Purification and characterization of alpha 1-antitrypsin secreted by recombinant yeast Saccharomyces diastaticus.

The secreted human alpha 1-antitrypsin (alpha 1AT) produced by yeast was purified from the culture medium by ultrafiltration, ammonium sulfate fractionation (60-75% saturation), protamine sulfate treatment, and ion-exchange chromatography. Molecular mass of the purified alpha 1AT was 52 kDa, which is similar to that of human plasma alpha 1AT. Yeast-produced alpha 1AT was fully functional as an inhibitor compared with the plasma form. Unlike plasma alpha 1AT, however, treatment of the yeast-produced alpha 1AT with endoglycosidase H decreased the molecular mass to that of recombinant alpha 1AT produced in Escherichia coli, indicating the high-mannose type N-linked glycosylation of the secreted alpha 1AT. Glycosylation in yeast cells enhanced kinetic stability of alpha 1AT towards heat deactivation.