Influence of SK-potentiator and fibrinogen degradation products on the activation of human plasminogen by streptokinase

The activation of plasminogen by T-PA-PAI-1 complex in the absence of fibrin

The activity of tissue plasminogen activator-plasminogen activator inhibitor-1 (t-PA-PAI-1) complex to convert plasminogen to plasmin was examined by using fibrin autography and casein zymography where plasminogen was added or removed for casein layer. Fibrin autography was more sensitive to the activity of t-PA even in the complex with PAI-1, but casein zymography was more sensitive to plasmin. The inhibitory activity of PAI-1 toward t-PA diminished when plasma was clotted, thus in the presence of fibrin. These results indicate that t-PA-PAI-1 complex has a catalytic activity even in the absence of fibrin, but the activity is enhanced in its presence.

The effects of polysaccharides on plasminogen activation by single chain-and two chain-tissue plasminogen activator

We examined the effects of polysaccharides on t-PA mediated plasminogen activation using single-chain tissue plasminogen activator (sct-PA) and two-chain tissue plasminogen activator (tct-PA). Unfractionated heparin, low molecular weight heparin (LMW heparin) and dextran sulfates enhanced the activation rate of plasminogen by sct-PA about three-fold to six-fold. Chondroitin sulfate C did not enhance the activation. The activation of plasminogen by tct-PA was slightly enhanced by unfractionated heparin, but not by other polysaccharides. Conversion of sct-PA to tct-PA was not stimulated by polysaccharides. SDS-PAGE showed no enhancement of the conversion from sct-PA to tct-PA by plasmin in the presence of polysaccharides. However, the enhancement of sct-PA mediated activation of plasminogen by unfractionated heparin, LMW heparin and dextran sulfates in the presence of aprotinin was shown with SDS-PAGE. It was suggested that unfractionated heparin, LMW heparin and dextran sulfates form complex with sct-PA and plasminogen, and stimulate the conversion of sct-PA to tct-PA.

Kinetic analyses of the enhancement of the activities of t-PA induced by the presence of monoclonal antibody (C9-5)

Nine monoclonal antibodies (Mab) against two chain tissue plasminogen activator (t-PA(W] were obtained. The effects of these Mabs on the enzymatic activities of one chain t-PA (t-PA(TD] and two chain t-PA (t-PA(W] were examined by incubating t-PA and Mabs with S-2288, or with plasminogen (plg) and S-2251 in the presence or absence of fibrin. One of Mabs called C9-5 significantly enhanced the activities of t-PA, which were kinetically analyzed. The kinetic analyses of the hydrolysis of S-2288 by t-PA showed increase in kcat from 5.17/sec to 7.75/sec in the presence of 75 micrograms/ml of C9-5 without change in Km. When Glu-plg was activated by t-PA(TD) in the absence of fibrin, Km decreased from 2 microM to 0.17 microM in the presence of C9-5 without change in Vmax. The addition of fibrin resulted in further decrease in Km from 0.133 microM to 0.077 microM. When Lys-plg was activated by t-PA(TD) in the absence of fibrin, Km decreased from 0.408 microM to 0.185 microM in the presence of C9-5, and kcat increased from 0.131 sec-1 to 0.465 sec-1. The presence of fibrin further increased kcat of the activation of Lys-plg. Similar results were obtained when plasminogen was activated by t-PA(W). Mab, C9-5, was shown to bind to B-chain of t-PA by immunoblotting. These results suggest that a dimolecular complex of t-PA and C9-5 has a higher affinity to plasminogen in the presence or absence of fibrin.

Activation of Val442-plasminogen (mini-plasminogen) by urokinase, streptokinase and tissue plasminogen activator

Glu-plasminogen (Glu-plg), Lys-plg and Val442-plg (mini-plg) were activated by urokinase (UK), streptokinase (SK) or tissue plasminogen activator (t-PA). Their activation rates were kinetically analyzed. UK activated Lys-plg with smaller Km and nearly identical Vmax as Glu-plg. Mini-plg was activated by UK with higher Vmax but with the same Km as Glu-plg. On the other hand, t-PA activated Glu-plg, Lys-plg and mini-plg with the same Vmax, but Km was in the order of Glu-plg greater than mini-plg greater than Lys-plg. Fibrin hardly enhanced the UK activation of mini-plg, and fibrinogen, fragment D or E did not enhance the activation of mini-plg by UK. Only D domain, but not E domain, complexed with K5 of mini-plg and SK hydrolysed S-2251 faster than a dimolecular complex of mini-plg and SK, thus a trimolecular mixture of D, SK and mini-plg having a better activator activity than SK-mini-plg complex. In the t-PA activation of mini-plg, fibrin and fibrinogen enhanced the activation, but fragment D or E was ineffective, suggesting that a molecule containing more than one domain was required for the enhanced activation of mini-plg by t-PA.

Clinical study of urokinase-bound fibrocollagenous tubes

Dacron-reinforced fibrocollagenous tubes (FCT) were synthesized from canine mongrels using the mandril-rod technique in order to develop a small diameter (i.e., 4 mm i.d.) vascular graft. They were rendered fibrinolytic by immobilizing urokinase on to the inner surface of the tubes. Urokinase-bound fibrocollagenous tubes (UK-FCT), control FCTs (i.e., no bound enzyme), Perloff grafts (Dr. Perloff, Department of Surgery, University Medical Center, Sidney Australia, has developed a mandril-derived collagenous tube from goats. Samples were implanted for comparative purposes.) and autogeneous saphenous veins, were interposed in the carotid or femoral artery in chronic studies involving 21 canine mongrels. On the basis of Doppler auscultation and palpation, the UK-FCTs were statistically more patent than other candidate prostheses. Fibrin degradation product (FDP) increased in the dogs' systemic circulation with a postoperative peak of 5 days. The host's increase in fibrinolytic activity was shown to be local to the anastamosis. A carotid arterial extracorporeal shunt was designed to evaluate acute patency. Results indicated a rapid thrombosis but no platlet or fibrin adherence to the graft surface was observed, as evidenced by scanning electron microscopy.

The activation of Glu- and Lys-plasminogens by streptokinase: effects of fibrin, fibrinogen and their degradation products

Studies were performed on the activation of a native form of human plasminogen (Glu-plg) or its degraded form (Lys-plg) by streptokinase (SK) in the presence of fibrin, fibrinogen, SK-potentiator, fragment D or E. When Glu-plg (0.1 microM) was activated by 0.5 u/ml of SK in the presence of 100 micrograms of S-2251 and 0.1 microM of fibrin, fibrinogen or their degradation products (potentiating agents), fibrin enhanced the rate of the hydrolysis of S-2251 to the largest extent. Fragments D and E only slightly enhanced it. The order of effectiveness of enhancement was fibrin greater than SK-potentiator greater than fibrinogen greater than D greater than E. When Lys-plg (0.1 microM) was activated by 0.5 u/ml of SK in the presence of potentiating agents, SK-potentiator enhanced the hydrolysis of S-2251 to the largest extent. The enhancement was far less in comparison to the enhancement of the hydrolysis by Glu-plg and SK. The measurement of delta OD405/min at the time of 50% hydrolysis of the substrate was performed in order to compare the effects of concentrations of potentiating agents. The maximum enhancement was obtained at almost an equimolar ratio of plasminogen and fibrin. Fifty percent enhancement was obtained at 0.05 microM for SK-potentiator, 0.072 microM for fibrinogen, 0.21 microM for D and 0.35 microM for E. Fibrin caused the largest extent of enhancement among other potentiating agents. These results may indicate that a trimolecular complex between SK, plasminogen and potentiating agents hydrolyzes S-2251 more effectively than SK-plasminogen complex, thus a trimolecular complex being a better activator than SK-plasminogen complex. Although D and E enhanced only slightly the rate of hydrolysis of S-2251 at equimolar ratio to plasminogen, increase in their concentration resulted in the same extent of enhancement as shown in the presence of fibrinogen or SK-potentiator.

Activation of plasminogen by tissue activator is increased specifically in the presence of certain soluble fibrin(ogen) fragments

Tissue activator-mediated plasminogen activation is potentiated both by fibrin and by some soluble fibrin(ogen) fragments. The potentiating effect of the different fragments decreases in the order fibrin monomer greater than D-dimer greater than Y greater than D EGTA greater than Dcate greater than X. Fibrinogen and the fragments Ecate, E EGTA and E fibrin have almost no effect. The existence of a fibrin polymer is apparently not a prerequisite for this potentiating effect. The plasminogen activation by various urokinase preparations is not potentiated by fibrin and fibrin(ogen) fragments.

Potentiation of the activation of Glu-plasminogen by streptokinase and urokinase in the presence of fibrinogen degradation products

When Glu-plasminogen was activated by streptokinase (SK), the presence of early degradation products of fibrinogen (FgDP) enhanced the rate of activation. When various fragments of FgDP were fractionated, FgDP-Y and E fragments had a potentiating activity while D fragment did not. When Glu-plasminogen was activated by urokinase (UK), the activation rate was enhanced by every fragment of FgDPs, i.e. X, Y, D and E. Although both D and E fragments seem to be able to bind with lysine binding sites of Glu-plasminogen, and to enhance the activation rate by UK, only binding of E fragment with plasminogen can result in enhancement of the activation of Glu-plasminogen by SK.