Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.37 (neutrophil elastase)
 4,078 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Total proteolytic activity (PA) is increased in the circulation of pediatric burn patients. The extent of the increase correlates with the percent total body surface area (TBSA) burned and is associated with increased susceptibility to fatal infection. To determine the source or sources of this PA, three factors were evaluated: (1) levels of proteinase inhibitors--antithrombin, alpha 2-antiplasmin, and alpha 1-proteinase inhibitor; (2) levels of proteinase--neutrophil elastase; and (3) activation of circulating proteolytic cascade systems as indicated by changes in levels of system components--plasminogen and prekallikrein. All assays measured functional levels of the proteins. Normal levels were determined in 25 consecutive well children who were seeing their pediatrician for checkups (14 boys, 11 girls, ranging in age from 10 months to 17 years). Twenty-five consecutive burn victims admitted to the Shriners Burns Institute, Cincinnati Unit (19 boys, six girls, aged 10 months to 17 years), with a mean full-thickness burn of 43.2% TBSA (range, 6%-87%) were studied in the first week postburn. Antithrombin, alpha 2-antiplasmin, plasminogen, and prekallikrein levels decreased (p < 0.001) postburn, whereas elastase increased (p < 0.001). We conclude that, in pediatric burn patients, decreased proteinase inhibitors, increased proteinase, and activation of circulating proteinase cascades all contribute to elevated total circulating PA postburn.
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PMID:Components of the increased circulating proteolytic activity in pediatric burn patients. 147 19

The heparin affinity of normal and two P1 variants of antithrombin-III (AT) was studied by gradient elution with NaCl in Tris buffer on heparin-Sepharose. At pH 7.4 normal AT eluted at [Na+] 0.78 mol/l and the variants both showed increased affinity with AT Pescara eluting at [Na+] 0.86 mol/l and AT Glasgow at [Na+] 0.92 mol/l. We have earlier proposed a model for heparin activation in which the native state of AT maintains a salt bridge involving the P1 Arg-393 residue. Binding of heparin induces a higher heparin affinity conformation in which the salt bridge is disrupted to reveal the reactive centre for inhibition of thrombin. The Glasgow and Pescara variants, lacking a reactive centre P1 basic residue, would be unable to form this salt bridge, and we suggested that the high affinity conformation which they adopt as their native state would resemble the heparin induced conformation. To examine this model, we measured the heparin induced fluorescence of two P1 variants and tested the susceptibility of their reactive loops to catalytic cleavage. Both variants had fluorescence spectra indistinguishable from normal AT. In the absence of heparin, neither variant was more susceptible than normal to catalytic cleavage by human neutrophil elastase. These findings suggest that the conformation of these P1 variants is different to that of fully heparinized normal AT.
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PMID:P1 variant antithrombins Glasgow (393 Arg to His) and Pescara (393 Arg to Pro) have increased heparin affinity and are resistant to catalytic cleavage by elastase. Implications for the heparin activation mechanism. 201 15

Human neutrophil elastase catalyzes the inactivation of antithrombin by a specific and limited proteinolytic cleavage. This inactivation reaction is greatly accelerated by an active anticoagulant heparin subfraction with high binding affinity for antithrombin. A potentially complex reaction mechanism is suggested by the binding of both neutrophil elastase and antithrombin to heparin. The in vitro kinetic behavior of this system was examined under two different conditions: 1) at a constant antithrombin concentration in which the active anticoagulant heparin was varied from catalytic to saturating levels; and 2) at a fixed, saturating heparin concentration and variable antithrombin levels. Under conditions of excess heparin, the inactivation could be continuously monitored by a decrease in the ultraviolet fluorescence emission of the inhibitor. A Km of approximately 1 microM for the heparin-antithrombin complex and a turnover number of approximately 200/min was estimated from these analyses. Maximum acceleratory effects of heparin on the inactivation of antithrombin occur at heparin concentrations significantly lower than those required to saturate antithrombin. The divergence in acceleratory effect and antithrombin binding contrasts with the anticoagulant functioning of heparin in promoting the formation of covalent antithrombin-enzyme complexes and is likely to derive from the fact that neutrophil elastase is not consumed in the inactivation reaction. A size dependence was observed for the heparin effect since an anticoagulantly active octasaccharide fragment of heparin, with avid antithrombin binding activity, was without effect on the inactivation of antithrombin by neutrophil elastase. Despite the completely nonfunctional nature of elastase-cleaved antithrombin and the altered physical properties of the inhibitor as indicated by fluorescence and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the inactivated inhibitor exhibited a circulating half-life in rabbits that was indistinguishable from native antithrombin. These results point to an unexpected and apparently contradictory function for heparin which may relate to the properties of the vascular endothelium in pathological situations.
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PMID:Inactivation of human antithrombin by neutrophil elastase. Kinetics of the heparin-dependent reaction. 273 32

In certain thrombotic states, large declines in the levels of functional circulating antithrombin occur, which may reflect the highly active nature of the endothelial surface in suppressing excessive amounts of activated coagulation enzymes. Alternatively, we have recently observed an unexpected and paradoxical in vitro functioning of heparin that could result in the inactivation of antithrombin in pathologic conditions. Specifically, antithrombin was rendered nonfunctional as an inhibitor of clotting enzymes as a result of a limited, heparin-dependent cleavage by neutrophil elastase. This inactivation occurred only in the presence of the active anticoagulant heparin fraction, which suggested that the heparin-antithrombin complex was the substrate for elastase attack. Interestingly, neutrophil elastase was found to bind tightly to heparin and heparin-like materials. Neutrophil elastase has been previously linked to nonspecific proteinolysis occurring in inflammatory thrombotic reactions. This affinity of both antithrombin and elastase for heparin suggests a novel mechanism of potential specificity. An important component of this hypothesis is the localization of the elastase/antithrombin reaction away from the high circulating levels of elastase inhibitors. The proposed inactivation of antithrombin on the vascular surface would likely occur only in pathologic states associated with neutrophil sequestration and activation. Nevertheless, this mechanism could lead to a localized reversal of the nonthrombogenic nature of the endothelium and potentially lead to significant reductions of functional antithrombin in certain disease states.
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PMID:Antithrombin inactivation by neutrophil elastase requires heparin. 280 25

Septicemic/endotoxic-induced adult respiratory distress syndrome (ARDS) remains a major clinical problem. The present study was to determine in the E. coli endotoxemic sheep ARDS model the efficacy of combination prophylaxis with antithrombin-III (AT-III) and alpha 1-proteinase inhibitor (alpha 1-PI). We reasoned that 1) AT-III supplementation would ameliorate the endotoxin-induced coagulopathy, 2) alpha 1-PI supplementation would attenuate pulmonary damage caused by neutrophil elastase and inactivation of AT-III by neutrophil elastase, and 3) the therapeutic effects of this combination would be additive or synergistic. The typical increases in lung lymph flow microvascular permeability to protein, transvascular protein flow and transvascular protein clearance, and decrease in systemic arterial PO2 were prevented or significantly attenuated during 5 hours of endotoxemia by the AT-III/alpha 1-PI combination pretreatment. Limited efficacy was observed with AT-III pretreatment, and none was seen with alpha 1-PI alone. Results of this study demonstrate that combining AT-III and alpha 1-PI prophylaxis prevents or attenuates indices of ARDS during gram-negative endotoxemia and that this efficacy is due to a statistically significant synergism between AT-III and alpha 1-PI.
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PMID:Synergistic protection from lung damage by combining antithrombin-III and alpha 1-proteinase inhibitor in the E. coli endotoxemic sheep pulmonary dysfunction model. 305 31

Proteolytically modified forms of human antithrombin III have been prepared by reaction of native antithrombin with thrombin, human neutrophil elastase, or porcine pancreatic elastase. These forms have two chains disulfide linked and are of the same molecular weight as native antithrombin III. 1H NMR spectroscopy has been used to characterize these proteins and to compare them to one another and to native antithrombin III. The three modified proteins have very similar NMR spectra and histidine residues with identical pH titration parameters, and they undergo the same spectral changes upon binding heparin. They differ from native antithrombin III in all of these respects. In addition, the proteins are much more stable than native antithrombin III. The three modified proteins behave identically as a function of temperature; at 372 K, 44 K above the unfolding temperature for native antithrombin III, the proteins are still folded and possess approximately 70 unexchanged amide protons even after several hours. The unfolding of the heparin binding domain at low concentrations of deuteriated guanidine hydrochloride seen in native thrombin III is absent in the modified forms. It is concluded that the thrombin- and elastase-modified forms of antithrombin have identical structures when allowance is made for the slightly different sites of cleavage by the two types of elastase and by thrombin. This structure is very different from that of native antithrombin III.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Properties of thrombin- and elastase-modified human antithrombin III. 340 16

Heparin is an acceleratory cofactor for antithrombin, a circulating inhibitor of blood coagulation enzymes. The presence of heparin on blood vessel walls is believed to contribute to the nonthrombogenic properties of those surfaces. In apparent opposition to this function, heparin was found to greatly accelerate the in vitro inactivation of antithrombin by neutrophil elastase. Inactivation rates in solution were potentiated several hundredfold by specific heparin fractions with anticoagulant activity. Although the data suggest that a heparin-antithrombin complex is essential for the inactivation by elastase to occur, the enzyme itself interacts tightly with heparin. These results suggest a mechanism which, if operating in vivo, could lead to a localized neutralization of the anticoagulant function of heparin at the endothelial surface.
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PMID:Heparin promotes the inactivation of antithrombin by neutrophil elastase. 364 21

An old puzzle in protein biochemistry concerns the ready conversion of ovalbumin, by proteolysis, to the much more stable derivative, plakalbumin. Ovalbumin is now known to belong to the serpin superfamily, most of which are serine proteinase inhibitors. We report here studies of two such members of the family, the human plasma proteins alpha 1-antitrypsin and antithrombin, and show that they undergo a similar change in stability on selective proteolysis. This change, which is accompanied by a loss of inhibitory activity, can best be considered as an irreversible molecular transition from a native stressed (S) conformation, to a more ordered relaxed (R) form. The maintenance of the native S conformation, and hence the maintenance of inhibitory activity, is critically dependent on the integrity of an exposed loop of polypeptide. We propose that the susceptibility of this peptide loop to proteolytic cleavage gives it an incidental role as a physiological switch which allows the inactivation of individual inhibitors by specific proteolysis. The vulnerability of this exposed loop in each inhibitor also explains the pathological action of a number of venoms and toxins. In particular, the demonstration here of the cleavage of antithrombin, by leukocyte elastase, explains an observed change in blood coagulation that accompanies severe inflammation and which can result in fatal thrombosis.
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PMID:Plakalbumin, alpha 1-antitrypsin, antithrombin and the mechanism of inflammatory thrombosis. 387 43

Protein C inhibitor (PCI), antithrombin, and heparin cofactor II are members of the serine proteinase inhibitor (serpin) superfamily that inhibit proteinases at rates which increase in the presence of the glycosaminoglycan heparin. These studies were undertaken to understand how PCI activity is modulated by various substances that are found in or interact with the vascular endothelium/basement membrane. The effects of antithrombin-heparin, thrombomodulin, vitronectin and leukocyte elastase on PCI-thrombin and PCI-activated protein C (APC) interactions were investigated. Antithrombin, which does not inhibit APC but which does bind to heparin/heparan sulphate with higher affinity than PCI, caused only a small decrease in the inhibition rate of PCI-APC in the presence of unfractionated heparin. Thrombomodulin, a chondroitin sulphate-containing proteoglycan, accelerated PCI inhibition of thrombin and APC. PCI-thrombin in the presence or absence of heparin bound plastic absorbed vitronectin, but neither PCI alone nor PCI-APC bound. Vitronectin also decreased the inhibition rate of PCI-thrombin and PCI-APC in the presence of low concentrations of heparin. Leukocyte elastase proteolytically inactivated PCI in a reaction that was accelerated by heparin. Overall, these results indicate that PCI activity is modulated by these endothelial cell/basement membrane-based substances in similar ways as other heparin-binding serpins, especially antithrombin.
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PMID:Modulation of protein C inhibitor activity. 753 47

The effect of heparin on the inactivation rates of fibrin-bound plasmin, miniplasmin and neutrophil leukocyte elastase (PMN-elastase) by their plasma inhibitors was studied. While plasmin and miniplasmin bound to fibrin are not inactivated by antithrombin, heparin (800 nM) makes these enzymes available for the inhibitor; the second-order rate constant increases from zero to 1.3 x 10(3) M-1 s-1 and 3.3 x 10(3) M-1 s-1, respectively. Heparin slightly increases the rate of fibrin-bound enzyme inactivation by plasmin inhibitor. alpha 1-Protease inhibitor, on the other hand, is unable to inactivate plasmin or miniplasmin bound to fibrin and heparin has no facilitating effect. In the case of PMN-elastase, heparin (300 nM) further increases enzyme protection against alpha 1-protease inhibitor; the rate constant decreases from 41 x 10(3) M-1 s-1 to 23 x 10(3) M-1 s-1. alpha 2-Macroglobulin inhibits fibrin-bound miniplasmin and PMN-elastase with a second-order rate constant of 1.8 x 10(4) M-1 s-1 and heparin (300 nM) increases the rate insignificantly for miniplasmin and by a factor of two for PMN-elastase. It is remarkable that plasmin bound to fibrin is not inhibited by alpha 2-macroglobulin independently of the presence of heparin. On the basis of the reported kinetic data a lifespan of 420 s for plasmin, 66 s for miniplasmin and 4 s for PMN-elastase was calculated, when the enzymes are bound to fibrin in the presence of the four protease inhibitors at physiological plasma concentration. If heparin is present (300 nM) these values decrease to 240 s for plasmin and 42 s for miniplasmin, whereas that of PMN-elastase is unchanged. Thus, the present in vitro kinetic model suggests an antifibrinolytic effect of heparin in a plasma milieu.
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PMID:Heparin modulation of the fibrinolytic activity of plasmin, miniplasmin and neutrophil leukocyte elastase in the presence of plasma protease inhibitors. 753 86


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