Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: HUMANGGP:027518 (factor Xa)
 5,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The plasma of individuals, hetero- or homozygous for alpha1-antitrypsin deficiency, contains greatly decreased amounts of antithrombin activity as assayed against factor Xa. However, heparin stimulation of the residual antithrombin activity is observed, which is comparable to that of normal plasma. Antithrombins isolated from both normal and alpha1-antitrypsin deficient plasma by a simplified procedure are indistinguishable in both properties and yields. The microheterogeneity observed on isoelectric focusing of both preparations can be eliminated by treatment with neuraminidase. Neither purified human antithrombin nor alpha1-antitrypsin, when assayed against bovine trypsin, is stimulated by heparin. These results clearly establish the unique natures of antithrombin and alpha1-antitrypsin and show that about 75% of the antithrombin activity measured in normal plasma is due to alpha1-antitrypsin. Estimates of antithrombin III activity in normal plasma by assays dependent on enzymatic activity can probably be obtained only in the presence of heparin.
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PMID:Isolation of antithrombin III from normal and alpha1-antitrypsin-deficient human plasma. 30 58

The inactivation of thrombin and factor Xa by antithrombin was determined in the presence of heparin fractions of different molecular weights and with high affinity for antithrombin. The ability to potentiate the inactivation of either coagulation factor increased with increasing length of the polysaccharide chain.
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PMID:On the molecular-weight-dependence of the anticoagulant activity of heparin. 48 55

The factor Xa inactivating function of antithrombin III is measured automatically by an amidolytic method, adapted to a centrifugal analyser. Plasma is diluted in buffer with heparin. In stage I, diluted plasma is incubated with excess factor Xa. Heparin accelerates the saturation of antithrombin with factor Xa. In stage II, remaining factor Xa is determined with the chromogenic substrate Bz-Ile-Glu-Gly-Arg-pNA. The precision of the present assay compares favourably with that of the clotting assays and immunoassay. There is a close correlation (r = 0.82) between the results obtained with this assay and the immunoassay of antithrombin III.
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PMID:Automated antithrombin III assay with a centrifugal analyser. 65 85

Low-molecular-weight heparin subfractions more specifically inhibit factor Xa than thrombin, and they may have advantages over unfractionated heparin in arterial thrombosis. The antithrombotic efficacy of four dosages of a low-molecular-weight heparin (CY216 at 100, 200, 400, or 500 Institute Choay units/kg) was compared with unfractionated calcium heparin (100 US Pharmacopeia units/kg) and placebo during deep arterial injury produced by balloon dilatation of the carotid artery in the pig. The acute thrombotic end points were 111In-labeled platelet and 125I-labeled fibrinogen/fibrin deposition and macroscopic mural thrombosis; these were related to the anti-factor Xa and antithrombin effects of the heparin preparations. Platelet deposition in segments with deep arterial injury was 42 +/- 28, 22 +/- 5, 29 +/- 12, 9 +/- 2, 9 +/- 2, and 11 +/- 3 x 10(6)/cm2 (mean +/- SEM) for pigs treated with placebo, with 100, 200, 400, and 500 units/kg CY216, and with 100 units/kg unfractionated heparin, respectively. Fibrinogen/fibrin deposition was 35 +/- 8, 19 +/- 2, 19 +/- 4, 21 +/- 3, 14 +/- 4, and 12 +/- 3 molecules x 10(12)/cm2, respectively; deposition was significantly reduced in pigs given 100 units/kg unfractionated heparin compared with placebo (p less than 0.05). Mural thrombosis was present in 74%, 45%, 30%, 14%, 5%, and 9% of deeply injured arterial segments, respectively (p = 0.02). Plasma anti-factor Xa activity and prolongation of the activated partial thromboplastin time (aPTT) with 100 units/kg unfractionated heparin were similar to that produced by 200 units/kg and 500 units/kg CY216, respectively. Thus, low-molecular-weight heparin, which predominantly inhibits factor Xa activity, was only moderately effective at reducing platelet thrombus deposition. It was less effective than 100 units/kg unfractionated heparin, except at high dosages, producing similar prolongation of the aPTT and the thrombin time.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Antithrombotic efficacy of low-molecular-weight heparin in deep arterial injury. 131 47

Protein C inhibitor is a plasma protein whose ability to inhibit activated protein C, thrombin, and other enzymes is stimulated by heparin. These studies were undertaken to further understand how heparin binds to protein C inhibitor and how it accelerates proteinase inhibition. The region of protein C inhibitor from residues 264-283 was identified as the heparin-binding site. This differs from the putative heparin-binding site in the related proteins antithrombin and heparin cofactor. The glycosaminoglycan specificity of protein C inhibitor was relatively broad, including heparin and heparan sulfate, but not dermatan sulfate. Non-sulfated and non-carboxylated polyanions also enhanced proteinase inhibition by protein C inhibitor. Heparin accelerated inhibition of alpha-thrombin, gamma T-thrombin, activated protein C, factor Xa, urokinase, and chymotrypsin, but not plasma kallikrein. The ability of glycosaminoglycans to accelerate proteinase inhibition appeared to depend on the formation of a ternary complex of inhibitor, proteinase, and glycosaminoglycan. The optimum heparin concentration for maximal rate stimulation varied from 10 to 100 micrograms/ml and was related to the apparent affinity of the proteinase for heparin. There was no obvious relationship between heparin affinity and maximum inhibition rate or degree of rate enhancement. The affinity of the resultant protein C inhibitor-proteinase complex was also not related to inhibition rate enhancement, and the results showed that decreased heparin affinity of the complex is not an important part of the catalytic mechanism of heparin. The importance of protein C inhibitor as a regulator of the protein C system may depend on the relatively large increase in heparin-enhanced inhibition rate for activated protein C compared to other proteinases.
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PMID:Heparin binding to protein C inhibitor. 131 38

The purpose of this study was to compare three heparin-binding plasma proteinase inhibitors in order to identify common and unique features of heparin binding and heparin-enhanced proteinase inhibition. Experiments with antithrombin, heparin cofactor, and protein C inhibitor were performed under identical conditions in order to facilitate comparisons. Synthetic peptides corresponding to the putative heparin binding regions of antithrombin, heparin cofactor, and protein C inhibitor bound to heparin directly and interfered in heparin-enhanced proteinase inhibition assays. All three inhibitors obeyed a ternary complex mechanism for heparin-enhanced thrombin inhibition, and the optimum heparin concentration was related to the apparent heparin affinity of the inhibitor. The maximum inhibition rate and rate enhancement due to heparin appeared to be unique properties of each inhibitor. In assays with heparin oligosaccharides of known size, only the antithrombin-thrombin reaction exhibited a sharp threshold for rate enhancement at 14-16 saccharide units. Acceleration of antithrombin inhibition of factor Xa, heparin cofactor inhibition of thrombin, and protein C inhibitor inhibition of thrombin, activated protein C, and factor Xa did not require a minimum saccharide size. The differences in heparin size dependence and rate enhancement of proteinase inhibition by these inhibitors might reflect differences in the importance of the ternary complex mechanism and other mechanisms, alterations in inhibitor reactivity, and orientation effects in heparin-enhanced proteinase inhibition.
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PMID:A comparison of three heparin-binding serine proteinase inhibitors. 131 39

Three fractions of the low molecular weight heparin CY216 (fraxiparin, mean molecular weight [MMW] 5,090), with MMWs of respectively, 3,090, 4,400 and 7,910 were prepared by gel permeation chromatography. From CY222 (MMW 3,770) as well as from CY216 and its three fractions the material with high affinity to antithrombin III (AT III) was obtained by chromatography on immobilised AT III. The molecular weight distribution of each of the ten preparations thus obtained was determined by high performance liquid chromatography, while the content of AT III binding material was determined by stoichiometric titration of AT III, monitored by intrinsic fluorescence enhancement. We measured the effect of all heparins on the decay of endogenous thrombin in plasma and on the overall generation of thrombin in plasma, triggered via the extrinsic or via the intrinsic pathway. From these data we calculated the time course of prothrombin conversion, i.e. the course of factor Xa activity as expressed by prothrombinase activity. It was found that in platelet-poor plasma the anticoagulant properties of the heparins are largely dependent on their antithrombin action, which is determined by their content of high affinity material with a MW of 5,400 or higher. The specific antithrombin activity of all heparins, when expressed in terms of material with high affinity to antithrombin III (HAM) with a MW greater than 5,400 is 13.0 min-1/(microgram/ml) (range 10.5-15.9).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The mode of action of CY216 and CY222 in plasma. 131 16

The binding ability of low molecular weight heparin (FR-860), and conventional unfractionated heparin (UF-heparin) to factor Xa (F.Xa), thrombin and AT III was investigated using FR-860- and UF-heparin-Sepharoses. FR-860 could not bind directly to F.Xa. FR-860 bound to thrombin and AT III with stronger affinity to AT III than to thrombin. On the other hand, UF-heparin bound to F.Xa, thrombin and AT III with the strongest affinity to AT III followed by thrombin and F.Xa. AT III mediated the binding between F.Xa and FR-860 and accelerated the reaction between F.Xa and UF-heparin. On the other hand, AT III did not affect the binding between thrombin and FR-860 or UF-heparin. Diisopropyl fluorophosphate-treated thrombin inhibited the binding between AT III and FR-860, but not that between AT III and UF-heparin. These results suggest that the anti-F.Xa activity of FR-860 is mediated by AT III. Furthermore, the difference of antithrombin activity between FR-860 and UF-heparin depends on the capability to form ternary complex of FR-860 or UF-heparin, AT III and thrombin.
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PMID:Study of anticoagulant mechanism of low molecular weight heparin. 132 95

We have investigated the pharmacological properties of an O-acetylated butyryl derivative of the low molecular weight heparin CY 216 (C4-CY 216). In a purified system the ability of C4-CY 216 to catalyze thrombin and factor Xa inhibition was comparable to that of CY 216. The antithrombin and antifactor Xa catalytic efficiencies of C4-CY 216 were reduced 217 and 12 times respectively when albumin (10 mg ml-1) was added to the reagents, while those of CY 216 were essentially unchanged. In plasma, the antifactor Xa specific activity of C4-CY 216 was close to that of CY 216 but the antithrombin specific activity was 2 times lower. After bolus and continuous intravenous injection to rabbits, the clearances of the two activities of C4-CY 216 were on average half the corresponding values of CY 216. After subcutaneous injection, the bioavailability of C4-CY 216 was comparable to that of CY 216. C4-CY 216 was as potent as CY 216 in preventing venous thrombosis in the thromboplastin-Wessler model and the duration of the antithrombotic effect was longer than that of the parent compound. The chemical alteration of CY 216 did not enhance the prohaemorrhagic effect in the rat tail transection model. Therefore, the new concept of heparin derivative having a low clearance and long lasting effects that we have recently reported for unfractionated heparin may also be applied to a low molecular weight heparin.
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PMID:Pharmacological properties of a low molecular weight butyryl heparin derivative (C4-CY 216) with long lasting effects. 132 69

It is shown why the current practice of expressing heparin activity in International Units is not an adequate way to deal with the situation that arises after injection of low molecular weight heparins. An alternative approach is proposed. It is taken into account that the fraction of a low molecular heparin that binds with high affinity to antithrombin III contains two fundamentally different components: the material above the critical chain-length of 17 sugar units that has both anti-factor Xa activity and antithrombin activity (ACLM) and the material below that length with anti-factor Xa activity only (BCLM). It is shown how the levels of ACLM and BCLM in a plasma sample can be determined and expressed in micrograms/ml.
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PMID:A rational approach to heparins. 132 98


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