N‐terminal amino acid sequences of precursor and mature forms of α‐1‐antitrypsin

Abstract

α-1-Antitrypsin is found in hepatocytes as a high-mannose glycoprotein (M _r 49000), extracellularly as a complex-type glycoprotein (M _r 54000). Deglycosylation of both forms with peptide: N-glycosidase led to proteins of identical app. M _r (41000). The sequence of 26 N-terminal amino acids of rat α₁-antitrypsin was determined. A high content of polar amino acids was found. The partially characterized presequence of in vitro synthesized α₁-antitrypsin showed a cluster of hydrophobic amino acids. A pre-peptide of 24 amino acids is proposed. There is no evidence for the existence of a propeptide.