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At least 19 recordsLinked to original sources
PubMed1979

The contribution of bovine Factor V and Factor Va to the activity of prothrombinase.

The rates of prothrombin activation under initial conditions of invariant concentrations of prothrombin and Factor Xa were studied in the presence of various combinations of Ca2+, homogeneous bovine Factor V, Factor Va, phosphatidylcholine-phosphatidylserine vesicles, and activated bovine platelets. Reactions were monitored continuously through the enhanced fluorescence accompanying the interaction of newly formed thrombin with dansylarginine-N-(3-ethyl-1,5-pentanediyl) amide. The complete prothrombinase (Factor Xa, Ca2+, phospholipid, and Factor Va) behaved as a "typical" enzyme and catalyzed the activation of prothrombin with an apparent Vmax of 2100 mol of thrombin/min/mol of Factor Va or Factor Xa, whichever was the rate-limiting component. Regardless of whether the enzymatic complex was composed of Factor Xa, Ca2+, and plasma Factor Va plus phospholipid vesicles, or activated platelets in the place of the latter components, similar specific activity values were observed. The combination of Factor Va, Ca2+, and phospholipid enhanced the rate of the Factor Xa-catalyzed activation of prothrombin by a factor of 278,000. Factor Va itself when added to Factor Xa, Ca2+, and phospholipid, enhanced the rate of prothrombin activation by a factor of 13,000. Unactivated Factor V appears to possess 0.27% of the procoagulant activity of thrombin-activated Factor Va. From the kinetics of prothrombinase activity, an interaction between Factor Xa and both Factor V and Factor Va was observed, with apparent 1:1 stoichiometries and dissociation constants of 7.3 x 10(-10) M for Factor Va and 2.7 x 10(-9) M for Factor V. The present data, combined with data on the equilibrium binding of prothrombinase components to phospholipid, indicate that the model prothrombinase described in this paper consists of a phospholipid-bound, stoichiometric complex of Factor Va and Factor Xa, with bound Factor Va serving as the "binding site" for Factor Xa, in concert with its proposed role in platelets.

Animals↗
PubMed1979

Phospholipid-binding properties of bovine factor V and factor Va.

Factor V and factor Va binding to single bilayer phospholipid vesicles was investigated by light-scattering intensity measurements. This technique allows the measurement of free and phospholipid-bound protein concentrations from which equilibrium constants can be obtained. As controls, the Ca2+-dependent phospholipid binding of prothrombin and factor X were also studied. The average values obtained for the dissociation constants (Kd) and lipid to protein ratio at saturation, moles/mole (n), for prothrombin (Kd = 2.3 X 10(-6) M, n = 104) and factor X (Kd = 2.5 X 10(-6) M, n = 46) binding to vesicles containing 25% Folch fraction III and 75% phosphatidylcholine in the presence of 2 mM Ca2+ were in agreement with those reported in the literature. The average factor V and factor Va values for the dissociation constants and lipid to protein ratio at saturation (moles/mole) were Kd = 7.2 X 10(-8) M and n = 270 for factor V and Kd = 4.4 X 10(-7) M and n = 76 for factor Va. In contrast to prothrombin and factor X, factor V and factor Va demonstrated Ca2+-independent lipid binding. In addition, the number of factor V and factor Va molecules bound per vesicle was found to be dependent both on the phosphatidylserine content of the vesicle and the ionic strength of the buffer.

Animals↗
PubMed1977

Immunological studies in combined factor V and factor VIII deficiency.

Plasma samples from patients with inherited combined factor V and factor VIII deficiency were examined by immunological methods for the presence of factor V and Factor VIII-related antigens. A factor V-related antigen was consistently demonstrated in all plasma samples by inhibitor neutralization assay using a non-precipitating rabbit antibody. Factor VIII-related antigens were detected by inhibitor neutralization using human antibody and by electroimmunoassay using a precipitating rabbit antibody. The amounts of factor V and factor VIII-related antigens present in the patient's samples were similar to those found in normal human plasma. The findings confirm the presence of normal levels of factor VIII-related antigen in the plasma of these patients and suggest that inactive antigenic determinants of procoagulant factor V and procoagulant factor VIII are also present. The results are consistent with the possibility that a common precursor of porcoagulant factor V and factor VIII is defective in these patients.

Antigens↗
PubMed1976

Combined congenital deficiency of factor V and factor VIII. Report of a further case with some considerations on the hetereditary transmission of this disorder.

A patient with combined factor V and factor VIII deficiency is presented. The bleeding manifestations were mild. The main laboratory feature was a prolonged partial thromboplastin time which was corrected by the addition of adsorbed normal plasma but not by the addition of normal serum, hemophilia A plasma or plasma of another patient with combined factor V and factor VIII deficiency. TGT was also clearly abnormal and was corrected by the addition of adsorbed normal plasma but not by the addition of normal serum. Prothrombin consumption was mildly defective. The prothrombin time was slightly prolonged. Facotr VIII was 12% and factor V 55% of normal. Factor-VIII-associated antigen was normal. The father and a sister of the propositus revealed mild factor V deficiency but normal factor VIII activity and antigen. The parents were not consanguineous. A tentative classification of combined deficiency of factors V and VIII in two groups is proposed. The hereditary transmission of the two types of deficiencies is discussed.

Adult↗
PubMed1979

Isolation and partial characterization of human factor V.

Factor V was isolated from human citrate plasma by very mild purification steps. Cryoprecipitation, fractionation with polyethylene glycol 6000, gel filtration of AcA 44 and adsorption of haptoglobin to immobilized hemoglobin were applied successively, resulting in factor V preparations with a specific activity of 14.5 unit/mg. The yield was 28 percent. A molecular weight of 296 000 was determined by gel filtration and the apparent sedimentation constant found by ultracentrifugation in a sucrose gradient was 7.8 S. Parallel experiments with citrate plasma resulted in the same molecular weight and sedimentation constant. Polyacrylamide gel electrophoresis of factor V in the presence or absence of sodium dodecyl sulfate showed a single protein band. Incubation with human thrombin resulted in an 8-fold activation of the purified factor V.

Chemical Precipitation↗
PubMed1978

Insensitivity of factor V and factor Va to diisopropylfluorophosphate and antithrombin III.

Bovine plasma Factor V and Factor Va, the latter prepared by thrombin or venom activator action on Factor V, are not inactivated by diisopropylfluorophosphate or antithrombin III nor do they form identifiable complexes with either of these reagents. On the basis of these data, it is concluded that bovine Factor V and Factor Va are not serine proteases.

Antithrombins↗
PubMed1976

An immunological investigation of factor VIII associated antigen in combined factor V and factor VIII deficiency.

The behavior of factor VIII associated antigen of three patients with combined factor V and factor VIII deficiency has been evaluated in several immunological systems. Factor VIII associated antigen resulted to be normal or higher than normal in all three patients in the radial immunodiffusion and in the electroimmunoassay systems. In the bidimensional electrophoresis system only one factor VIII precipitate was evident and such factor VIII precipitate showed the same electrophoretic mobility as normal factor VIII antigen. These findings firmly establish the fact that the factor VIII defect in congenital combined factor V and factor VIII deficiency is of the hemophilia type.

Antigens↗
PubMed1977

Inherited combined deficiency of factor V and factor VIII: report of a case with normal factor VIII antigen and ristocetin-induced platelet aggregation.

A patient with inherited combined deficiency of factor V and factor VIII is reported, who demonstrated normal levels of factor VIII antigen and plasma cofactor for ristocetin-induced platelet aggregation. The relationship of this condition to classical hemophilia and von Willebrand's disease is discussed. The data presented suggest that multiple loci on at least 2 chromosomes are necessary for the normal expression of factor VIII activity.

Adult↗
PubMed1977

Platelet adhesiveness and aggregation in combined factor V and factor VIII deficiency and in combined factor VII and factor VIII deficiency.

Platelet aggregation and adhesiveness were studied in 3 patients with combined factor V and factor VIII deficiency and in 3 patients with combined factor VII and factor VIII deficiency. The first three patients belonged to three different kindreds whereas the second group belonged to the same kindred. Serotonin C14 uptake and release was also found to be normal in these patients. These studies indicate that platelet function is normal in combined defects of factor VIII. These findings were in agreement with the presence of a normal bleeding time and a normal factor VIII antigen level in all these patients.

Blood Coagulation Disorders↗
PubMed1979

[Case report of congenital deficiency of factor V and factor VIII].

A case of a rare congenital combined deficiency of factor V (14%) and factor VIII (30%) is described for the first time in our literature. Nine years old girl was admitted to hospital because of nightly bleedings from hyperplastic and inflamed gums. Clinical picture was mild what is in accordance with the results of coagulation studies. Under substitution therapy tooth extraction passed without complications.

Child↗
PubMed1979

The subunit structure of thrombin-activated factor V. Isolation of activated factor V, separation of subunits, and reconstitution of biological activity.

Activated Factor V (Va) was prepared by treating a high molecular weight form of Factor V with thrombin. The activated Factor V was isolated by ion exchange chromatography and was composed of two polypeptide chains (Mr = 115,000 and 73,000). These chains were separated by ion exchange chromatography in the presence of EDTA. Biologically active Factor Va was restored from the inactive chains by incubation of the two chains in buffers containing MnCl2. Restoration of biological activity was correlated with formation of a complex between the chains as monitored by either disc gel electrophoresis or gel filtration chromatography. The apparent molecular weight of the activated Factor V was 290,000. Factor V was not dissociated in EDTA. However, this protein was split by thrombin to yield an activation intermediate composed of two chains (Mr = 210,000 and 115,000). Like activated Factor V, the two chains of the intermediate can be dissociated in EDTA and separated by gel filtration chromatography. The Factor V activity was restored by incubation of the two inactive chains in buffers containing MnCl2. Like Factor Va, restoration of the biological activity corresponds to formation of a complex between the chains with a higher molcular weight than either of the isolated chains. Incubation of the activation intermediate with thrombin increased the specific activity 3- to 4-fold. This increase in specific activity resulted from cleavage of the heavy chain of the Factor V intermediate by thrombin.

Animals↗
PubMed1977

Factor V activity of platelets: evidence for an activated factor V molecule and for a platelet activator.

This study was prompted by the observation that fresh platelet suspensions--prepared by gel filtration or albumin density gradient centrifugation--possessed only minimal factor V activity, whereas frozen-and-thawed platelet suspensions possessed striking factor V activity. Results of experiments with fresh suspensions suggested that unaltered platelets did not bind plasma factor V. The factor V activity of frozen-and-thawed platelet suspensions was markedly diminished after exposure to a factor V antibody, was not activated by thrombin, and was not associated with an increase in factor V antigen over that found in fresh platelet suspensions. Consequently, disruption by freezing and thawing must have resulted in the appearance of small amounts of an activated factor V molecule in platelet suspensions. Disrupted platelets were shown to activate native factor V, but an interaction between a platelet activator and traces of native factor V in fresh suspensions could not be demonstrated to account for the full activity of frozen-and-thawed suspensions. Apparently, therefore, platelets also contained an activated factor V molecule. Adding collagen, but not adenosine 5'-diphosphate to fresh platelet suspensions increased their factor V activity. Release of an activated platelet factor V molecule after exposure to collagen could represent a physiologically significant early step in hemostasis.

Antibodies↗
PubMed2025

Venous thromboembolism laboratory testing (factor V Leiden and factor II c.∗97G>A), 2025 revision: A technical standard of the American College of Medical Genetics and Genomics (ACMG).

Venous thromboembolism (VTE) occurs when a blood clot forms in a vein. The etiology of VTE is multifactorial, including both environmental and genetic factors. Among the genetic factors, factor V Leiden and factor II c.∗97G>A (formerly referred to as prothrombin 20210G>A) are the 2 most common genetic variants associated with VTE. Testing for these variants is one of the most common referrals in clinical genetics laboratories. Although the methodologies for testing these 2 variants are relatively straightforward, the clinical implementation can be complicated regarding test indications, risk assessment for occurrence, and recurrence of VTE and related genetic counseling. This document provides an overview of VTE, information about the variants and their influence on risk, considerations before initiating genetic testing, and the clinical and analytical sensitivity and specificity of the tests. Key information that should be included in the laboratory report is also provided. This document supersedes the Technical Standards and Guidelines for Venous Thromboembolism Laboratory Testing originally published in 2005 and revised in 2018. It is designed for genetic testing professionals familiar with the disease and the analysis methods.

Humans↗
PubMed1978

Patients with congenital factor V deficiency have decreased factor Xa binding sites on their platelets.

Human platelets have binding sites for plasma coagulation Factor X(a) that are available only after the platelet release reaction. Platelets from 15 normal donors bound 216+/-52 (SD) molecules of Factor X(a) per platelet. The association of Factor X(a) with its platelet surface receptor results in a 300,000-fold increase in the catalytic activity of Factor X(a) in forming thrombin from prothrombin. The turnover number for platelet-bound Factor X(a) was 1,850+/-460 mol thrombin/ml per min per mol Factor X(a) in experiments with platelets from 15 normal donors. Platelets from five patients with varying degrees of Factor V deficiency were investigated to determine whether or not coagulation Factor V participates in either aspect of the Factor X(a)-platelet interaction. The binding of Factor X(a) to platelets and the accompanying increase in rate of thrombin formation were either reduced in parallel or absent in each case with values ranging from 0 to 45% of control values. The apparent affinity of Factor X(a) from Factor V-deficient patients was normal when platelet binding was detected. The supernate from thrombin-treated control platelets, which contains Factor V activity, corrected the Factor X(a) binding deficiency of the platelets from three patients tested. Immunoreactive Factor V determined with an homologous antibody corresponded to the functional Factor V activity of platelets from one patient with Factor V deficiency, suggesting that the patient's platelets have a decreased amount of normal Factor V. The ability of platelets from the patients to bind Factor X(a) and increase the rate of thrombin formation correlated with the severity of each patient's bleeding disorder better than the plasma level of Factor V. The results indicate that Factor V is required for the Factor X(a)-platelet interaction and that thrombin formation at the platelet surface is important in normal hemostasis.

Adult↗
PubMed1975

Immunochemical studies on factor V.

Native bovine factor V exhibits a molecular weight of 300000 as determined by gel filtration of untreated plasma. Highly purified factor V exhibits multiple molecular weight forms which range from small active fragments to aggregates of several million which are generated during the purification on cellulose phosphate. Isoelectric focusing on a single high-molecular-weight species produced a single protein and activity peak at pH 4.65. Factor V activity is associated with each protein band observed following polyacrylamide gel electrophoresis. Antisera to factor V prepared in rabbits produces a time-dependent and concentration-dependent inhibition of factor V activity in plasma and purified factor V. The multiple molecular weight forms of factor V appear equivalent upon immunodiffusion and on immunoelectrophoresis migrate as an alpha globulin between albumin and fibrinogen. Immunoprecipitation arcs are equivalent in plasma and serum. Factor V consists of two major types of subunits, a light chain (73000), aggregates of which form the high-molecular-weight species, and a heavy chain (125 000). Using preparations containing one or both chains isolated by disc gel electrophoresis, antiserum was shown to contain two families of antibodies, one against each subunit. Cross reactivity with both light and heavy chain antigens is observed in sheep and goat but not monkey or human plasma. The antisera also neutralized goat and sheep factor V activity.

Animals↗
PubMed1979

Isolation and characterization of single chain bovine factor V.

A procedure for the isolation of bovine Factor V has been developed. The Factor V is isolated from bovine plasma by a series of steps including barium citrate adsorption, polyethylene glycol precipitation, QAE-cellulose adsorption, hydrophobic chromatography on octyl Sepharose, ammonium sulfate fractionation, preparative electrophoresis on acrylamide gels, and finally, phenyl Sepharose chromatography. During isolation, judicious use of inhibitors including benzamidine hydrochloride, soybean trypsin inhibitor, and diisopropylphosphorofluoridate has been applied to prevent activation of the Factor V TO Factor Va. The activity of the isolated protein increases by a factor of 80 when stimulated by catalytic amounts of thrombin. The specific activity of the material after thrombin activation is 1250 units/mg of protein when evaluated versus a bovine Factor V standard in human factor V-deficient plasma. The isolated protein is a single component when analyzed by a variety of electrophoretic techniques and has been characterized in terms of its gross physical and chemical properties. Bovine Factor V is a single chain glycoprotein which has a molecular weight of 330,000. The single chain nature of the molecule has been established by sedimentation equilibrium studies of the native molecule and on the molecule in 6 M guanidinium chloride with and without disulfide bond reduction. In addition to these mass measurements, the single chain nature of the molecule has been established by hydrodynamic estimation of the random coil volume by sedimentation velocity studies of the reduced carboxyamidomethylated protein in 6 M guanidinium chloride. Native Factor V has a sedimentation coefficient so20,w of 9.19 S, which indicates the molecule is highly asymmetric. The frictional ratio f/fmin for the molecule is estimated to be 2.01, and the axial ratio of the equivalent prolate ellipsoid is 25:1. Thus, present data suggest that Factor V is a rod-like molecule composed of a single chain.

Amino Acids↗