» Articles » PMID: 1531588

Generation of Forms of Fragment E with Differing Thrombin-binding Properties During Digestion of Fibrinogen by Plasmin

Overview
Journal Biochem J
Specialty Biochemistry
Date 1992 Feb 1
PMID 1531588
Authors
Affiliations
Soon will be listed here.
Abstract

Two principal forms of fragment E are generated upon digestion of fibrinogen by plasmin, according to the concentration of enzyme used. At a high concentration of plasmin (above 10 micrograms/ml), a form lacking fibrinopeptide A (FpA) at the N-terminus of the A alpha-chain was generated. This form of fragment E caused a dose-dependent increase in thrombin clotting times but had no measurable inhibitory activity towards thrombin cleavage of D-phenylalanyl-L-pipecolyl-L-arginine p-nitroanilide. At a low concentration of plasmin (less than 1 microgram/ml), fragment E containing 35-40% of the original amount of FpA was present in the terminal digest. The FpA-containing form of fragment E inhibited thrombin cleavage of fibrinogen, inhibited amidolytic activity and bound to the enzyme with an affinity 3-fold tighter than fibrinogen itself (Kd 4.1 +/- 0.3 microM as opposed to 12.7 +/- 1.8 microM). During digestion of fibrinogen at low plasmin concentration, up to 65% of the FpA was cleaved just subsequent to the progressive release of B beta-(1-42)-peptide, and the Arg-16-Gly-17 bond of the A alpha-chain became relatively stable towards plasmin action when present in fragment E (and possibly fragment Y). It is proposed that both forms of fragment E can inhibit clotting by binding to the fibrin(ogen)-recognition site (anion-binding exosite) of thrombin. The FpA-containing form of fragment E can also inhibit binding that occurs distal to the P1 site and thereby interfere with amidolysis of the peptide substrate. Our finding of a lability of the Arg-16-Gly-17 bond in the early phase of digestion may provide an alternative explanation of the increased FpA concentrations observed during thrombolytic therapy.

References
1.
Olexa S, Budzynski A, Doolittle R, Cottrell B, Greene T . Structure of fragment E species from human cross-linked fibrin. Biochemistry. 1981; 20(21):6139-45. DOI: 10.1021/bi00524a035. View

2.
Doolittle R . Fibrinogen and fibrin. Annu Rev Biochem. 1984; 53:195-229. DOI: 10.1146/annurev.bi.53.070184.001211. View

3.
Lundblad R, Nesheim M, Straight D, Sailor S, Bowie J, Jenzano J . Bovine alpha- and beta-thrombin. Reduced fibrinogen-clotting activity of beta-thrombin is not a consequence of reduced affinity for fibrinogen. J Biol Chem. 1984; 259(11):6991-5. View

4.
Scully M, Kakkar V . Structural features of fibrinogen associated with binding to chelated zinc. Biochim Biophys Acta. 1982; 700(1):130-5. DOI: 10.1016/0167-4838(82)90301-6. View

5.
Marsh Jr H, Meinwald Y, Lee S, Scheraga H . Mechanism of action of thrombin on fibrinogen. Direct evidence for the involvement of phenylalanine at position P9. Biochemistry. 1982; 21(24):6167-71. DOI: 10.1021/bi00267a022. View