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

It has been found that dermatan polysulfates (DPS) I, II and III isolated from hagfish notochord, hagfish skin and shark skin, respectively, and chemically sulfated dermatan sulfate exhibit considerable anticoagulant activity in the "activated partial thromboplastin time (APTT)" system. On comparing the activities with the various compositions, including disaccharide units produced by the digestion with chondroitinase-ABC, it was shown that the activity of these dermatan polysulfates depends not only on the total sulfate content but also on the content of sulfated L-iduronic acid residues. The activity seemed to decrease for molecular weight of below 10,000. The effect of these dermatan polysulfates on th inactivation of the clotting enzymes, factor Xa and thrombin, by antithrombin II (AT-III) was also studied using chromogenic substrates for the assay of the enzyme activities. The dermatan polysulfates showed an inhibitory effect on thrombin-AT-III, as estimated by the APTT assay, in contrast with the effect on factor Xa-AT-III which was found to be very small.
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PMID:Anticoagulant activity of dermatan polysulfates. 680

Affinity-fractionated porcine heparin was randomly scissioned by chemical techniques to give hexasaccharides, octasaccharides, decasaccharides, and mucopolysaccharide fragments of approximately 14 residues and approximately 16 residues that were able to complex with the protease inhibitor. Direct measurements of the kinetic behavior of the hexasaccharides, octasaccharides, and decasaccharides showed that these fractions greatly enhanced the rate of Factor Xa inactivation by antithrombin. Indeed, these species exhibited specific molar activities that ranged from 6.9% (hexaccharide) to 60.9% (decasaccharide) of that of the heparin fragment of approximately 16 residues. However, these oligosaccharides exhibited essentially no ability to accelerate thrombin-antithrombin interactions. The avidity of the hexasaccharides, octasaccharides, and decasaccharides for the protease inhibitor increased as a function of size with the respective dissociation constants ranging from 5.5 X 10(-6) M to 2.9 X 10(-7) M. These data suggest that the region of the heparin molecule needed for catalyzing Factor Xa-antithrombin interaction is intimately related to the antithrombin binding domain. The smallest complex carbohydrate fragment that accelerated the inactivation of thrombin by antithrombin had approximately 14 residues. This fraction had an avidity for the protease inhibitor of 2.8 X 10(-7) M and specific molar activities of 140 units per mumol (thrombin neutralization) and 460 units per mumol (factor Xa inactivation). The largest heparin fragment examined contained approximately 16 residues. This fraction had an avidity for antithrombin of 2.4 X 10(-7) M and specific molar activities of 500 units per mumol (thrombin neutralization) and 560 units per mumol (Factor Xa inactivation). Detailed kinetic analyses showed that these two species are able to directly activate antithrombin to the same extent with respect to thrombin inhibition. However, the larger mucopolysaccharide fragment is also capable of approximating free enzyme with protease inhibitor.
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PMID:Multiple functional domains of the heparin molecule. 694 Jan 50

We have utilized circular dichroism spectroscopy to examine the interaction of antithrombin with heparin-derived oligosaccharides and mucopolysaccharides of various sizes. Our studies demonstrate that the various complexes exhibit two major types of chiral absorption spectra. The first of these patterns is seen when octasaccharide, decasaccharide, dodecasaccharide, or tetradecasaccharide fragments bind to the protease inhibitor. The circular dichroism spectra of these complexes when compared to the spectrum of free antithrombin show several distinguishing characteristics. On the one hand, there is a marked general increase in positive chiral absorption that is maximal at 296 and 288 nm and 290 and 282.5 nm. These observations indicate perturbation of "buried" and "exposed" tryptophan residues. On the other hand, a significant augmentation in circular dichroism that peaks at 269.5 and 263 nm is noted. These findings are probably due to the summed positive and negative contributions arising from tryptophan residue(s), disulfide bridge(s), and phenylalanine residue(s). Given that these heparin fragments are able to accelerate factor Xa-antithrombin interactions but not thrombin-antithrombin interactions, the above spectral transitions must be associated with either the binding of a critical domain of the oligosaccharides to the protease inhibitor or the "activation" of the protease inhibitor with respect to factor Xa neutralization. The second of these patterns is apparent when octadecasaccharide, low molecular weight heparin (6,500), and high molecular weight heparin (22,000) interact with antithrombin. The circular dichroism spectra of these complexes compared to the spectrum of free protease inhibitor are similar to the first pattern except for changes within the 292- to 282-nm and 275- to 255-nm regions. The subtraction of the first pattern from the second pattern reveals a shallow negative band between 300 and 275 nm with potential negative minima at 290 and 283 nm as well as a deep negative band between 275 and 255 nm with possible negative minima at 268 and 262 nm. This chiral absorption profile is most likely to arise from conformational changes of a disulfide bridge(s). However, we cannot completely exclude the possibility that the above circular dichroism difference curve might be explained on the basis of transitions originating from a tryptophan residue(s). Given our method for generating the above data, these spectral alterations must be associated with the binding of a second critical domain of the mucopolysaccharide to antithrombin that is required for rapid complex formation with thrombin or the activation of the protease inhibitor with respect to the neutralization of the latter enzyme.
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PMID:Circular dichroism spectroscopy of heparin-antithrombin interactions. 696 2

A mucopolysaccharide was isolated from mussel broth. After sulphation, an electrophoretically homogenous product was obtained with a molecular weight of approximately 40 000 daltons and a sulphur content of about 12%. The sulphated polysaccharide (S-Lim) displayed an anticoagulant activity in a thrombin test system with human plasma. Unlike heparin, the anticoagulant effect of S-Lim was observed also in a thrombin-fibrinogen clotting system in the absence of AT III. Complete inhibition of the effect of 1.0 mg S-Lim was achieved with 1.5 mg protamine. In an activated partial thromboplastin time test system the anticoagulant activity of 1.0 mg S-Lim corresponded to about 40 iu of heparin. S-Lim was also found to inhibit thrombin-induced platelet aggregation. Furthermore, S-Lim inhibited the thrombin-dependent activation of factor XIII in human plasma. S-Lim did not affect various tests systems measuring factor Xa activity. It is concluded that this new sulphated mucopolysaccharide acts as a pure antithrombin with a potency corresponding to 40--50 iu heparin/mg S-Lim. In contrast to heparin and other heparinoids it does not require the presence of AT III.
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PMID:A novel semi-synthetic sulphated polysaccharide with potent antithrombin activity. 705 22

Antithrombin III (AT-III) was isolated by heparin affinity chromatography from adult venous and newborn term and preterm umbilical cord blood. The purified proteins were compared by SDS-PAGE, rocket immuno-electrophoresis, protein concentration by microbiuret relative to optical density at 280 nm, heparin cofactor specific activity, progressive neutralization of thrombin and factor Xa at 37 degree C and pH related antithrombin kinetics. The structural evaluations revealed a fetal AT-III of molecular weight, charge and electrophoretic migration indistinguishable from adult AT-III. The functional studies showed that, on an equimolar basis, the rates of thrombin and Xa interactions with fetal AT-III were as rapid as those with adult AT-III. The catalytic rates of various concentrations of heparin were also equal. The newborn infant, therefore, displays a quantitative but not quantitative deficiency of AT-III.
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PMID:Biochemical and functional study of antithrombin III in newborn infants. 707 6

We have evaluated the efficacy of utilizing radioimmunoassays (RIAs) for prothrombin activation fragments (F2/F1 + 2) and for thrombin--antithrombin complex (TAT) in purified systems and in whole blood. During venipuncture, appropriate anticoagulants were employed in order to prevent the generation of thrombin and factor Xa. The RIAs were shown to be specific for F2/F1 + 2 as well as TAT and did not interact with other plasma components. Initially, thrombin generation was studied in a purified human system of prothrombin, antithrombin, factor Xa, and factor V as well as phospholipid and Ca++. Under these conditions, the kinetics of F2/F1 + 2 and TAT generation were virtually superimposable. However, when factor V was omitted from the reaction mixture, a significantly greater amount of F2/F1 + 2 as compared to TAT was observable. Subsequently, prothrombin activation was monitored during the spontaneous coagulation of freshly drawn blood. Throughout the entire course of thrombin generation, the observable rate of formation of F2/F1 + 2 was considerably greater than that of TAT. We have examined the levels of F2/F1 + 2 and TAT in normal individuals. Our studies indicate that the concentrations of F1 + 2 and TAT average 1.97 nM and 2.32 nM, respectively. We have also quantitated the concentrations of F2/F1 + 2 and TAT in patients with disseminated intravascular coagulation. In these individuals, the levels of both components are elevated. However, the ratio of F1 + 2 to TAT ranges from 2.37 to 5.55. Thus, we conclude that under in vivo conditions, prothrombin activation is characterized by the accumulation of a stable precursor, such as prethrombin-2, and that this phenomenon may be related to an alteration of factor V function.
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PMID:Studies of the prothrombin activation pathway utilizing radioimmunoassays for the F2/F1 + 2 fragment and thrombin--antithrombin complex. 707 14

In previous papers, we have described the preparation and heparin-like properties of insoluble modified polystyrene resins. We now report results about the interactions of several coagulation factors with some of these materials. Most of the non-activated factors are neither adsorbed nor modified, except factor V and prekallikrein. In contrast thrombin, antithrombin III and factor Xa adsorb on the surface of such insoluble polymers. Thrombin can be desorbed by addition of a polycationic compound. The inactivation of thrombin or factor Xa by antithrombin is catalysed by the presence in the mixture of these insoluble materials as it is with soluble heparin. The initial velocity of these reactions is second order for both types of catalysis-homogeneous or heterogeneous - as previously reported for soluble heparin. In the case of these insoluble materials, the inhibition of protease by antiprotease seems to be accelerated when complexes are formed between the polymer and the proteins.
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PMID:Interactions of anticoagulant insoluble modified polystyrene resins with plasmatic proteins. 715 29

Synthetic substrates have recently been developed for the assay of several of the proteolytic enzymes required for blood coagulation, One of these substrates, S-2238, is specific for thrombin and hence can also be used to measure antithrombin-heparin co-factor (AT-III). The thrombin remaining after neutralization by AT-III cleaves a chromophore, p-nitroaniline, from the substrate, which can then te quantified in a spectrophotometer. This new assay for AT-III inhibitory activity was evaluated for normal subjects and for patients who had certain pathologic conditions associated with reduced levels of AT-III. Results from this assay were compared with those from AT-III assays by Laurell immunoelectrophoresis (an immunologic method) and antithrombin inhibition of factor Xa (a biologic clotting method). The chromogenic assay using S-2238 was found to be sensitive, accurate, and easy to perform; its results for both normal subjects and patients correlated extremely well with those of the immunologic and factor Xa inhibition assays (r = 0.94-0.98). Measurement of AT-III using this synthetic substrate should be a valuable addition to routine assays in a clinical coagulation laboratory. These and future substrates may prove extremely useful for assays of factors involved in blood coagulation and fibrinolysis.
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PMID:Measurement of antithrombin III in normal and pathologic states using chromogenic substrate S-2238. Comparison with immunoelectrophoretic and factor Xa inhibition assays. 737 31

The antithrombin-dependent inhibition of prothrombinase, assembled at a macroscopic surface, was studied under flow conditions utilizing a tubular flow reactor that consists of a phospholipid-coated glass capillary. Prothrombinase activity was determined from steady-state rates of thrombin production upon perfusion with prothrombin and from factor Va-associated factor Xa activity present in the flow reactor. The prothrombinase density was maintained at a low level (0.03 fmol/cm2) to assure that the rate of thrombin production reflected the amount of prothrombinase present in the capillary. Perfusion of the flow reactor with antithrombin resulted in an exponential decrease of prothrombinase activity in time. The second order rate constant (8.5 x 10(4) M-1min-1) is comparable with the rate of inactivation of free factor Xa. Inhibition was much faster when antithrombin was complexed with heparin. The second order rate constants of inhibition decreased with decreasing heparin chain length: 9.6 x 10(7), 4.5 x 10(7) and 0.39 x 10(7) M-1min-1 for unfractionated heparin, low molecular weight heparin and synthetic pentasaccharide heparin, respectively. In the presence of prothrombin (0.2 microM), however, the heparin-dependent rate of inhibition of prothrombinase was about 50-fold lower. The heparin-independent inhibition of prothrombinase by antithrombin (4 microM) in the presence of prothrombin (0.2 microM) was virtually negligible. At a 70-fold higher surface density of prothrombinase (2 fmol/cm2) prothrombinase activity was much faster inactivated. The rate of thrombin production, however, was not affected. In conclusion, at low prothrombinase densities, prothrombin efficiently protects prothrombinase from inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of prothrombinase by antithrombin-heparin at a macroscopic surface. 749 73

Orgaran is a LMW heparinoid composed of heparan sulphate (83% w/w) of which 4-5% has high affinity for antithrombin, dermatan sulphate (12% w/w) and chondroitin sulphate (5% w/w). To examine the contribution of the low-affinity fraction to Orgaran's antithrombotic activity we have quantitated the binding of plasma proteins to Orgaran and its component fractions in whole, hirudin-anticoagulated human plasma. Antithrombin, largely bound to the high-affinity fraction, and histidine-rich glycoprotein, interacting with low-affinity components, were the dominant proteins bound to Orgaran. Vitronectin, fibrinogen, fibronectin, heparin cofactor II, and apolipoprotein B were also detected in small amounts. The ratio of bound antithrombin, histidine-rich glycoprotein and vitronectin to GAG was negatively correlated with the Orgaran concentration in plasma, implying that the efficacy of Orgaran may not be linearly related to dose. Binding of antithrombin to the high-affinity fraction was not decreased by other plasma proteins or affected by addition of low-affinity material. Moreover, the antithrombin and anti-factor Xa activities of the high-affinity material were unaltered by low-affinity GAGs. On the basis of our results we conclude that the low-affinity material does not contribute to the antithrombotic activity of Orgaran by binding non-anticoagulant plasma proteins and releasing the high-affinity chains to interact with antithrombin and its target proteinases.
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PMID:Low-affinity material does not contribute to the antithrombotic activity of Orgaran (Org 10172) in human plasma. 752 81


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