Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Beside the direct inhibition of thrombin and its regulatory functions, many of the newer antithrombin agents produce several additional effects, unrelated to their anticoagulant actions. Synthetic peptide inhibitors are capable of producing fibrinolytic compromise by virtue of their actions on fibrinolytic enzymes such as t-PA, plasmin, urokinase and protein Ca. In addition, the low molecular weight arginine-containing peptides are also known to produce hemodynamic and hemostatic deficits. The designs of the ongoing clinical trials are largely empirical because of the non-availability of valid pharmacologic and toxicologic data on thrombin inhibitors. In contrast to heparin, none of the thrombin inhibitors produce endogenous release of tissue factor pathway inhibitor (TFPI) in the experimental and clinical settings. These observations suggest that beside the direct inhibition of thrombin, these agents also produce multiple additional effects that can significantly contribute to their pharmacologic and toxicologic profile.
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PMID:Comparative pharmacology of site directed antithrombin agents. Implication in drug development. 857 9

Since thromboembolic complications in transplanted patients are generally attributed to combined abnormalities in platelets and coagulo-lytic system, some hemostatic parameters tPA (tissue plasmogin activator):Ag and activity, its inhibitor-PAIAg and activity, tPA/PAI, thrombin-antithrombin (TAT) and plasmin-antiplasmin complexes (PAP), urokinase-uPA, euglobulin clot lysis time-ECLT, fibrinogen, plasminogen, protein C activity, D-dimer, prothrombin fragments1+2 (F1+2), fibrin monomers, fibronectin, lipoprotein-a, and von Willebrand factor(vWF), were evaluated using commercially available kits. The studies were performed on kidney transplant recipients treated with CsA, azathioprine and prednisone (n=21), and healthy volunteers (n=21). ECLT was significantly prolonged in kidney transplant recipients together with a rise in F1+2,lipoprotein-a, fibrinogen, fibronectin, and vWF when compared with controls. The TPA level was lower, whereas the PAI level was higher in kidney transplant recipients when compared with controls. In conclusion, CsA-treated kidney transplant recipients show evidence of pronounced impairment in fibrinolysis and endothelial damage in comparison with healthy volunteers.
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PMID:The coagulo-lytic system and endothelial function in cyclosporine-treated kidney allograft recipients. 882 84

Barley serpin BSZx is a potent inhibitor of trypsin and chymotrypsin at overlapping reactive sites (Dahl, S.W., Rasmussen, S.K. and Hejgaard, J. (1996) J. Biol. Chem., in press). We have now investigated the interactions of BSZx with a range of serine proteinases from human plasma, pancreas and leukocytes, a fungal trypsin and three subtilisins. Thrombin, plasma kallikrein, factor VIIa/tissue factor and factor Xa were inhibited by BSZx at heparin independent association rates (k(ass)) of 4.5 X 10(3)-1.3 x 10(5) M(-1) s(-1) at 22 degrees C. Only factor Xa turned a significant fraction of BSZx over as substrate. Complexes of these proteinase with BSZx resisted boiling in SDS, and amino acid sequencing showed that cleavage in the reactive center loop only occurred after P1 Arg. Activated protein C and leukocyte elastase were slowly inhibited by BSZx (k(ass)=1-2 x 10(2) M(-1) s(-1)) whereas factor XIIa, urokinase and tissue type plasminogen activator, plasmin and pancreas kallikrein and elastase were not or only weakly affected. The inhibition pattern with mammalian proteinases reveal a specificity of BSZx similar to that of antithrombin III. Trypsin from Fusarium was not inhibited while interaction with subtilisin Carlsberg and Novo was rapid but most BSZx was cleaved as a substrate. Identification of a monoclonal antibody specific for native BSZx indicate that complex formation and loop cleavage result in similar conformational changes.
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PMID:Inhibition of coagulation factors by recombinant barley serpin BSZx. 884 56

A pathogenetic role for fibrin deposition and platelet activation in the kidney is thought to play a role in the pathogenesis of acute renal failure (ARF). Thus, some fibrinolytic parameters and platelet function have been studied in 17 patients with ARF and compared to healthy volunteers and subjects with chronic renal failure (CRF). Since serotonin may participate in pathological processes resulting from platelet/vessel wall interactions, its level in the whole blood and plasma was also assayed. In ARF and CRF platelet aggregatory responses in both whole blood and in platelet rich plasma upon stimulation with various agonists (collagen, arachidonic acid, ADP, ristocetin) were lower than those obtained in healthy volunteers. Increased levels of lipoprotein (a), von Willebrand factor (vWF) and fibronectin were found in ARF relative to controls. Protein C activity was significantly lower in patients with ARF. Euglobulin clot lysis time was prolonged in ARF and CRF, reflecting a decreased overall fibrinolytic activity. Activity of tissue plasminogen activator (tPA) inhibitor (PAI) and PAI:Ag were higher in ARF, whereas tPA:Ag, urokinase, tPA/PAI complexes, thrombin-antithrombin complexes (TAT), plasmin-antiplasmin (PAP) complexes, fibrinogen, and F1+2 did not differ between ARF and controls. In CRF elevated levels of TAT, PAP, fibrinogen and prothrombin fragments F1+2 were found, whereas concentration of fibronectin was lowered when compared to controls. In both groups of renal failure patients increased levels of fibrin monomers and d-dimer were found relative to healthy volunteers. Whole blood serotonin was significantly lower, whereas plasma serotonin was significantly higher in patients with ARF and CRF relative to controls. Serotonin uptake and its release from platelets were markedly diminished in patients with ARF and CRF. Chronic renal failure exhibit a slightly different pattern of coagulopathies that acute renal failure.
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PMID:Hemostasis, platelet function and serotonin in acute and chronic renal failure. 887 44

The kinetic parameters were determined for the hydrolysis of a peptide based on the activation site of the thrombin receptor (residues 38-60) by thrombin and 12 other proteases. The kcat and Km values for the cleavage of this peptide (TR39-40) by thrombin were 107 s-1 and 1.3 microM; the kcat/Km of TR39-40 is among the highest observed for thrombin. A model is presented that reconciles the parameters for cleavage of the peptide with the concentration dependence of cellular responses to thrombin. Cleavage of TR39-40 was not specific for thrombin. The pancreatic proteases trypsin and chymotrypsin hydrolysed TR39-40 efficiently (kcat/Km > 10(6) M-1.s-1). Whereas trypsin cleaved TR39-40 at the thrombin activation site (Arg41-Ser42), chymotrypsin hydrolysed the peptide after Phe43. This chymotryptic cleavage would result in inactivation of the receptor. The efficient cleavage of TR39-40 by chymotrypsin (kcat/Km approximately 10(6) M-1.s-1) was predominantly due to a low Km value (2.8 microM). The proteases factor Xa, plasmin, plasma kallikrein, activated protein C and granzyme A also hydrolysed TR39-40 at the Arg41-Ser43 bond, but exhibited kcat/Km values that were at least 10(3)-fold lower than that observed with thrombin. Both tissue and urokinase plasminogen activators as well as granzyme B and neutrophil elastase were unable to cleave TR39-60 at appreciable rates. However, neutrophil cathepsin G hydrolysed the receptor peptide after Phe55. Like the chymotryptic cleavage, this cleavage would lead to inactivation of the receptor, but the cathepsin G reaction was markedly less efficient; the kcat/K(m) value was almost four orders of magnitude lower than that for thrombin. In addition to the above cleavage sites, a secondary site for thrombin and other arginine-specific proteases was identified at Arg46, but the cleavage at this site only occurred at very low rates and is unlikely to be significant in vivo.
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PMID:Cleavage of the thrombin receptor: identification of potential activators and inactivators. 894 6

Renal venous thrombosis (RVT) is a serious complication of neonates. In most cases the underlying cause of RVT remains unclear. Here we report a neonate with bilateral RVT and adrenal haemorrhage associated with a heterozygous mutation of the gene encoding for clotting factor V, resulting in resistance to activated protein C. Vigorous thrombolytic therapy with urokinase followed by recombinant tissue plasminogen activator dissolved the thrombus in the inferior vena cava and restored perfusion of both kidneys. However, a haemorrhagic rupture of the right kidney occurred, requiring emergency nephrectomy. Despite reperfusion of the left kidney and resumption of urine output, the patient remained dialysis dependent. Due to persistent adrenal insufficiency, long-term substitution of hydrocortisone was necessary. The patient was prophylactically treated with coumarin during the first 6 months of life and is now waiting for renal transplant at the age of 1 year.
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PMID:Bilateral renal venous thrombosis in a neonate associated with resistance to activated protein C. 897 93

A case of significant proteinuria occurred as a result of bilateral renal vein thrombosis secondary to dehydration, which resolved after treatment with urokinase. The patient developed nausea and vomiting from viral gastroenteritis with subsequent volume contraction. He later noted the onset of aching lower abdominal and flank pain. On admission, he was noted to have a serum creatinine of 1.7 mg/dL, and 4+ proteinuria on urinalysis. A 24-hour urine collection showed 2.34 g protein. A renal venogram showed bilateral renal vein thrombosis (RVT) without involvement of the inferior vena cava. Therapy was initiated with heparin at 1,000 U/hr, followed by intravenous (IV) urokinase, 4,400 U/kg bolus, followed by 4,400 U/kg/hr with continuous infusion for 12 hours. A repeat renal venogram done at this time showed partial resolution of thrombosis bilaterally. A second 12-hour infusion of urokinase at 5,000 U/kg/hr was performed; at this time, the patient reported resolution of his flank and abdominal pain. A repeat 24-hour urine collection showed 60 mg protein with a normal creatinine clearance. Levels of antithrombin III, protein C, and protein S were all normal. A renal biopsy was performed and showed normal histology on light, immunofluorescent, and electron microscopic evaluation. The patient has done well on no therapy and has had no recurrence of thrombosis or proteinuria after 2.5 years. This is a US government work. There are no restrictions on its use.
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PMID:Resolution of proteinuria secondary to bilateral renal vein thrombosis after treatment with systemic thrombolytic therapy. 910 53

A comprehensive study on platelet aggregation, hemostasis, fibrinolysis and serum lipids in relation to peripheral serotonergic system has been performed on 41 nephrotic patients. Enhanced platelet aggregatory responses in both whole blood and in platelet rich plasma (PRP) were found upon stimulation with different agonists when compared to healthy volunteers. Increased levels of fibrinogen, fibrin monomers, and protein C activity were observed in nephrotic patients. Euglobulin clot lysis time was significantly prolonged in nephrotic patients. Activity of tissue plasminogen activator (tPA) inhibitor was higher in nephrotic syndrome, whereas tPA activity was significantly lower in these patients when compared to controls. Urokinase concentration, lipoprotein (a), cholesterol, LDL and VLDL levels were significantly higher in nephrotic patients over controls. Whole blood serotonin was significantly lower, whereas plasma serotonin was significantly higher in nephrotic patients relative to controls. Serotonin uptake and its release from platelets were markedly diminished in patients with nephrotic syndrome. Disequilibrium in the coagulolytic system, platelet hyperactivity, hyperfibrinogenemia, disturbances in peripheral serotonergic system together with lipid abnormalities may contribute to the progression and development of atherosclerosis and an enhanced risk of thromboembolic complications in nephrotic syndrome.
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PMID:Comprehensive study on platelet function, hemostasis, fibrinolysis, peripheral serotonergic system and serum lipids in nephrotic syndrome. 911 50

Suppression of the fibrinolytic activity plays an important role in the prevention of hemorrhage during pregnancy and labor. A hypofibrinolytic and hypercoagulable state may be established in the placenta during pregnancy. However, little infraction is present in the normal placenta. This evidence shows that placenta maintains the fibrinolytic activity in spite of hypercoagulable state. As there is a high amount of APC in the placenta, APC is thought to be involved in fibrinolysis of placenta. Thus, we studied the role of APC on fibrinolysis in placenta. (1) uPA activity of cell membrane reappears after incubation with uPA/PAI-1 complex and a large amount of APC by flow cytometry, (2) APC was made PAI-1/APC complex after incubation of uPA/PAI-1 complex with APC. Our results suggest that APC is the important substance for fibrinolysis in the placenta by decreasing of PAI activity.
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PMID:Relationship of urokinase type plasminogen activator, plasminogen activator inhibitor type 1 and activated protein C in fibrinolysis of human placenta. 911 54

Members of the serpin (serine protease inhibitor) family share a similar backbone structure but expose a variable reactive-site loop, which binds to the catalytic groove of the target protease. Specificity originates in part from the sequence of this loop and also from secondary binding sites that contribute to the inhibitor function. To clarify the intrinsic contribution of the reactive-site loop, alpha1-antichymotrypsin has been utilized as a scaffold to construct chimeras carrying the loop of antithrombin III, protease nexin 1, or alpha1-antitrypsin. Reactive-site loops not only vary in sequence but also in length; therefore, the length of the reactive-site loop was also varied in the chimeras. The efficacy of the specificity transfer was evaluated by measuring the stoichiometry of the reaction, the ability to form an SDS-stable complex, and the association rate constant with a number of potential targets (chymotrypsin, neutrophil elastase, trypsin, thrombin, factor Xa, activated protein C, and urokinase). Overall, substitution of a reactive-site loop was not sufficient to transfer the specificity of a given serpin to alpha1-antichymotrypsin. Specificity of the chimera partly matched that of the loop donor and partly that of the acceptor, whereas the behavior as an inhibitor or a substrate depended upon the targeted protease. Results suggest that, aside from the contributions of the loop sequence and the framework-specific secondary binding sites, an intramolecular control may be essential for productive interaction.
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PMID:Intrinsic specificity of the reactive site loop of alpha1-antitrypsin, alpha1-antichymotrypsin, antithrombin III, and protease nexin I. 919 29


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