Plasminogen Activators: Pharmacology and Therapy

Holden, Robert W.

doi:10.1148/radiology.174.3.174-3-993

Cited by 57 publications

(19 citation statements)

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“…Some of these proteases are fibrinolytic enzymes capable of digesting fibrin (Fujita et al 1993;Jeong et al 2004;Leonardi et al 2002;Sumi et al 1995;Wong and Mine 2004). The fibrinolytic agents available today for clinical use are mostly plasminogen activators (Holden 1990), such as tissue-type plasminogen activator, urokinase-type plasminogen activator and the bacterial plasminogen activator, streptokinase. In spite of their widespread use, these agents display low specificity to fibrin and cause undesired side effects.…”

Section: Introductionmentioning

confidence: 99%

Screening and characterization of a novel fibrinolytic metalloprotease from a metagenomic library

et al. 2007

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A metagenomic library was constructed using total genomic DNA extracted from the mud in the west coast of Korea and was used together with a fosmid vector, pCC1FOS in order to uncover novel gene sources. One clone from approximately 30,000 recombinant Escherichia coli clones was identified that showed proteolytic activity. The gene for the proteolytic enzyme was subcloned into pUC19 and sequenced, and a database search for homologies revealed it to be a zinc-dependent metalloprotease. The cloned gene included the intact coding gene for a novel metalloproteinase and its own promoter. It comprised an open reading frame of 1,080 base pairs, which encodes a protein of 39,490 Da consisting of 359 amino acid residues. A His-Glu-X-X-His sequence, which is a conserved sequence in the active site of zinc-dependent metalloproteases, was found in the deduced amino acid sequence of the gene, suggesting that the enzyme is a zinc-dependent metalloprotease. The purified enzyme showed optimal activity at 50 degrees C for 1 h and pH 7.0. The enzyme activity was inhibited by metal-chelating reagents, such as EDTA, EGTA and 1,10-phenanthroline. The enzyme hydrolyzed azocasein as well as fibrin. Thus, the enzyme could be useful as a therapeutic agent to treat thrombosis.

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Section: Introductionmentioning

confidence: 99%

Screening and characterization of a novel fibrinolytic metalloprotease from a metagenomic library

et al. 2007

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“…Although the two agents produce similar patency rates, TNK-t-PA is easier to administer because it has a half-life 8.5-fold longer than that of t-PA (21). Consequently, TNK-t-PA can be given as a single intravenous bolus, whereas t-PA must be given by bolus followed by an infusion (22)(23)(24)(25). The longer half-life of TNK-t-PA, relative to t-PA, is the result of two mutations introduced into the first kringle of t-PA: removal of the high mannose carbo-hydrate at position 117 by substitution of asparagine with glutamine (N117Q, abbreviated N) 2 and creation of a new glycosylation site by replacement of the threonine residue at position 103 with an asparagine (T103N, abbreviated T) (26).…”

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confidence: 99%

Identification of the Mechanism Responsible for the Increased Fibrin Specificity of TNK-Tissue Plasminogen Activator Relative to Tissue Plasminogen Activator

Stewart¹,

Fredenburgh²,

Leslie³

et al. 2000

Journal of Biological Chemistry

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TNK-tissue plasminogen activator (TNK-t-PA), a bioengineered variant of tissue-type plasminogen activator (t-PA), has a longer half-life than t-PA because the glycosylation site at amino acid 117 (N117Q, abbreviated N) has been shifted to amino acid 103 (T103N, abbreviated T) and is resistant to inactivation by plasminogen activator inhibitor 1 because of a tetra-alanine substitution in the protease domain (K296A/H297A/R298A/R299A, abbreviated K). TNK-t-PA is more fibrin-specific than t-PA for reasons that are poorly understood. Previously, we demonstrated that the fibrin specificity of t-PA is compromised because t-PA binds to (DD)E, the major degradation product of cross-linked fibrin, with an affinity similar to that for fibrin. To investigate the enhanced fibrin specificity of TNK-t-PA, we compared the kinetics of plasminogen activation for t-PA, TNK-, T-, K-, TK-, and NK-t-PA in the presence of fibrin, (DD)E or fibrinogen. Although the activators have similar catalytic efficiencies in the presence of fibrin, the catalytic efficiency of TNK-t-PA is 15-fold lower than that for t-PA in the presence of (DD)E or fibrinogen. The T and K mutations combine to produce this reduction via distinct mechanisms because T-containing variants have a higher K M , whereas K-containing variants have a lower k cat than t-PA. These results are supported by data indicating that T-containing variants bind (DD)E and fibrinogen with lower affinities than t-PA, whereas the K and N mutations have no effect on binding. Reduced efficiency of plasminogen activation in the presence of (DD)E and fibrinogen but equivalent efficiency in the presence of fibrin explain why TNK-t-PA is more fibrin-specific than t-PA. Tissue-type plasminogen activator (t-PA)1 is a trypsin-like serine protease that initiates fibrinolysis by converting plasminogen (Pg) to plasmin (1). Plasmin then solubilizes fibrin, yielding fibrin degradation products. Through a positive feedback mechanism, fibrin enhances its own degradation by stimulating t-PA-mediated Pg activation (2). To enhance this reaction, fibrin binds t-PA and Pg, thereby increasing the catalytic efficiency of t-PA-mediated Pg activation 1000-fold over that in the absence of fibrin (2-6). In contrast to the potent stimulatory effect of fibrin, fibrinogen (Fg) produces only modest enhancement in the catalytic efficiency of Pg activation by t-PA (2, 7, 8). Because it preferentially activates Pg in the presence of fibrin rather than Fg, t-PA is designated a fibrin-specific plasminogen activator. Despite its apparent fibrin specificity, t-PA causes systemic fibrinogenolysis and ␣ 2 -antiplasmin consumption when given to patients (9, 10). Recently, we demonstrated that the fibrin specificity of t-PA is compromised because (DD)E, the major degradation product of cross-linked fibrin (11), stimulates Pg activation by t-PA to a similar extent as fibrin (11)(12)(13). This occurs because, like fibrin, (DD)E also binds t-PA and Pg with high affinity, thereby enhancing their interaction (14). As a potent stimulato...

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“…Whereas tPA promotes plasmin-mediated fibrinolysis, dissolving clot, heparin is an anticoagulant acting on the intrinsic pathway, inhibiting coagulation and preventing thrombus progression without leading to its dissolution. The biological half-life of tPA and intravenous heparin is approximately 8 and 60 minutes, respectively (34,35). Whereas tPA is the active medication used to treat PE, heparin is also delivered at a low dose to prevent clot formation in and around access sheaths and catheters.…”

Section: Contraindications To Thrombolysismentioning

confidence: 99%

Catheter-directed interventions for pulmonary embolism

Zarghouni

Charles

Maldonado

et al. 2016

Cardiovasc. Diagn. Ther.

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Pulmonary embolism (PE), a potentially life-threatening entity, can be treated medically, surgically, and percutaneously. In patients with right ventricular dysfunction (RVD), anticoagulation alone may be insufficient to restore cardiac function. Because of the morbidity and mortality associated with surgical embolectomy, clinical interest in catheter-directed interventions (CDI) has resurged. We describe specific catheter-directed techniques and the evidence supporting percutaneous treatments.

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Plasminogen Activators: Pharmacology and Therapy

Cited by 57 publications

References 0 publications

Screening and characterization of a novel fibrinolytic metalloprotease from a metagenomic library

Screening and characterization of a novel fibrinolytic metalloprotease from a metagenomic library

Identification of the Mechanism Responsible for the Increased Fibrin Specificity of TNK-Tissue Plasminogen Activator Relative to Tissue Plasminogen Activator

Catheter-directed interventions for pulmonary embolism

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