Plasminogen activation by tissue plasminogen activator in the presence of stimulating CNBr fragment FCB-2 of fibrinogen is a two-phase reaction. Kinetic analysis of the initial phase of slow plasmin formation.
Plasminogen activation by tissue-type plasminogen activator (t-PA) is stimulated by fibrin. In a purified system maximal fibrin-enhanced plasmin formation occurs with a delay after an initial phase of slow plasmin formation (lag phase). In the present study purified stimulating CNBr-fragment FCB-2 of fibrinogen was used, and kinetics of plasminogen activation by t-PA were analyzed with respect to the lag phase. At constant FCB-2 concentration the duration of the lag phase decreased with increasing concentrations of t-PA and plasminogen. During this period the rate of plasmin formation/min increased linearly with time with a slope dependent on the initial concentrations of FCB-2, plasminogen, and t-PA. Plasmin pretreatment of FCB-2 resulted in a dose- and time-dependent shortening of the lag phase, and at plasmin concentrations greater than or equal to 1 nM and preincubation times greater than or equal to 3 min maximal plasmin formation occurred without a lag phase. Kinetics during the phase of maximal and constant plasmin formation were not influenced by plasmin pretreatment of FCB-2. We therefore conclude that maximal t-PA-dependent plasmin formation in a system stimulated by purified FCB-2 requires plasmin modification of FCB-2.
Beckmann
R
R
Department of Medical Physiology, University of Vienna, Austria.
Geiger
M
M
Binder
B R
BR
D003488:Cyanogen Bromide; D004789:Enzyme Activation; D005340:Fibrinogen / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010446:Peptide Fragments / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
D010446:Peptide Fragments; D005340:Fibrinogen; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D003488:Cyanogen Bromide