AUTOACTIVATION OF HUMAN PLASMA PREKALLIKREIN

1987 ◽  
Author(s):  
G Tans ◽  
J Rosing ◽  
M Berrettini ◽  
B Lammle ◽  
J H Griffin
Keyword(s):  
Ionic Strength ◽  
Human Plasma ◽  
Rate Constant ◽  
Trypsin Inhibitor ◽  
Active Form ◽  
Second Order ◽  
Reversible Inhibitor ◽  
Lag Phase ◽  
Contact Activation ◽  
Amidolytic Activity

Incubation of purified human plasma prekallikrein with sulfatides or dextran sulfate resulted in spontaneous activation of prekallikrein as judged by the appearance of amidolytic activity towards the chromogenic substrate H-D-pro-phe-arg-p-nitroanilide (S 2302). The time course of generation of amidolytic activity was sigmoidal with an apparent lag phase followed by a rapid activation until finally a plateau was reached. Soybean trypsin inhibitor completely blocked prekallikrein activation whereas corn, limabean and ovomucoid trypsin inhibitor did not. The Ki of the reversible inhibitor, benzamidine, for autoactivation (240 uM) was identical to the Ki of benzamidine for kallikrein. Thus, spontaneous prekallikrein activation and kallikrein showed the same specificity for a number of serine protease inhibitors, indicating that prekallikrein is activated by its own enzymatically active form, kallikrein. Immunoblotting analysis showed that, concomitant with the appearance of amidolytic activity, prekallikrein was cleaved. However, prekallikrein was not quantitatively converted into two-chain kallikrein since other polypeptide products were visible on the gels. This accounts for the observation that in amidolytic assays not all prekallikrein present in the reaction mixture was measured as active kallikrein. Kinetic analysis showed that prekallikrein activation can be described by a second-order reaction mechanism in which prekallikrein is activated kallikrein. The apparent second order rate constant was 27000 M-ls-1 (pH 7.2, 50 uM sulfatides, ionic strength 1=0.06, at 37°C). Autocatalytic prekallikrein activation was strongly dependent on the ionic strength, since there was a considerable decrease in the rate of the reaction at high salt concentrations. Our data support a prekallikrein autoactivation mechanism in which surface-bound kallikrein activates surface-bound prekallikrein. The rate constant of autoactivation is considerably lower than the rate constants reported for Factor Xlla dependent prekallikrein formation. Autocatalytic prekallikrein activation may, however, contribute to kallikrein formation during the initiating phase of contact activation.

scholarly journals Nonplasminogen-dependent protease in human plasma

Blood ◽  
1979 ◽  
Vol 54 (3) ◽  
pp. 607-613
Author(s):  
JA Marcum ◽  
DL Kline
Keyword(s):  
Ionic Strength ◽  
Human Plasma ◽  
Trypsin Inhibitor ◽  
Fibrinolytic Activity ◽  
Coagulation Factors ◽  
Contact Activation ◽  
Ph Optimum ◽  
Salt Addition ◽  
Caseinolytic Activity ◽  
Pancreatic Trypsin Inhibitor

Abstract Equal volumes of plasma and 0.3 M K2HPO4, pH 7.4, were mixed, diluted 20-fold, and adjusted to pH 5.2. After incubation at 37 degrees C for 30 min, the euglobulin percipitate, redissolved in 0.1 M K2HPO4, pH 7.4, developed caseinolytic activity (0.05 CTA U/ml). Na2HPO4 or NaCl of similar ionic strength could replace K2HPO4. The pH optimum of the protease was 6.5, activity falling off sharply below pH 6.0 and above 7.4. The proteolytic activity was inhibited by diisopropylphosphofluoridate and by pancreatic trypsin inhibitor, but was not inhibited by soybean trypsin inhibitor. The activity was not due to plasmin, contact activation, or coagulation factors, since it was fully generated in plasminogen-depleted, factors XII, XI, VII deficient, and prekallikrein-deficient plasmas. Purified Cl-esterase was not caseinolytic in our system. Redissolved euglobulin precipitate prepared from normal plasma without salt addition could serve as starting material for the generation of caseinolytic activity, as could serum, indicating that the Hageman factor cofactor and thrombin are not required. The protease had no detectable procoagulant or fibrinolytic activity.

scholarly journals Nonplasminogen-dependent protease in human plasma

Blood ◽  
1979 ◽  
Vol 54 (3) ◽  
pp. 607-613
Author(s):  
JA Marcum ◽  
DL Kline
Keyword(s):  
Ionic Strength ◽  
Human Plasma ◽  
Trypsin Inhibitor ◽  
Fibrinolytic Activity ◽  
Coagulation Factors ◽  
Contact Activation ◽  
Ph Optimum ◽  
Salt Addition ◽  
Caseinolytic Activity ◽  
Pancreatic Trypsin Inhibitor

Equal volumes of plasma and 0.3 M K2HPO4, pH 7.4, were mixed, diluted 20-fold, and adjusted to pH 5.2. After incubation at 37 degrees C for 30 min, the euglobulin percipitate, redissolved in 0.1 M K2HPO4, pH 7.4, developed caseinolytic activity (0.05 CTA U/ml). Na2HPO4 or NaCl of similar ionic strength could replace K2HPO4. The pH optimum of the protease was 6.5, activity falling off sharply below pH 6.0 and above 7.4. The proteolytic activity was inhibited by diisopropylphosphofluoridate and by pancreatic trypsin inhibitor, but was not inhibited by soybean trypsin inhibitor. The activity was not due to plasmin, contact activation, or coagulation factors, since it was fully generated in plasminogen-depleted, factors XII, XI, VII deficient, and prekallikrein-deficient plasmas. Purified Cl-esterase was not caseinolytic in our system. Redissolved euglobulin precipitate prepared from normal plasma without salt addition could serve as starting material for the generation of caseinolytic activity, as could serum, indicating that the Hageman factor cofactor and thrombin are not required. The protease had no detectable procoagulant or fibrinolytic activity.

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

On the Interaction Between Human Plasma Kallikrein and C1-Esterase Inhibitor

1983 ◽  
Vol 49 (03) ◽  
pp. 193-195 ◽  
Author(s):  
Torbjörn Nilsson
Keyword(s):  
Dissociation Constant ◽  
Human Plasma ◽  
Rate Constant ◽  
Enzyme Inhibitor ◽  
Order Rate Constant ◽  
Second Order ◽  
Plasma Kallikrein ◽  
First Order ◽  
Order Rate ◽  
Esterase Inhibitor

SummaryThe kinetics of the reaction between human plasma kallikrein and CĪ-esterase inhibitor was studied in a purified system. By monitoring the inhibition reaction for extended periods of time, it was found to proceed in two consecutive steps, a fast reversible second-order binding step followed by a slower, irreversible first-order transition. The rate constants in this reaction model were determined, as well as the dissociation constant of the initial, reversible enzyme-inhibitor complex. Thus, at 37° C the second-order rate constant was found to be 5 · 104 M -1 · s-1, the first order rate constant was 5 · 10-4 s-1 and the dissociation constant K was 1.5 · 10-8 M. Heparin (28 U/ml) and 6-aminohexanoic acid (10 mM) had no effect on the k1 of the of the reaction.

Base decomposition of dichromate

1977 ◽  
Vol 30 (1) ◽  
pp. 211 ◽  
Author(s):  
BW Clare ◽  
DM Druskovich ◽  
DL Kepert ◽  
JH Kyle
Keyword(s):  
Sodium Chloride ◽  
Ionic Strength ◽  
Rate Constant ◽  
Calcium Ion ◽  
Order Rate Constant ◽  
Second Order ◽  
Tetraalkylammonium Ions ◽  
Order Rate ◽  
Tetramethylammonium Chloride ◽  
Total Ionic Strength

The rate of decomposition of dichromate, Cr2O72-, to form chromate, CrO42-, is very dependent upon the choice of cation, and its concentration. At a total ionic strength of 1.0 mol l-1 and at 25.0°C, the second-order rate constant decreases in the order Ca2+ (2600 mol-1 l. s-1) >> K+ + (960) > Na+ (920) >Li+ (700)>> bistet2+ (410) >> Me4N+ (125) >> Et4N+ (35) where bistet2+ is the N,N,N,N',N',N'-hexamethylethylene-1,2-diammonium ion. In the presence of sodium chloride the second-order rate constant increases as the ionic strength increases (200 and 1900 mol-1 l. s-1 at ionic strengths of 0 and 2.7 mol l-1 respectively), whereas in tetramethylammonium chloride a maximum is reached at intermediate ionic strengths. The equilibrium between dichromate and hydrogen chromate is shifted towards the dichromate side in the presence of tetraalkylammonium ions, and towards the hydrogen chromate side in the presence of calcium ion.

THE KINETICS OF THE CHELATION OF NICKEL (II) AND 1,10-PHENANTHROLINE

1964 ◽  
Vol 42 (4) ◽  
pp. 934-940 ◽  
Author(s):  
P. F. Barrett ◽  
W. MacF. Smith
Keyword(s):  
Ionic Strength ◽  
Rate Constant ◽  
Order Rate Constant ◽  
Second Order ◽  
Hydrogen Ion ◽  
Kinetic Behavior ◽  
Ion Concentrations ◽  
Order Rate ◽  
Kinetics Of ◽  
Limiting Values

The kinetics of the formation of the bidentate monocomplex of 1,10-phenanthroline and nickel (II) have been examined spectrophotometrically at ionic strength 0.5 over the range of temperatures 8 to 37 °C and over the range of hydrogen ion concentrations 0.01 to 0.30 molar. The kinetic behavior over the range of conditions is consistent with that found at 25 °C by Margerum, Bystroff, and Banks. The limiting values for the second-order rate constant for the reaction at high acidities have been assessed and imply associated values of ΔH≠and ΔS≠ of 9.5 kcal mol−1 and −5.3 e.u. respectively.

Inhibition of Coagulation and Fibrinolysis by Aromatic Amidino Compounds

1971 ◽  
Vol 25 (03) ◽  
pp. 391-404 ◽  
Author(s):  
J.D Geratz
Keyword(s):  
Prothrombin Time ◽  
Human Plasma ◽  
Partial Thromboplastin Time ◽  
Inhibitory Effect ◽  
Clot Lysis ◽  
Similar Degree ◽  
Contact Activation ◽  
Plasma Clot ◽  
Human Thrombin ◽  
Canine Plasma

Summary1. Aromatic diamidines which are potent inhibitors of trypsin possess a marked inhibitory effect on the clotting activity of human thrombin and on the prothrombin time and partial thromboplastin time of human plasma. They also block the contact activation phase of the coagulation process. The strongest inhibitor among the compounds tested was M & B 4596 which was followed in second place by pentamidine.2. Pentamidine was 10 times more active than ε-ACA in impeding streptokinase-induced lysis of human plasma clots. It was 100-200 times stronger than ε-ACA in inhibiting the activation of bovine plasminogen by activators formed from the interaction between streptokinase and either human plasmin(ogen) or human plasma.3. The prothrombin time and partial thromboplastin time of canine plasma were less susceptible to inhibition by pentamidine than the same tests on human plasma. Clot lysis in the canine system was inhibited by pentamidine to a similar degree as in the human system. After intravenous injection of pentamidine in the dog there occurred the expected prolongation of the partial thromboplastin time and of the clot lysis time.

Determination of rate constants of redox reactions of second order from current-less potential-time curves by a simplified graphical-numerical method

1983 ◽  
Vol 48 (5) ◽  
pp. 1358-1367 ◽  
Author(s):  
Antonín Tockstein ◽  
František Skopal
Keyword(s):  
Numerical Method ◽  
Explicit Form ◽  
Rate Constant ◽  
Optimization Algorithm ◽  
Rate Constants ◽  
Redox Reactions ◽  
Second Order ◽  
Wide Region ◽  
Recurrent Formula

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

scholarly journals Kinetics and Mechanistic Study of Hydrolysis of Adenosine Monophosphate Disodium Salt (AMPNa2) in Acidic and Alkaline Media

2019 ◽  
Vol 17 (1) ◽  
pp. 544-556
Author(s):  
Yoke-Leng Sim ◽  
Beljit Kaur
Keyword(s):  
Rate Constant ◽  
Adenosine Monophosphate ◽  
Disodium Salt ◽  
Second Order ◽  
Information Storage ◽  
Alkaline Media ◽  
Basic Medium ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Hydrolysis Of

AbstractPhosphate ester hydrolysis is essential in signal transduction, energy storage and production, information storage and DNA repair. In this investigation, hydrolysis of adenosine monophosphate disodium salt (AMPNa2) was carried out in acidic, neutral and alkaline conditions of pH ranging between 0.30-12.71 at 60°C. The reaction was monitored spectrophotometrically. The rate ranged between (1.20 ± 0.10) × 10-7 s-1 to (4.44 ± 0.05) × 10-6 s-1 at [NaOH] from 0.0008 M to 1.00M recorded a second-order base-catalyzed rate constant, kOH as 4.32 × 10-6 M-1 s-1. In acidic conditions, the rate ranged between (1.32 ± 0.06) × 10-7 s-1 to (1.67 ± 0.10) × 10-6 s-1 at [HCl] from 0.01 M to 1.00 M. Second-order acid-catalyzed rate constant, kH obtained was 1.62 × 10-6 M-1 s-1. Rate of reaction for neutral region, k0 was obtained from graphical method to be 10-7 s-1. Mechanisms were proposed to involve P-O bond cleavage in basic medium while competition between P-O bond and N-glycosidic cleavage was observed in acidic medium. In conclusion, this study has provided comprehensive information on the kinetic parameters and mechanism of cleavage of AMPNa2 which mimicked natural AMP cleavage and the action of enzymes that facilitate its cleavage.

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