Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 77-kDa complex of thrombin and a protein secreted by activated platelets had little if any thrombin amidolytic activity, indicating that the secreted protein is an inhibitor. The molecular weight of the inhibitor before reaction with thrombin was approximately 50,000. The apparent second-order rate constant for complex formation was estimated to be 1.3 x 10(6) M-1 s-1 (mean of four measurements); it was not affected by heparin or heparinase. These properties distinguish this inhibitor from other protease inhibitors secreted by platelets. The inhibitor reacted with trypsin and possibly with urokinase but not with factor Xa.
 ...
PMID:Characteristics of a thrombin inhibitor secreted by activated platelets. 210 89

A low molecular weight serine protease inhibitor (TAP) was purified from extracts of the soft tick, Ornithodoros moubata. The peptide is a slow, tight-binding inhibitor, specific for factor Xa (Ki = 0.588 +/- 0.054 nM). The inhibitor also acts as an anticoagulant in several human plasma clotting assays in vitro. Its amino acid sequence (60 residues) has limited homology to the Kunitz-type inhibitors. However, unlike other inhibitors of this class, TAP inhibits only factor Xa. It had no effect at a 300-fold molar excess on factor VIIa, kallikrein, trypsin, chymotrypsin, thrombin, urokinase, plasmin, tissue plasminogen activator, elastase, or Staphylococcus aureus V8 protease. TAP's specificity and size suggest that it may have therapeutic value as an anticoagulant.
 ...
PMID:Tick anticoagulant peptide (TAP) is a novel inhibitor of blood coagulation factor Xa. 233 10

A highly selective inhibitor of plasma-kallikrein (PK), N-(trans-4-aminomethylcyclohexylcarbonyl)-L-phenylalanine 4-carboxymethyl-anilide hydrochloride, was designed and synthesized by the authors' group, called PKSI-527 in our laboratories. (I) PKSI-527 inhibited PK with a Ki value of 0.81 microM. By contrast, the Ki values for glandular kallikrein (GK), plasmin, thrombin, urokinase and factor Xa were greater than 500 microM, 390 microM, greater than 500 microM, 200 microM and greater than 500 microM, respectively. (II) Effects of PKSI-527 on bradykinin (BK) generation, coagulation and fibrinolysis by contact activation were examined using human plasma. (a) BK generation induced by kaolin appeared to be reduced by PKSI-527. Furthermore BK generation induced by lambda-carrageenan, a strong inflammatory agent, was also reduced by PKSI-527. (b) Partial thromboplastin time (PTT) was prolonged by PKSI-527, indicating the suppression of the intrinsic coagulation system. (c) Euglobulin clot lysis time (ECLT) of plasma which was shortened by activation with kaolin, was prolonged by the addition of PKSI-527, confirming the participation of PK in contact-fibrinolysis. These results indicate that PKSI-527 shows great potential in elucidating the significance of PK, and as such deserves further investigation.
 ...
PMID:Effect of a highly selective plasma-kallikrein synthetic inhibitor on contact activation relating to kinin generation, coagulation and fibrinolysis. 238 57

Parameters of the fibrinolytic system were studied in a primate model where the generation of thrombin was promoted in vivo. The procoagulant stimulus used was a combination of human factor Xa in combination with phosphatidylcholine/phosphatidylserine lipid vesicles (PCPS) as the source of coagulant active phospholipid. The dosage of each component was formulated to provide a gradation of thrombin generating potential assessed prior to in vivo study in an in vitro clotting assay. These ranged from 25.25-36.60 pMole/kg (factor Xa) and 18.85-56.30 nMole/kg (PCPS). In each case, the ratio of the dose of factor Xa/PCPS was maintained at 0.65 (pMole factor Xa/nMole PCPS). Individual dosage combinations producing recalcification clotting times in vitro of 15, 20, 25 and 30 s were used in detailed in vivo studies. Previous studies in dogs had confirmed the thrombin generating potential of factor Xa/PCPS infusions and demonstrated an associated activation of protein C and increased fibrinolytic activity. This has now been extensively characterized in the chimpanzee as follows: 10 min after the infusion of the highest dose (36.6 pMole factor Xa/56.3 nMole PCPS kg bodyweight), the level of circulating t-PA had risen to 900 ng/ml (antigen), 885 IU/ml (functional). Dosage was observed with the lowest dose of 12.25 pMole factor Xa and 18.85 nMole PCPS being associated with relatively minor increases in circulating t-PA activity. There were no changes in u-PA at any dosage during the full time course of the experimental period (90 min). Plasminogen activation was also apparent with alpha-2 antiplasmin levels falling to 30-40% of pre-infusion levels at the highest dosages.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The fibrinolytic potential of the normal primate following the generation of thrombin in vivo. 240 50

Plasma protein C inhibitor (PCI) was purified to homogeneity (greater than 95%) with good recovery (greater than 25%) and reproducibility, and the inhibition of a number of blood clotting and fibrinolytic enzymes by purified PCI was studied. PCI inhibited activated protein C (APC), two-chain urokinase (2c-uPA), two-chain tissue plasminogen activator (2c-tPA), thrombin, factor Xa, plasma kallikrein and factor XIa, and this inhibition was accelerated by heparin. The inhibition of each enzyme was accompanied by formation of enzyme inhibitor complexes and by degradation of the inhibitor to lower molecular weight derivatives. Plasma kallikrein and factor XIa cleaved PCI of native Mr = 57,000 into two products with Mr = 54,000 and 52,000 whereas the other enzymes converted the PCI to a product with Mr = 54,000. PCI did not detectably inhibit alpha-factor XIIa or plasmin. Kinetic studies using PCI yielded the following second-order rate constants for inhibition of human APC, 2c-uPA, 2c-tPA, thrombin, factor Xa, kallikrein and factor XIa respectively: 0.65 x 10(4), 0.22 x 10(4), 0.08 x 10(4), 0.61 x 10(4), 2.01 x 10(4), 6.50 x 10(4), and 9.03 x 10(4) M-1s-1 in the absence of heparin and 1.58 x 10(6), 0.43 x 10(6), 0.03 x 10(6), 0.52 x 10(6), 0.09 x 10(6), 0.18 x 10(6) and 0.74 x 10(6) M-1s-1 in the presence of optimal concentrations of heparin. The rate constants for the inhibition of factor XIa and 2c-uPA by PCI suggest a possible role of PCI in the physiologic regulation of these enzymes. The second order rate constants for inhibition of bovine APC and Gla-domainless bovine APC by human PCI were 0.61 x 10(4) and 0.26 x 10(4) M-1s-1 in the absence of heparin and 0.54 x 10(6) and 0.71 x 10(6) M-1s-1 in the presence of heparin, respectively. Calcium ions (0.05 to 4 mM) did not affect these rate constants. The results obtained with normal and Gla-domainless APC indicate that the Gla domain of APC is not required for inactivation by PGI and is not essential for the heparin stimulation of this reaction.
 ...
PMID:Purification and characterization of plasma protein C inhibitor. 255 Oct 64

We studied the effects of FR-860 on coagulative and fibrinolytic activities in human plasma compared to conventional unfractionated heparin (UF-heparin). Both FR-860 and UF-heparin dose-dependently prolonged the recalcification time, activated partial thromboplastin time, prothrombin time, factor Xa (F.Xa) clotting time and thrombin time. These effects of FR-860 were weaker than that of UF-heparin. FR-860 showed equipotent efficacy on the anti-F.Xa activity, and weak antithrombin activity compared to UF-heparin. FR-860 had no effects on the activity of ATIII and fibrinolytic activity. UF-heparin shortened the urokinase-activated euglobulin lysis time and showed antiplasmin activity, but did not influence the activities of ATIII, plasminogen and alpha 2-plasmin inhibitor. UF-heparin decreased the fibrinogen level at higher doses. These efficacies of FR-860 were weaker than that of UF-heparin. These results suggest that FR-860 is more efficient and lower in bleeding risk than UF-heparin in clinical use.
 ...
PMID:[Effects of low molecular weight heparin (FR-860) on coagulative and fibrinolytic activities]. 261 5

Glutamylglycinylarginyl chloromethyl ketone, tyrosylglycinylarginyl chloromethyl ketone, and phenylalanylprolylarginyl chloromethyl ketone have been labeled at their amino termini using fluorescein, rhodamine-X, lissamine-rhodamine, pyrene, and the 1,5-, 2,5-, and 2,6-dimethylaminonaphthalene-1-sulfonyl moieties. These peptidyl chloromethyl ketones have also been modified by incorporation of biotin and epsilon-amino caproyl biotin. The ability of these various chloromethyl ketones to be incorporated into a collection of zymogen-enzyme pairs has been evaluated using a variety of coagulation and fibrinolytic proteins. All labeled chloromethyl ketones were efficiently incorporated into the proteases tested, with the exception of urokinase which was refractory to inhibition by phenylalanylprolylarginyl chloromethyl ketone derivatives. No modification of any zymogen species was observed even under conditions designed to detect minimal reactivity. When enzymes were modified using chloromethyl ketones labeled with epsilon-amino caproyl biotin, the modified proteins readily reacted with avidin under a variety of different conditions. The observed reactivity with avidin was used in enzyme "blotting" following electrophoretic resolution of polypeptide chains and to remove active enzyme present in enzyme-zymogen mixtures. These reagents have been used to evaluate the potential for active site expression by the single-chain human factor VII molecule. Studies conducted with tissue factor, phospholipids, and calcium using factor X as substrate demonstrate that no activity can be obtained without initial activation of either factor X to factor Xa or factor VII to factor VIIa by an external source. We thus conclude that factor VII is a true zymogen, inert in the blood clotting process prior to its cleavage to factor VIIa.
 ...
PMID:Zymogen/enzyme discrimination using peptide chloromethyl ketones. 270 77

The inhibitory effect of the clinically used p-carbethoxyphenyl ester of epsilon-guanidino-caproic acid methanesulphonate (epsilon-GCA-CEP) on the catalytic properties of human LYS77-plasmin (EC 3.4.21.7), bovine factor Xa (EC 3.4.21.6), bovine alpha-thrombin (EC 3.4.21.5), ancrod (EC 3.4.21.28), crotalase (EC 3.4.21.30), bovine beta-trypsin (EC 3.4.21.4), porcine pancreatic beta-kallikrein-B (EC 3.4.21.35), human urinary kallikrein (EC 3.4.21.35) and the Mr 54,000 species of human urokinase (EC 3.4.21.31) was investigated (between pH 2.0 and 8.5, I = 0.1 M; T = 21 +/- 0.5 degrees C), and analyzed in parallel with that of the homologous derivative p-carbethoxyphenyl epsilon-amino-caproate hydro chloride (epsilon-ACA-CEP). On lowering the pH from 5.5 to 3.0, values of the apparent dissociation inhibition constant (Ki) for epsilon-GCA-CEP and epsilon-ACA-CEP interaction with the serine proteinases considered increase, reflecting the acidic pK-shift upon inhibitor binding of a single ionizing group. Over the whole pH range explored, (i) epsilon-GCA-CEP interacts with bovine factor Xa and bovine alpha-thrombin with an higher affinity than that observed for epsilon-ACA-CEP binding; (ii) both inhibitors associate to bovine beta-trypsin with the same affinity; and (iii) epsilon-ACA-CEP inhibits human Lys77-plasmin and the Mr 54,000 species of human urokinase with an higher affinity than that reported for epsilon-GCA-CEP association, thus reflecting the known enzyme primary specificity properties. However, the affinity of epsilon-ACA-CEP for ancrod, crotalase, porcine pancreatic beta-kallikrein-B and human urinary kallikrein, all of which preferably bind arginyl rather than lysyl side chains at the primary position of substrates and/or inhibitors, is paradoxically higher than that displayed by epsilon-GCA-CEP. By considering the amino acid sequences, the X-ray three-dimensional structures and/or the computer-generated molecular models of serine proteinase: inhibitor adducts, the observed binding behaviour of epsilon-GCA-CEP and epsilon-ACA-CEP to the enzymes considered has been related to the inferred stereochemistry of proteinase: inhibitor contact region(s).
 ...
PMID:Inhibition of serine proteinases by p-carbethoxyphenyl esters of epsilon-guanidino- and epsilon-amino caproic acid: thermodynamic and molecular modeling study. 272 72

Human plasma contains an inhibitor of activated protein C (APC) which is termed according to its function protein C inhibitor (PCI). High purification of functionally active PCI with a yield of 18% is achieved by an improved procedure consisting of 4 steps: precipitation by rivanol, fractionation with ammonium sulfate, ion-exchange chromatography on DEAE Sephacel and chromatography on dextran sulfate Sepharose. This purification results in the isolation of a homogeneous PCI which migrates in immunoelectrophoresis with the beta-globulins of human plasma and in SDS PAGE as one single band at Mr = 57,000 both under reducing and nonreducing conditions. The specific activity of the highly purified PCI was determined to be 226 units/mg, 1 unit being equivalent to the activity of 1 ml fresh human citrated plasma. PCI forms complexes with 1:1 stoichiometry (Ki: 1.4 x 10(-8) M) resulting in a loss of the amidolytic activity of APC as measured on Tos-Glu-Pro-Arg-pNA (S 2366). The inhibition rate of APC by PCI (k: 7.5 x 10(5) M-1 min-1) is significantly increased in the presence of 5 i.u./ml heparin (kH: 2.2 x 10(7) M-1 min-1). PCI also blocks the amidolytic activities of urokinase plasminogen activator (u-PA), thrombin and factor Xa on their chromogenic substrates in a heparin-dependent manner. According to the Ki-values measured for these reactions PCI is a noncompetitive inhibitor of these proteases. The Ki-values calculated do not differ significantly from those obtained for the inhibition of APC by PCI. Immunodepleted PCI-deficient plasma still contains an inhibitory activity against APC which, however, only slowly inactivates the amidolytic activity of APC and in a time and concentration-dependent manner. Addition of heparin has no influence on the inhibition rate. This finding suggests the existence of a second, heparin-independent PCI present in human plasma.
 ...
PMID:A new and simple isolation procedure for human protein C inhibitor. Evidence for a second inhibitor for activated protein C present in human plasma. 285 98

Incubation of HTC rat hepatoma cells with the synthetic glucocorticoid dexamethasone rapidly inhibits plasminogen activator (PA) activity secondary to the induction of a specific acid-stable inhibitor of plasminogen activation (Cwikel, B. J., Barouski-Miller, P.A., Coleman, P.L., and Gelehrter, T.D. (1984) J. Biol. Chem. 259, 6847-6851). We have further characterized this inhibitor with respect to its interaction with both urokinase and tissue plasminogen activator, and its protease specificity. The HTC PA inhibitor rapidly inhibits urokinase and tissue plasminogen activator with an apparent second-order rate constant of 3-5 x 10(7) M-1 X s-1. The inhibitor forms stable covalent complexes with both urokinase and tissue plasminogen activator, with which plasmin, trypsin, and factor Xa apparently do not compete. Complex formation is saturable and requires the active site of the PA. The mass of the inhibitor-PA complex is 50,000 daltons greater than that of PA alone, consistent with an Mr for the PA inhibitor of 50,000 as demonstrated directly by reverse fibrin autography. The HTC PA inhibitor does not inhibit thrombin and differs in its kinetic and biochemical properties from protease nexin.
 ...
PMID:Characterization of the dexamethasone-induced inhibitor of plasminogen activator in HTC hepatoma cells. 293 42


<< Previous 1 2 3 4 5 6 7 8 9 Next >>