title: Comparison of structures of various human fibrinogens and a derivative thereof by a study of the kinetics of release of fibrinopeptides.
abstract: The kinetics of the thrombin-induced release of fibrinopeptides from several variants of human fibrinogen, and from the plasmin digestion fragment E thereof, have been studied by using an HPLC technique to separate the reaction products. The data were analyzed in terms of a Michaelis-Menten mechanism in which the A alpha and B beta chains compete for thrombin. Phosphorylation of Ser-3 of the A alpha chain appears to increase the rate of release of the corresponding phosphorylated peptide A from fibrinogen, due to enhanced binding of thrombin (lower value of the Michaelis-Menten constant KM). However, phosphorylation does not affect the rate of release of the unphosphorylated A or B peptides. Increase in the length of the gamma chain (at the C-terminus) does not affect the rate of release of any of the fibrinopeptides. The rate of release of the A peptide from fragment E (which is devoid of the B peptide) is similar to that for the complete fibrinogen molecule. These results are in agreement with an earlier conclusion [Martinelli, R. A., & Scheraga, H. A. (1980) Biochemistry 19, 2343] that the A alpha and B beta chains behave independently in their competition for thrombin; i.e., the hydrolyzable Arg-Gly bonds of the A alpha and B beta chains are both accessible to thrombin.
mesh_terms: D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D005344:Fibrinopeptide A / Q000378:metabolism; D005345:Fibrinopeptide B / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008433:Mathematics; D010766:Phosphorylation
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; D046911:Macromolecular Substances; C018543:fibrinogen fragment E; D005344:Fibrinopeptide A; D005345:Fibrinopeptide B; D005340:Fibrinogen; D005341:Fibrinolysin