Isolation and characterization of highly purified alpha-1-antitrypsin

Methods of Purification and Application Procedures of Alpha1 Antitrypsin: A Long-Lasting History

The aim of the present report is to review the literature addressing the methods developed for the purification of alpha1-antitrypsin (AAT) from the 1950s to the present. AAT is a glycoprotein whose main function is to protect tissues from human neutrophil elastase (HNE) and other proteases released by neutrophils during an inflammatory state. The lack of this inhibitor in human serum is responsible for the onset of alpha1-antitrypsin deficiency (AATD), which is a severe genetic disorder that affects lungs in adults and for which there is currently no cure. Being used, under special circumstances, as a medical treatment of AATD in the so-called "replacement" therapy (consisting in the intravenous infusion of the missing protein), AAT is a molecule with a lot of therapeutic importance. For this reason, interest in AAT purification from human plasma or its production in a recombinant version has grown considerably in recent years. This article retraces all technological advances that allowed the manufacturers to move from a few micrograms of partially purified AAT to several grams of highly purified protein. Moreover, the chronic augmentation and maintenance therapy in individuals with emphysema due to congenital AAT deficiency (current applications in the clinical setting) is also presented.

Purification and characterization of alpha 1-proteinase inhibitor from microsomal fraction of normal human liver

A plasma alpha 1-proteinase inhibitor was purified, for the first time, from the microsomal fraction of normal human liver by combined procedures of deoxycholate extraction, (NH4)2-SO4 precipitation, gel filtration and immunoadsorbent column chromatographies. The final yield of the material was approx. 15 mg/300 g liver. The preparation was shown to be homogeneous according to polyacrylamide gel electrophoretic and immunological criteria. The estimated molecular weight of the glycoprotein as determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis was 53 000, a value comparable to that reported for plasma alpha 1-proteinase inhibitor. The liver material was, however, devoid of trypsin-, chymotrypsin- or elastase-inhibitory activity. The loss of activity could be due to deoxycholate treatment during the extraction procedure. SDS-polyacrylamide gel electrophoresis of reduced (beta-mercaptoethanol) and alkylated (iodoacetamide) preparation revealed no change in mobility suggesting the presence of only polypeptide chain. The amino acid and carbohydrate compositions of the microsomal material were in close agreement with values reported in the literatures for the corresponding glycoprotein purified from the plasma. The liver microsomal alpha 1-proteinase inhibitor has a single amino terminal residue, namely, glutamic acid, as determined by the dansyl procedure, and a single carboxyl terminal residue, lysine as shown by the carboxypeptidase digestion method. These terminal amino acids are the same as those found in alpha 1-proteinase inhibitor purified from normal human plasma.