Plasminogen activator

The concentration of t-PA in human blood is 2—5 ng/mL, ie, 2—5 ppb. Plasminogen activation is accelerated in the presence of a clot, but the rate is slow. The dissolution of a clot requites a week or more during normal repair of vascular damage (17). Prevention of irreversible tissue damage during a heart attack requires that a clot, formed by mpture of an atherosclerotic plaque, be dissolved in a matter of hours. This rapid thrombolysis (dissolution of the clot) must be achieved without significant tibrinogenolysis elsewhere in the patient. 

Fig. 2. Outline of possible steps in the recovery and purification sequence for recombinant tissue plasminogen activator derived from recombinant CHO...

Fig. 3. Overview of puriftcation sequence for the nonrecombinant tissue plasminogen activator (t-PA) which also contains urokinase plasminogen activator (u-PA). Serum-free culture conditional media is from normal human ceU line. The temperature for aU. steps, except for size-exclusion chromatography...

S. E. Builder, R. van Reis, N. Paoni, and J. Ogez, "Process Development and Regulatory Approval of Tissue-Type Plasminogen Activator," in... 

Protein G. This vitamin K-dependent glycoproteia serine protease zymogen is produced ia the Hver. It is an anticoagulant with species specificity (19—21). Proteia C is activated to Proteia by thrombomodulin, a proteia that resides on the surface of endothefial cells, plus thrombin ia the presence of calcium. In its active form, Proteia selectively iaactivates, by proteolytic degradation. Factors V, Va, VIII, and Villa. In this reaction the efficiency of Proteia is enhanced by complex formation with free Proteia S. la additioa, Proteia activates tissue plasminogen activator, which... 

Although the precise mechanism of plasminogen activation is unknown, three principal theories have developed based on studies of the in vitro activation of native human plasminogen. Activation of native Glu-plasminogen in the absence of any plasmin inhibitor yields Lys —plasmin plus the so-called pre-activation peptides (PAP) formed by cleavage at LySg2 S E3 Activation takes place by a two-step mechanism in... 

The high affinity LBS is involved in the interaction of plasminogen with fibrin, a2-antiplasmin, and a plasmin inhibitor called histidine-rich glycoprotein. It has been observed that plasminogen activation takes place on the surface of fibrin and that a2-antiplasmin competitively inhibits the plasminogen—fibrin interaction at the high affinity LBS. 

Fig. 4. Fibrinolytic system where SCUPA is single-chain urokinase plasminogen activator rTPA is recombinant tissue plasminogen activator APSAC is acylated plasminogen streptokinase activator complex SK is streptokinase and UK is urokinase.

As of early 1992, the market for ceU culture-derived products approached 1 billion per year. The market is expected to grow substantially throughout the 1990s. CeU culture products include erythropoietin, 1991 sales of approximately 400 million, for the treatment of anemia associated with kidney dialysis, and tissue plasminogen activator, 1991 sales approximately 200 million, for treating heart attack victims with blocked arteries (see Cardiovascularagents). 

Tissue Plasminogen Aetivator (tPA). While streptokinase and urokinase can effectively induce clot dissolution in the majority of patients if given early, they lack clot specificity. Treatment with these enzymes results in a systemic lytic state attributable to their degradative action on circulating fibrinogen. Tissue plasminogen activator (tPA) was developed to achieve rapid and specific thrombolysis. 

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