Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The possibility that platelet activation may also involve membrane (Na-K)ATPase was investigated by testing the effects of both proteinases on platelet shape change and aggregation in the absence and presence of the specific (Na-K)ATPase inhibitor ouabain. Ouabain (8 to 80 microM) completely antagonized trypsin-induced platelet shape change and aggregation when it was preincubated with platelet suspension before the addition of trypsin. Unlike trypsin, thrombin-induced platelet activation was significantly enhanced by ouabain. It was also observed that on partially purified beef heart (Na-K)ATPase preparation, thrombin significantly enhanced the enzyme inhibition caused by submaximal inhibitory concentrations of ouabain. Soybean trypsin inhibitor (4 micrograms/ml) employed as the agent capable to counteract proteinase effects on the (Na-K)ATPase, was shown both to prevent and antagonize the platelet activation induced by trypsin (0.3 to 1.5 micrograms/ml), but it failed to modify the responses evoked by thrombin. It is concluded that membrane (Na-K)ATPase is involved differently in platelet activation by trypsin and thrombin probably because receptor sites to which either proteinase on the platelet surface binds, are distinct. Direct enzyme involvement is indeed apparent only in trypsin-induced platelet activation.
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PMID:Differential involvement of membrane (Na-K)ATPase in thrombin- and trypsin-mediated platelet activation. 132 84

X-ray diffraction studies of human thrombin revealed that compared with trypsin, two insertions (B and C) potentially limit access to the active site groove. When amino acids Glu146, Thr147, and Trp148, adjacent to the C-insertion (autolysis loop), are deleted the resulting thrombin (des-ETW) has dramatically altered interaction with serine protease inhibitors. Whereas des-ETW resists antithrombin III inactivation with a rate constant (Kon) approximately 350-fold slower than for thrombin, des-ETW is remarkably sensitive to the Kunitz inhibitors, with inhibition constants (Ki) decreased from 2.6 microM to 34 nM for the soybean trypsin inhibitor and from 52 microM to 1.8 microM for the bovine pancreatic trypsin inhibitor. The affinity for hirudin (Ki = 5.6 pM) is weakened at least 30-fold compared with recombinant thrombin. The mutation affects the charge stabilizing system and the primary binding pocket of thrombin as depicted by a decrease in Kon for diisopropylfluorophosphate (9.5-fold) and for N alpha-p-tosyl-L-lysine-chloromethyl ketone (51-fold) and a 39-fold increase in the Ki for benzamidine. With peptidyl p-nitroanilide substrates, the des-ETW deletion results in changes in the Michaelis (Km) and/or catalytic (kcat) constants, worsened as much as 85-fold (Km) or 100-fold (kcat). The specific clotting activity of des-ETW is less than 5% that of thrombin and the kcat/Km for protein C activation in the absence of cofactor less than 2%. Thrombomodulin binds to des-ETW with a dissociation constant of approximately 2.5 nM and partially restores its ability to activate protein C since, in the presence of the cofactor, kcat/Km rises to 6.5% that of thrombin. This study suggests that the ETW motif of thrombin prevents (directly or indirectly) its interaction with the two Kunitz inhibitors and is not essential for the thrombomodulin-mediated enhancement of protein C activation.
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PMID:Interaction of thrombin des-ETW with antithrombin III, the Kunitz inhibitors, thrombomodulin and protein C. Structural link between the autolysis loop and the Tyr-Pro-Pro-Trp insertion of thrombin. 132 50

Thermodynamic parameters for the binding of hirudin to human alpha, beta and gamma-thrombin have been determined between pH 5.0 and 9.0, and from 10 degrees C to 40 degrees C; kinetic data for the association and dissociation of the proteinase-inhibitor complex were obtained at pH 7.5 and 21 degrees C. These results have been analysed in parallel with the inhibitor-binding properties of human alpha, beta and gamma-thrombin for the bovine basic pancreatic trypsin inhibitor (Kunitz-type inhibitor; BPTI). For the purpose of an homogeneous comparison, values of the apparent association equilibrium constant for BPTI binding to human gamma-thrombin have been determined between pH 5.0 and 9.0, at 21 degrees C. The different binding behaviour of hirudin and BPTI with respect to human alpha, beta and gamma-thrombin has been related to the inferred stereochemistry of the proteinase-inhibitor contact regions. In particular, whereas the beta and gamma-loops play an appreciable role in the stabilization of the enzyme-hirudin complexes, they contribute to impairment of the adduct formation for the proteinase/BPTI system.
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PMID:Binding of hirudin to human alpha, beta and gamma-thrombin. A comparative kinetic and thermodynamic study. 137 1

Plasma levels of von Willebrand factor (vWf) are frequently elevated in patients with disseminated intravascular coagulation (DIC). To investigate the qualitative abnormalities of vWf and the possibility of its ex vivo modification in DIC, we analysed the multimeric composition of vWf in citrated plasma from 15 patients with DIC in the presence or absence of serine protease inhibitors (aprotinin and soybean trypsin inhibitor) and/or cysteine protease inhibitors (leupeptin, N-ethylmaleimide and EDTA). The proportion of large vWf multimers in plasma prepared in the presence of cysteine protease inhibitors was higher than those without such inhibitors. The addition of serine protease inhibitors during the preparation of plasma had no effect on the relative amounts of large multimers. The relative proportion of large multimers in plasma prepared without inhibitors and the difference between plasmas prepared with and without cysteine protease inhibitors correlated with plasma plasmin-alpha 2-plasmin inhibitor complex values, but not with other plasma or serum markers of DIC (platelet count, fibrinogen, FDP, D-dimer or thrombin-antithrombin III complex). We conclude that ex vivo proteolysis of plasma vWf occurs frequently in patients with DIC and cysteine protease inhibitors can protect this degradation.
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PMID:Enhanced ex vivo proteolysis of plasma von Willebrand factor in disseminated intravascular coagulation. 145 Mar 24

A metalloprotease from the rattlesnake Crotalus atrox venom was isolated and purified from multiple-step chromatographies including anion-exchange chromatography, gel permeation and reversed-phase HPLC. The fraction was shown to be homogeneous as judged by SDS-gel electrophoresis. It also showed a high proteolytic activity against alpha- and beta-chains of fibrinogen molecules. Further characterization of the purified fraction with fibrinogenase activity indicated that it is a single-chain protease with a molecular mass of about 24 kDa and an acidic isoelectric point. It is relatively heat stable up to about 65 degrees C, inhibited by EDTA, beta-mercaptoethanol, but not by phenylmethanesulfonyl fluoride, N alpha-p-tosyl-L-phenylalanine chloromethyl ketone and N alpha-p-tosyl-L-lysine chloromethyl ketone, soybean trypsin inhibitor and aprotinin. Amino acid analysis showed that the enzyme possesses an amino acid composition very similar to some metalloproteases characterized before from the closely related rattlesnake venoms. N-Terminal sequence analysis of the enzyme corroborated some similarity between this enzyme and the reported sequences of these enzymes characterized from the Crotalidae snake family. This study indicated the presence of a novel fibrinogenase (termed Catroxase) with N-terminal sequence different from the metalloprotease with hemorrhagic activity isolated from the same Western diamondback rattlesnake.
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PMID:Characterization of a protease with alpha- and beta-fibrinogenase activity from the Western diamondback rattlesnake, Crotalus atrox. 152 Mar 24

Recent work has suggested that the thrombin-bound conformation of fibrinopeptide A exhibits a strand-turn-strand motif, with a beta-turn centered at residues Glu-11 and Gly-12. Our molecular modeling analysis indicates that the published fibrinopeptide conformation cannot bind reasonably to thrombin but that reorientation of two residues by alignment with bovine pancreatic trypsin inhibitor provides a good fit within the deep thrombin cleft and satisfies all of the experimental nuclear Overhauser effect data. Based on this analysis, we have successfully designed and synthesized hybrid peptide mimetic substrates and inhibitors that mimic the proposed beta-turn structure. The results indicate that the turn conformation is an important aspect of thrombin specificity and that our turn mimetic design successfully mimics the thrombin-bound conformation of fibrinopeptide.
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PMID:Peptide mimetics of the thrombin-bound structure of fibrinopeptide A. 154 64

Venom toxins were isolated from rattlesnake (Crotalus atrox) venom by cation-exchange chromatography. Seven major fractions could be obtained by single-step ion-exchange chromatography with two fractions showing essentially apparent homogeneity by SDS-gel electrophoresis. All fractions showed various extents of specific proteolytic activity against alpha- or beta-chains of fibrinogen molecules. Further characterization of one of the purified fractions with alpha-fribrinogenase activity indicated that it is a single-chain thrombin-like protease with a molecular mass of about 30 kDa. It is relatively heat stable, inhibited by phenylmethanesulfonyl fluoride, N alpha-p-tosyl-L-phenylalanine chloromethyl ketone and N alpha-p-tosyl-L-lysine chloromethyl ketone but not by soybean trypsin inhibitor and beta-mercaptoethanol. Amino acid analysis showed that the enzyme possesses an amino acid composition very similar to thrombin and crotalase characterized before from the closely related snake venoms. N-Terminal sequence analysis of the enzyme corroborated the close similarity between this enzyme and those sequences of crotalase and kallikrein-like enzymes characterized from the same Crotalidae snake family. This study is in contrast to the previous reports which indicated a lack of thrombin- and crotalase-like enzyme in the venom of Western diamondback rattlesnake.
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PMID:Isolation of a crotalase-like protease with alpha-fibrinogenase activity from the western diamondback rattlesnake, Crotalus atrox. 161 87

Protease nexin I (PNI), a 43,000- to 50,000-dalton glycoprotein, is a potent thrombin and urokinase inhibitor produced by many mammalian cells, including human glia, in tissue culture. PNI is a member of the growing superfamily of serine protease inhibitors now known as serpins, but, unlike many others of this family, it has not yet been detected in normal human plasma. Of interest to neurobiology and neurologic disease, PNI is identical to a glia-derived neurite-promoting factor, glia-derived nexin (GDN). Antibody to PNI stains the periphery of senile amyloid plaques in brain tissue from patients with Alzheimer's disease (AD), along with another serpin, alpha 1-antichymotrypsin (alpha 1-ACT). A soluble form of the beta-amyloid precursor protein (beta APP), containing a Kunitz-type trypsin inhibitor domain, the beta APP751 form, is identical to protease nexin II (PNII), a 100,000-dalton serine protease inhibitor present in a number of tissues besides the brain. PNII/beta APP is also found in normal and AD CSF. We found a 47,000-dalton PNI, a thrombin- and urokinase-inhibiting serpin, in normal human CSF by Western blotting using a monospecific antibody. We also demonstrated biologically active PNI capable of forming complexes with serine proteases 125I-urokinase or 125I-thrombin.
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PMID:Protease nexin I, thrombin- and urokinase-inhibiting serpin, concentrated in normal human cerebrospinal fluid. 162 Mar 46

Hirudin is a potent and specific thrombin inhibitor. Since recombinant hirudin is being considered for anticoagulant and antithrombotic therapy we developed a fast and sensitive chromogenic substrate assay for its determination in plasma. The plasma samples (20 microliters) were incubated with 1 ml reagent mixture (0.2 M Tris buffer, 0.025 M NaCl, pH 8.1, containing 0.833 M urea, 0.7 trypsin inhibitor U/ml aprotinin, 100 ng/ml Polybrene and 0.31 NIH U/ml bovine thrombin) for 1 min. Thereafter 100 microliters Chromozym TH (Tos-Gly-Pro-Arg-pNA, 1.9 mM) was added. The change in absorbance/min (delta A/min) was recorded at 405 nm. delta A/min was linear for at least 3 min. The calibration curve was linear at least up to 800 ng hirudin/ml plasma. Intra-assay and inter-assay coefficients of variation were 2.8-3.1% and 5.3-5.8% respectively. The influence of progressive thrombin inhibitors can be neglected because of the short incubation time. Plasma samples can be assayed directly if aprotinin, polybrene and urea are added to the reagent mixture.
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PMID:Development of a chromogenic substrate assay for the determination of hirudin in plasma. 177 79

A fraction separated from rat submandibular gland homogenates was found to contain a potent vasoconstrictor when tested on isolated rabbit aortic rings. The vasoconstrictor was purified by a series of chromatographic steps. The purified compound (2.77 x 10(-9) M) induced 40% of the maximum contractile response to 60 mM KCl. Constriction was slow in onset, long-lasting, rinse-resistant, and unchanged by de-endothelialization; in addition, it was dose-related and inhibited by both EGTA and verapamil, but it was not affected by DUP753, an angiotensin II receptor antagonist. The compound was found to be a protein having a pI of 7.36 and a molecular weight of approximately 29,000 and exhibiting partial immunologic identity to rat glandular kallikrein and rat tonin. After 2-mercaptoethanol treatment, it separated into heavy (approximately 19,900) and light (approximately 10,700) chains having amino-terminal sequences of AY(X)HNNDLMLL and VVGGYN(X)ETNSQ, respectively. We found that they correspond to the amino-terminal and internal sequence of a previously unidentified kallikrein-like serine protease whose mRNA, named S3, has been found in the rat submandibular gland and prostate. The vasoconstrictor is able to hydrolyze t-butoxycarbonyl-valine-proline-arginine-methylcoumarin amide (a thrombin substrate), although its Kcat/Km was only 0.02% that of rat thrombin. Both vasoconstrictor and enzymatic activity on t-butoxycarbonyl-valine-proline-arginine-methylcoumarin amide were completely suppressed by amidinophenylmethylsulfonyl fluoride and soybean trypsin inhibitor; however, they were unaffected by hirudin, a thrombin inhibitor. At pH 6.5, it released angiotensin II when incubated with sheep angiotensinogen, although it had approximately one-tenth the activity of tonin. The submandibular enzymatic vasoconstrictor is a kallikrein-like enzyme, having some properties of both tonin and thrombin. It directly contracts vascular smooth muscle, acting via a mechanism that requires intact enzymatic activity.
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PMID:A novel serine protease with vasoconstrictor activity coded by the kallikrein gene S3. 190 May 13


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