Isolation and characterization of two minor fractions of α₁,-antitrypsin by high-performance liquid chromatographic chromatofocusing

α₁-Antitrypsin is a glycoprotein that separates into five electrophoretic fractions, viz. M₂, M₄, M₆, M₇ and M₈. Con A-Sepharose separates the protein into three fractions according to the branching degree of the three oligosaccharide chains. The Con A affinity is identical for M₄ and M₇ and for M₆ and M₈. Within each pair the proteins were isolated by rapid chromatofocusing. The M₇ and M₈ have the same carbohydrate structure as the major M₄ and M₆ respectively, but have lost the first five N-terminal amino acids (Glu-Asp-Pro-Glu-Gly) as compared to the majority of the protein.