Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.2.7 (heparinase)
 1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It had been suggested that antithrombin activity on the surface of intact endothelial cells may play a role in inhibiting platelet adhesion and thrombus formation. The antithrombin activity may be due to thrombomodulin or to activation of antithrombin III by glycosaminoglycans or thrombomodulin, or possibly a combination of these. This inhibitory activity has been shown to be affected by such antiheparin agents as protamine, hexadimethrine bromide (Polybrene; Aldrich Chemical Co., Milwaukee, Wis.) and platelet factor 4, as well as by such enzymes as heparinase and heparitinase. We have used a hamster cheek pouch preparation to observe thrombus formation in vivo in a normal vascular flow, to determine whether the production of thrombi by thrombin can be enhanced by antiheparin agents. After intra-arterial injection or topical application of protamine or hexadimethrine bromide, platelet adhesion and thrombus formation on intact arteriolar endothelium was produced by a dose of thrombin, which when injected alone had no effect. No thrombi were found in venules or capillaries. Injection of heparin before or after the antiheparin agents necessitated a larger dose to enhance the action of thrombin. On electron microscopy the thrombi were found to consist primarily of platelets adherent to an intact endothelium. The possible clinical implications of these observations are discussed.
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PMID:Production of thrombi on intact endothelium by use of antiheparin agents in vivo. 224 59

A significant amount of anticoagulant substance was released along with histamine, when human lung mast cells were stimulated with anti-IgE and Ca-ionophore A23187. Its activity was lost by heparinase, not by chondroitin-ABC lyase or chondroitin-AC lyase, and also inhibited by Polybrene, suggesting it would be heparin.
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PMID:Anticoagulant substance released from human lung mast cells by stimulation with anti-IgE or Ca-ionophore A23187. 243 4

Thrombomodulin isolated from rabbit lung was separated by ion-exchange chromatography on DEAE-cellulose into a retarded (acidic) and a nonretarded (nonacidic) fraction. Both fractions contained the cofactor required for the activation of protein C. In addition, the acidic fraction (but not the nonacidic fraction) prevented the clotting of fibrinogen by thrombin ("direct" anticoagulant activity) and accelerated the inhibition of thrombin by antithrombin (effect corresponding to 2-10 international units of heparin per mg of protein). Both of these activities were readily neutralized by the synthetic polycation Polybrene, which did not appreciably affect protein C activation. They were also eliminated by digestion of thrombomodulin with bacterial heparinase, which, in addition, converted the acidic form of the protein C activation cofactor to a nonacidic form. Similar conversion observed during storage of thrombomodulin was attributed to endogenous proteinase activity. Density-gradient centrifugation of the acidic form of thrombomodulin in CsCl/4M guanidinium chloride failed to separate either of the direct or antithrombin-dependent anticoagulant activities from the protein C activation cofactor, which showed a buoyant density of 1.31-1.34 g/ml. The nonacidic cofactor had a lower density, 1.26-1.28 g/ml. Unreduced thrombomodulin yielded two major fractions of protein C activation cofactor on NaDodSO4/PAGE, with apparent Mr of approximately 68,000 and 57,000, respectively. The larger component contained essentially all of the direct and antithrombin-dependent anticoagulant activities. We propose that these activities as well as the negative charge and the higher buoyant density of the acidic, Mr 68,000 form of thrombomodulin are due to a heparin-like polysaccharide and, further, that this component can be separated from the major portion of the molecule, which contains the protein C activation site, through the action of a proteinase.
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PMID:Functional domains of rabbit thrombomodulin. 301 29

In a previous paper, we demonstrated that deep hypothermia in dogs provokes a release of a heparin-like factor. In the present study, we investigated some properties of this anticoagulant activity and compared it with exogenous heparin activity. The endogenous anticoagulant inhibited factors IIa and Xa; it was hydrolysed by heparinase and was AT III dependent. However, it differed from heparin in so far as it was adsorbed on cation exchange gel at neutral pH, its inhibition was decreased in the presence of neuraminidase, and it could not be neutralized with Polybrene or protamine. A release of heparan sulphate is suggested but remains to be demonstrated.
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PMID:Characterization of a heparin-like activity released in dogs during deep hypothermia. 314 96

Dermatan sulphate does not catalyse the inactivation of factor Xa. However, the low molecular weight (LMW) dermatan sulphate Desmin 370 has been shown to generate circulating anti-Xa activity following administration to humans. Using a single batch of Desmin 370, we measured 3 U/mg of anti-Xa activity by amidolytic assay in vitro. The material responsible for this activity had a lower molecular weight range (6000 and 1800 Da) than Desmin 370 and was more highly sulphated than the bulk of the drug. Heparinase digestion of Desmin 370 eliminated 90% of the in vitro anti-Xa activity without significantly interfering with its ability to potentiate inactivation of thrombin by HCII, suggesting that the anti-Xa activity is not due to dermatan sulphate and is probably heparin. When 125I-labelled Desmin 370 together with 40 mg/kg carrier drug was administered intravenously to a rabbit, anti-Xa activity was readily detectable in the plasma for up to 10 h and had a longer half-life than the sulphated radiolabel. Most of this anticoagulant activity was recovered from the plasma by Polybrene affinity chromatography and was probably a sulphated glycosaminoglycan. Administration of the heparinase-digested drug to a rabbit resulted in 70% less anti-Xa activity than the undigested drug. We conclude that Desmin 370 contains detectable quantities of biologically active low molecular weight heparin, which is responsible for persistent anti-Xa activity following intravenous administration.
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PMID:Low molecular weight heparin is responsible for the anti-Xa activity of Desmin 370. 881 78

Hexadimethrine bromide was used for the neutralization of heparin during cardiac surgery in the late 1950s. For some years, this institution has used it for patients who may be allergic to protamine. In view of the recent renewal of interest in hexadimethrine, we present four cases outlining its use during cardiac procedures in such patients. Other drugs for reversing the action of heparin such as heparinase or platelet factor IV are not yet widely available.
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PMID:Recent experiences with hexadimethrine for neutralizing heparin after cardiopulmonary bypass. 1038 67

Non-infectious, envelope protein-free, retrovirus-like particles (VLP) derived from either Moloney murine leukemia virus (MLV) or human HIV are able to bind efficiently to, but not infect, target cells. Upon subsequent addition to the bound particles of the G protein of vesicular stomatitis virus (VSV-G), an efficient surrogate retrovirus envelope protein, the VLP are efficiently taken up by the cells to produce infection. Cell attachment of the VLP is efficiently inhibited by soluble heparin and dextran sulfate and less efficiently abrogated by several other glycosaminoglycans (GAGs) including chondroitin sulfate A and chondroitin sulfate B (dermatan sulfate), as determined by deconvolution microscopic immunodetection of the viral gag protein and by quantitative binding studies of metabolically labeled (35)S-VLP. Enzymatic digestion of heparan sulfate (HS) from the cell surface with heparinase I also reduces VLP binding. Furthermore, VLP adsorption onto several CHO cell lines variably deficient in cell surface GAG is significantly but incompletely abrogated. De-sulfated heparins are less efficient than native heparin in inhibiting the Polybrene-mediated binding of VLP, whereas growth of human cells in the presence of sodium chlorate leads to significant reduction of Polybrene-mediated VLP binding. In addition, specific inhibition of VLP binding and infectivity of mature infectious VSV-G-pseudotyped virus is observed in the presence of heparin and HS under Polybrene-free conditions. We conclude from these studies that the presence of Polybrene, the degree of sulfation of cell surface GAG, and possibly the presence of charged cell surface macromolecules create an electrostatic environment that promotes optimum binding of VLP to cells. Additionally, our results demonstrate that, in the absence of Polybrene, initial attachments of non-infectious, envelope protein-free VLP and probably mature infectious virus particles are mediated by interactions of the virus particles with cell surface heparan sulfate, and possibly with other GAG molecules.
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PMID:Cell surface heparan sulfate is a receptor for attachment of envelope protein-free retrovirus-like particles and VSV-G pseudotyped MLV-derived retrovirus vectors to target cells. 1199 44