Porcine tissue plasminogen activator. Immunoaffinity purification, structural properties and glycosylation pattern

Tissue plasminogen activator was purified in high yield from pig heart by immunoaffinity chromatography and characterized by analysis of the glycosylation pattern and the N-terminal amino acid sequence. Comparisons with the human enzyme reveals residue exchanges in the A-chain at positions 3 (porcine Arg/human Gln) and 5 (Thr/Ile), and in the B-chain at positions 6 (Tyr/Phe), 10 (Thr/Ala) and 20 (Val/Ala). The glycosylation pattern for the porcine activator was determined by endoglycosidase treatment followed by gel electrophoresis. The A-chain contains a single high-mannose type of N-linked glycan structure and the B-chain contains a complex type of oligosaccharide. A similar but not identical pattern has been observed for the human activator, purified from melanoma cells.