title: The influence of fibrin(ogen) fragments on the kinetic parameters of the tissue-type plasminogen-activator-mediated activation of different forms of plasminogen.
abstract: In the present work we have determined Km,app and kcat,app values for tissue-type plasminogen-activator-catalyzed activation of Glu-plasminogen, Lys-plasminogen and mini-plasminogen in the absence and in the presence of fibrinogen-derived fragments. These were CNBr fragment 2, the A alpha chain remnant of CNBr fragment 2 (A alpha 148-207) and plasmin-generated fragment D-EGTA. The time course of plasmin formation from the various types of plasminogen (plg) was measured spectrophotometrically in a coupled assay system where D-valyl-L-leucyl-L-lysine p-nitroanilide served as a plasmin substrate. The kinetic constants are summarized as follows. (Values in parentheses are concentrations at which the minimum Km,app and maximum kcat,app value is reached.) (Table: see text). In conclusion our results show that CNBr fragment 2, A alpha 148-207 and to some extent D-EGTA mimic the accelerating effect of fibrin. The first two of these fragments did not accelerate activation of mini-plasminogen, lacking the kringle structures I-IV. This suggests that the stimulating effects of these two fragments were dependent on the presence of kringles I-IV of the plasminogen molecule.
mesh_terms: D002384:Catalysis; D003488:Cyanogen Bromide; D004789:Enzyme Activation / Q000187:drug effects; D005338:Fibrin Fibrinogen Degradation Products / Q000494:pharmacology; D005340:Fibrinogen / Q000494:pharmacology*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D010958:Plasminogen / Q000494:pharmacology*; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; D005340:Fibrinogen; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D003488:Cyanogen Bromide