alpha.1-antitrypsin (.alpha.1-AT) to twice its normal value.