Purification and properties of normal human alpha 1-antitrypsin

A relatively gentle purification method has been devised for the major serine-protease inhibitor in human plasma. The product, a single chain glycoprotein of 50,000 molecular weight, is obtained in 25% yield. It contains 11.5% carbohydrate by weight, a single residue of cysteine and two of tryptophan. N-terminal glutamate or glutamine was found by dansylation. Isoelectric focusing at high resolution in acrylamide gels revealed three major and several minor protein species. Several possible mechanisms to account for this isoelectric microheterogeneity are discussed.