Comparison of the effects of fibrinogen and fibrin products and isolated peptide chains on the fibrin-mediated stimulation of plasminogen activation by tissue-type plasminogen activator, and on the fibrin-dependent enhancement of the amidolytic activity of one-chain tissue-type plasminogen activator.
Intact fibrin monomer, the early fibrin degradation product (X-fragment), late fibrinogen degradation products (fragments D and E), fibrinogen cyanogen bromide fragment FCB-2, and isolated peptide chains of fibrinogen and fibrin were investigated for their ability to replace fibrin in the stimulation of one-chain tissue-type plasminogen activator. They were also investigated for their ability to stimulate plasminogen activation by one-chain tissue-type plasminogen activator, which occurs via ternary complex formation. The stimulatory effect of the different fibrin/ogen products decreased in the order: fibrin X-fragment greater than fibrin monomer greater than CNBr-fragment FCB-2 greater than fibrin alpha-chain. Fibrin beta/gamma-chains and fibrinogen peptide chains were found to be weak stimulators. Fibrinogen fragments D and E have almost no effect. The amidolytic activity of one-chain tissue-type plasminogen activator was stimulated by intact fibrin monomer and somewhat more strongly by fibrin X-fragment. This stimulation by fibrin monomer, which occurred via an increase in the kcat value, was competitively inhibited by isolated fibrin alpha-chain (Ki = 0.12 mumol/l). The results show that the fibrin-mediated stimulation of plasminogen activation occurs when both one-chain tissue-type plasminogen activator and plasminogen are bound to fibrin, and that this process is essentially independent of the conformation of the fibrin molecule. In comparison, the fibrin-dependent stimulation of the amidolytic activity of one-chain tissue-type plasminogen activator is a more complex process, which depends on the correct conformation of the fibrin molecule.
Fischer
B
B
FZB/Biotechnology GmbH, Berlin.
D000595:Amino Acid Sequence; D003488:Cyanogen Bromide; D005337:Fibrin / Q000494:pharmacology*; D005338:Fibrin Fibrinogen Degradation Products / Q000494:pharmacology; D005340:Fibrinogen / Q000494:pharmacology*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D010958:Plasminogen / Q000378:metabolism*; D011487:Protein Conformation; D013917:Thrombin / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000378:metabolism*
D005338:Fibrin Fibrinogen Degradation Products; C015214:fibrinogen D fragment; C018543:fibrinogen fragment E; D005337:Fibrin; D005340:Fibrinogen; D010958:Plasminogen; D013917:Thrombin; D010959:Tissue Plasminogen Activator; D003488:Cyanogen Bromide