scholarly journals The role of endothelium in factor Xa regulation: the effect of plasma proteinase inhibitors and hirudin

Blood ◽  
1988 ◽  
Vol 71 (5) ◽  
pp. 1321-1328
Author(s):  
RC Friedberg ◽  
PO Hagen ◽  
SV Pizzo
Keyword(s):  
Active Site ◽  
Proteinase Inhibitor ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Proteinase Inhibitors ◽  
Factor Xa ◽  
Proteolytic Degradation ◽  
Chromogenic Substrates ◽  
And Function

The role of endothelium in the inhibition of human factor Xa was studied in a plasma environment. Human factor Xa can bind to and function on bovine aortic endothelium in a manner similar to that of bovine factor Xa. Approximately 70% of the bound factor Xa is subject to inhibition by plasma proteinase inhibitors, and the remaining 30% is irreversibly bound as part of a 125 Kd membrane-associated complex not subject to proteolytic degradation. The proportion reversibly bound and its rate of release do not alter with changes in calcium, citrate, heparin, or active proteinase inhibitor concentrations. The principal plasma proteinase inhibitor of human factor Xa was antithrombin III, which accounted for 60% to 65% of factor Xa released from endothelium, with alpha 1-proteinase inhibitor inactivating 20% to 25% and alpha 2- macroglobulin approximately 15%. All of the reversibly bound factor Xa was identified in complex with one of these three proteinase inhibitors. The thrombin active-site inhibitor hirudin was found to markedly accelerate the displacement of reversibly bound factor Xa from the endothelium and to associate specifically with factor Xa without a loss of activity toward chromogenic substrates, perhaps accounting for a novel mechanism of anticoagulation.

scholarly journals The role of endothelium in factor Xa regulation: the effect of plasma proteinase inhibitors and hirudin

Blood ◽  
1988 ◽  
Vol 71 (5) ◽  
pp. 1321-1328 ◽  
Author(s):  
RC Friedberg ◽  
PO Hagen ◽  
SV Pizzo
Keyword(s):  
Active Site ◽  
Proteinase Inhibitor ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Proteinase Inhibitors ◽  
Factor Xa ◽  
Proteolytic Degradation ◽  
Chromogenic Substrates ◽  
And Function

Abstract The role of endothelium in the inhibition of human factor Xa was studied in a plasma environment. Human factor Xa can bind to and function on bovine aortic endothelium in a manner similar to that of bovine factor Xa. Approximately 70% of the bound factor Xa is subject to inhibition by plasma proteinase inhibitors, and the remaining 30% is irreversibly bound as part of a 125 Kd membrane-associated complex not subject to proteolytic degradation. The proportion reversibly bound and its rate of release do not alter with changes in calcium, citrate, heparin, or active proteinase inhibitor concentrations. The principal plasma proteinase inhibitor of human factor Xa was antithrombin III, which accounted for 60% to 65% of factor Xa released from endothelium, with alpha 1-proteinase inhibitor inactivating 20% to 25% and alpha 2- macroglobulin approximately 15%. All of the reversibly bound factor Xa was identified in complex with one of these three proteinase inhibitors. The thrombin active-site inhibitor hirudin was found to markedly accelerate the displacement of reversibly bound factor Xa from the endothelium and to associate specifically with factor Xa without a loss of activity toward chromogenic substrates, perhaps accounting for a novel mechanism of anticoagulation.

Characterization of an Abnormal Antithrombin (Milano 2) with Defective Thrombin Binding

1986 ◽  
Vol 56 (03) ◽  
pp. 349-352 ◽  
Author(s):  
A Tripodi ◽  
A Krachmalnicoff ◽  
P M Mannucci
Keyword(s):  
Venous Thromboembolism ◽  
Active Site ◽  
Inhibitory Activity ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Molecular Defect ◽  
Affinity Adsorption ◽  
Italian Family ◽  
Crossed Immunoelectrophoresis

SummaryFour members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and halfnormal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus’ plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus’ plasma to human α-thrombin immobilized on sepharose beads revealed defective binding of the anti thrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

Characterization of anEscherichia coliSulfite Oxidase Homologue Reveals the Role of a Conserved Active Site Cysteine in Assembly and Function†

Biochemistry ◽  
2005 ◽  
Vol 44 (30) ◽  
pp. 10339-10348 ◽  
Author(s):  
Stephen J. Brokx ◽  
Richard A. Rothery ◽  
Guijin Zhang ◽  
Derek P. Ng ◽  
Joel H. Weiner
Keyword(s):  
Active Site ◽  
Active Site Cysteine ◽  
And Function

Isolation and Partial Characterization of a Novel Circulating Antithrombin

1979 ◽  
Author(s):  
Harry Messmore ◽  
Zaheer Pervez ◽  
Jawed Fareed
Keyword(s):  
Protease Inhibitor ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Serine Protease Inhibitor ◽  
Chromogenic Substrates ◽  
Inhibitor Activity ◽  
Antithrombin Activity ◽  
Life Threatening ◽  
Hydrolysis Of

We have previously reported on a novel circulating anticoagulant (Clin. Res. 22:396 A, 1974. Thromb. and Haem. 38:77, 1977 (abstr) in a 42 year old female who has had repeated episodes of life threatening hemorrhage since the age of 3. Our preliminary studies showed it to be a protein with some of the properties of a heparin activated antithrombin III. This report is on additional studies to further characterize the Inhibitor«The patient’s plasma was fractionated on Sephadex G-200, and the fraction showing immediate acting antithrombin activity was further purified on heparin-sepharose and conconavalin A-sepharose affinity columns. The patient’s inhibitor did not bind to heparin sepharose, and was thus separable from her antithrombin III. It did bind to conconavalin A, and was eluted from the conconavalin A with α - D (+) methylglucoside. It has very broad serine protease inhibitor activity, blocking the hydrolysis of synthetic chromogenic substrates by thrombin, factor Xa, plasmin and trypsin. It did not inhibit Reptilase.Immunochemical assays show it to be α1 antitrypsin. Isoelectric focusing shows it to he a variant of normal, with its isoelectric point being different from a normal control, and pure α1 antitrypsin (commercial, human).The total α1 antitrypsin level in this patient is about 50% of normal, and It has potent immediate acting antithrombin activity. It appears to be similar to a phenotype previously reported as Antithrombin Pittsburgh (Blood 51: 129, 1978).

Role of the Heme Active Site and Protein Environment in Structure, Spectra, and Function of the Cytochrome P450s

2000 ◽  
Vol 100 (2) ◽  
pp. 407-420 ◽  
Author(s):  
Gilda H. Loew ◽  
Danni L. Harris
Keyword(s):  
Active Site ◽  
Cytochrome P450s ◽  
And Function ◽  
Protein Environment

RAT HEPAT0CYTES IN CULTURE INACTIVATE FACTOR Xa.

1987 ◽  
Author(s):  
G D Qureshi ◽  
M Sun ◽  
C Gervin ◽  
H Evans
Keyword(s):  
Serine Proteases ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Rat Hepatocytes ◽  
Factor X ◽  
Clotting Factors ◽  
Hepatocyte Cultures ◽  
The Stability ◽  
Stabilization Period

Plasma contains zymogens of clotting factors, which under various stimuli are activated to serine proteases. Whereas much knowledge has been gained about the activation of clotting factors, relatively little is known about inactivation of these proteases. Antithrombin III has been shown to inactivate some activated clotting factors in plasma. Studies in intact animals have suggested that activated clotting factors are mainly inactivated in the liver. To investigate more fully the role of liver in inactivating the activated factors, we studied the stability of activated factor X(Xa) in hepatocyte cultures. Monolayer cultures on non-proliferating rat hepatocytes were prepared according to the method of Bissell et al. The culture medium was chemically defined and was free from serum or serum products. After the 24 h stabilization period, 0.5 units/ml of 100% activated bovine factor Xa was co-cultured with hepatocytes for 8 h. Samples were collected at 0, ½, 1 2, 4 and 8 h and tested for Xa activity using chromogenic substrate S-2222. At the end of 8 h only 41.07% of the initial Xa activity remained. Xa inactivation was not affected by a commercially prepared unfractionated heparin (1 unit/ml) and estradiol at 12.5, 25, 125 nM, a potentiator and inhibitor of antithrombin III, respectively. Inactivation of Xa in hepatocyte cultures was inhibited by the addition of cycloheximide (10-4M). Our data suggests that factor Xa is inactivated in hepatocyte cultures by one or more hepatic derived factors which do not meet the functional characteristics of antithrombin III.

Antithrombin III and Venous Thrombosis

1979 ◽  
Author(s):  
Duncan P. Thomas
Keyword(s):  
Venous Thrombosis ◽  
Antithrombin Iii ◽  
Physiological Role ◽  
Factor Xa ◽  
Original Description ◽  
Clear Cut ◽  
Naturally Occurring ◽  
At Iii ◽  
General Studies

Increasing interest in the physiological role of inhibitors of coagulation has highlighting the role of antithrombin III (AT III) as the most important naturally occurring inhibitor of venous thrombosis. Since Egeberg’s original description in 1965, it has been recognized that inherited deficiency of AT III is associated with an increased incidence of venous thromboembolism. The role of acquired deficiency of AT III in the pathogenesis of thromboembolism remainsless clear-cut, partly due to methodological differences. While low values have been reported in groups of patients with thromboembolism, estimations of AT III in individual patients are not allways abnormal. In general, studies which have measured protein concentration rather than functional activity, or cl otting assays which measure total antithrombin activity and not specific anti-Factor Xa activity have failed to demonstrate a clear relationship between AT III and thromboembolism. However, in two groups of patients, namely women on oral contraceptives and patients undergoing total hipreplacement, an acquired deficiency of AT III, particularly when measured by anti-Xa clotting assays, correlates highly with postoperative venous thrombosis. Although venous thrombosis may develop in patients despite normal AT III values, an activity below approximately 80% in an anti-Xa clotting assay has been found to be of predictive value in patients subjected to the stress of trauma or surgery.

The effect of phosphatidylserine on the inhibition of human factor Xa by the plasma proteinase inhibitors

1988 ◽  
Vol 50 (6) ◽  
pp. 901-906
Author(s):  
Richard C. Friedberg ◽  
Salvatore V. Pizzo
Keyword(s):  
Human Factor ◽  
Proteinase Inhibitors ◽  
Factor Xa

ChemInform Abstract: Role of the Heme Active Site and Protein Environment in Structure, Spectra, and Function of the Cytochrome P450s

ChemInform ◽  
2010 ◽  
Vol 31 (16) ◽  
pp. no-no
Author(s):  
Gilda H. Loew ◽  
Danni L. Harris
Keyword(s):  
Active Site ◽  
Cytochrome P450s ◽  
And Function ◽  
Protein Environment
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