Interaction of mature, unglycosylated and cell‐free synthesized rat α1‐proteinase inhibitor with elastase

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Abstract
Purified rat α1‐proteinase inhibitor (Mr 54 000) and porcine pancreatic elastase (Mr 26 000) formed a complex (Mr 82 000) resistant to heat treatment under denaturing and reducing conditions. A similar α1‐proteinase‐inhibitor‐elastase complex was detected by immunoprecipitation of α1‐proteinase inhibitor from the medium of [35S]methionine‐labeled hepatocyte primary cultures after incubation with elastase. Treatment of hepatocytes with tunicamycin led to the secretion of an unglycosylated α1‐proteinase inhibitor (Mr 41 000) which also formed a complex with elastase (Mr 66 000). Complex formation (Mr 68 000) could also be observed between cell‐free synthesized pre‐α1‐proteinase inhibitor (Mr 43 000) and elastase (Mr 26 000).The results suggest that neither glycosylation nor removal of the signal peptide are required for the formation of a biologically active conformation of α1‐proteinase inhibitor.