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Examining thrombin hydrolysis of the factor XIII activation peptide segment leads to a proposal for explaining the cardioprotective effects observed with the factor XIII V34L mutation.

In the blood coagulation cascade, thrombin cleaves fibrinopeptides A and B from fibrinogen revealing sites for fibrin polymerization that lead to insoluble clot formation. Factor XIII stabilizes this clot by catalyzing the formation of intermolecular cross-links in the fibrin network. Thrombin activates the Factor XIII a(2) dimer by cleaving the Factor XIII activation peptide segment at the Arg(37)-Gly(38) peptide bond. Using a high performance liquid chromatography assay, the kinetic constants K(m), k(cat), and k(cat)/K(m) were determined for thrombin hydrolysis of fibrinogen Aalpha-(7-20), Factor XIII activation peptide-(28-41), and Factor XIII activation peptide-(28-41) with a Val(34) to Leu substitution. This Val to Leu mutation has been correlated with protection from myocardial infarction. In the absence of fibrin, the Factor XIII activation peptide-(28-41) exhibits a 10-fold lower k(cat)/K(m) value than fibrinogen Aalpha-(7-20). With the Factor XIII V34L mutation, decreases in K(m) and increases in k(cat) produce a 6-fold increase in k(cat)/K(m) relative to the wild-type Factor XIII sequence. A review of the x-ray crystal structures of known substrates and inhibitors of thrombin leads to a hypothesis that the new Leu generates a peptide with more extensive interactions with the surface of thrombin. As a result, the Factor XIII V34L is proposed to be susceptible to wasteful conversion of zymogen to activated enzyme. Premature depletion may provide cardioprotective effects.

Animals↗

The combined effect of fibrin formation and factor XIII A subunit Val34Leu polymorphism on the activation of factor XIII in whole plasma.

The first step in the activation of blood coagulation factor XIII (FXIII) is the proteolytic cleavage of the potentially active A subunit (FXIII-A) by thrombin at Arg37-Gly38. Both fibrin formation and FXIII-A Val34Leu polymorphism influence the rate of proteolytic activation of purified factor XIII, however their relative importance and interaction in determining the time of onset and the rate of FXIII activation in whole plasma have not yet been explored. In the present study it was shown that in plasma, fibrin formation preceded the truncation of FXIII-A by thrombin, the activation process took place exclusively on the surface of newly formed fibrin and activated FXIII remained associated with the fibrin clot. The time of fibrin formation closely correlated with the time of FXIII activation, while there was no significant relationship between the time of FXIII activation and FXIII-A Val34Leu genotype. However, in the case of Leu34 variant the lag phase between fibrin formation and FXIII-A truncation was significantly shorter than in the case of Val34 variant. The results suggest that in whole plasma the onset of FXIII activation is determined by fibrin formation, while the rate of activation is modulated by Val34Leu polymorphism.

Adult↗

Factor XIII ABristol 1: detection of a nonsense mutation (Arg171-->stop codon) in factor XIII A subunit deficiency.

Molecular analysis has been performed on a patient with coagulation factor XIII A subunit deficiency. A previously published genomic sequence indicates that exon 4 of the factor XIII A subunit gene contains two TaqI restriction sites within which arginine (CGA)-->stop (TGA) nonsense mutations are possible. Oligonucleotide primers were therefore used to amplify exon 4 by the polymerase chain reaction. TaqI digestion of the 326 base pair (bp) product derived from normal genomic DNA yielded expected fragments of 244, 73 and 9 bp in size. In the case of the patient, however, an additional fragment of 253 bp was present. Direct sequence analysis showed that the 5' TaqI site had been lost from one allele by a C-->T transition at nucleotide 598. Family studies demonstrated the mutation in the patient's father but no other first-degree relatives. This is the third independent mutation described in the factor XIII A subunit gene and the first to be identified in a patient compound heterozygous for the disorder.

Adult↗

Dynamics of blood coagulation factor XIII in ulcerative colitis and preliminary study of the factor XIII concentrate.

Blood coagulation studies were performed in twenty patients with ulcerative colitis (UC). At the active stage of UC, a marked increase in platelet count and fibrinogen concentration, and a marked decrease in Factor XIII activity level were observed. At the active stage of UC, four patients were treated with Factor XIII concentrate leading to reduction of pain, bleeding and endoscopic findings.

Adult↗

Immunochemical studies of human factor XIII.

Plasma factor XIII circulates as a noncovalently associated, tetrameric zymogen (a2b2). The b subunit may act as a carrier protein for the a subunit, which possesses the potential catalytic function. In order to define interactions that occur between the two subunits, a sensitive and specific RIA for the b subunit has been developed. Purified plasma factor XIII was incubated with thrombin and chromatographed on organomercurial agarose to separate the subunits. Pure b chain eluted in buffer containing CaCl2. This material was used as the standard b preparation, both for preparing a monospecific antiserum and for establishing the assay. The linear range of the assay is 7 to 700 ng/ml (Ca. 0.1 to 10 nM b subunit), with a minimum detectable dose of l. Data were analyzed by use of the logit-log transformation of antigen-binding curves. The dose-response slope for standard b is -2.76 + or - 0.20, with a potency (ED50) of 74.9 + or - 6.5 ng/ml. This RIA is also valid for determining b subunit concentration of plasma and serum. The dose-response slope for the plasma system is -2.69 + or - 0.20 with an ED50 identical to that of the purified system. By this method the mean b subunit concentration in normal human plasma (corrected for anticoagulant) is 13.8 micro g/ml (ca. 0.15 micro M). The concentration in serum is 13.6 micro g/ml, which shows that b subunit is quantitatively recovered after coagulation has occurred.

Animals↗

Prophylaxis in rare coagulation disorders -- factor XIII deficiency.

Factor XIII (FXIII) deficiency is a very rare form of haemophilia resulting in different manifestations of bleeding disorders, but characterised by umbilical stump bleeding in up to 80% of patients. Although originally described as the final enzyme in the clotting cascade, FXIII is now recognised to play a role throughout the clotting process. Treatment with FXIII concentrate (Fibrogammin P, ZLB Behring) results in the re-establishment of a normal clotting pattern. Prophylaxis studies in France and the USA have demonstrated an excellent response following monthly prophylaxis with this plasma-derived, pasteurised concentrate. Patients with FXIII deficiency have good control of bleeding, with no development of inhibitors, or viral seroconversion. The development of registries such as that in the USA will enable the different manifestations of the disease to be explored.

Blood Coagulation Disorders↗

Phenotype-genotype characterization of 10 families with severe a subunit factor XIII deficiency.

Factor XIII (FXIII) deficiency is a very rare severe autosomal bleeding disorder with a frequency of 1:2,000,000 in the general population and only a few patients have been genetically characterized so far. We report a phenotype-genotype characterization of 10 unrelated Iranian patients. Two FXIII (transglutaminase) activity assays showed no FXIII activity, except a conserved residual activity in patients receiving prophylactic substitution treatment. FXIII antigen concentrations measured by two immunoassays were comparable. Genotype characterization identified four novel mutations (2 missense and 2 small deletions) and two previously reported missense mutations in the FXIII A subunit gene (F13A). Molecular modeling was carried out to reveal the structural consequences of the missense mutations, that caused the replacement of an arginine residue involved in the formation of structurally important extensive hydrogen-bonded network. The replacements [c.320G>A (p.Arg77His) in the beta-sandwich, c.868C>T (p.Arg260Cys), c.869G>A (p.Arg260His) and c.1236G>T (p.Arg382Ser) in the core domain] resulted in the loss or impairment of such H-bonded network. Energy decomposition analysis demonstrated that this situation leads to the instability and perhaps to the incorrect folding of the A subunit, that would explain the development of severe FXIII deficiency.

Adult↗

Factor XIII deficiency due to a Leu660Pro mutation in the factor XIII subunit-a gene in three unrelated Palestinian Arab families.

In this report we describe the molecular basis of FXIII a-subunit deficiency in three unrelated Palestinian Arab families. In three patients representing each family two substitutions were identified in exon 14 on both alleles: C to G change resulting in a Gln651Glu substitution (a previously described polymorphism) and a T to C transition causing Leu660Pro substitution. The latter is a new mutation which creates a restriction site for FnuDII enzyme. Restriction analysis performed in members of the three families clearly distinguished between severely affected patients, obligate carriers and unaffected subjects. A population survey failed to detect the mutation among 250 Jewish individuals but did detect two heterozygotes among 300 Arabs suggesting a 0.0033 frequency for the Pro660 allele in this population. In two out of the three families the Pro660 allele was linked to allele 5 of the 5' short tandem repeat polymorphism within the FXIII a-subunit gene suggesting that the mutation might have occurred at least twice. cDNA obtained from mRNA isolated from patients' platelets and monocytes appeared similar in size to that of normal control indicating that the Leu660Pro mutation does not affect mRNA synthesis. Computer modeling based on cristallographic studies of the a-subunit of factor XIII predicted that the mutant protein is expected to misfold into a structure which is either unstable or susceptible to degradation.

Arabs↗

Determinants of substrate specificity for factor XIII.

Plasma factor XIIIa (A*2) is a regulator in balancing the opposing coagulation and fibrinolytic processes. Its enzymatic activity is to catalyze epsilon-(gamma-glutamyl)lysyl bonds between certain substrate molecules to link them by strong bonds. The primary physiological substrates are crosslinks between the gamma and alpha chains of fibrin that produce gamma-gamma-dimer and alpha-polymer, between alpha 2-plasmin inhibitor (alpha 2-PI) and alpha chains of fibrin, and between fibronectin and fibrin. We have characterized a unique factor XIII antibody that is specific for the middle 54-kDa section of A*2. It does not react with the zymogen (A2) or the inactive intermediate (A'2), and it does not inhibit the active center, as do most patient antibodies to factor XIII. This antibody inhibits the formation of A*2-fibrin complexes. Because of this specificity, the antibody was used to study other substrate interactions. It inhibited formation of fibronectin-factor XIIIa complexes, similarly to fibrin, and there was very little crosslinking of fibronectin to a fibrin clot. However, the amount of alpha 2-PI crosslinked to a fibrin clot was normal. It was concluded that this antibody interferes with exosite binding of fibrin and fibronectin interferes with exosite binding of fibrin and fibronectin in a similar way, while at least one critical exosite binding domain for alpha 2-PI is different from those of the other two substrates. Furthermore, with this antibody, it was shown that both alpha 2-PI-alpha chain crosslinking and alpha-polymer formation are necessary to normalize the rate of fibrinolysis.

Amino Acid Sequence↗

A new family with congenital factor XIII deficiency showing a deficit of both subunit A and B. Type I factor XIII deficiency.

In this study we present a new case of Factor XIII deficiency. The proposita, a 34 year old woman, showed a deficiency of both subunit a and subunit b, and a moderate bleeding tendency. Because of the concomitant decrease of subunits a and b the proposita is considered to be an example of Type I disease. Factor XIII levels were less than 10% both as activity and antigen. Several family members showed intermediate levels of both subunit a and b and were asymptomatic. They were considered to be heterozygotes. The hereditary pattern is autosomal incompletely recessive. Type I disease appears much less frequent than Type II.

Adult↗

Simvastatin depresses blood clotting by inhibiting activation of prothrombin, factor V, and factor XIII and by enhancing factor Va inactivation.

BACKGROUND: The mechanism of the antithrombotic action of statins is unclear. The aim of this study was to evaluate the effects of simvastatin on the coagulation process at sites of microvascular injury. METHODS AND RESULTS: Tissue factor-initiated coagulation was assessed in blood samples collected every 30 seconds from bleeding-time wounds of 17 patients who had advanced coronary artery disease and total cholesterol levels of 224.6+/-11.8 mg/dL (mean+/-SEM). Quantitative Western blotting for time courses of fibrinogen depletion and activation of prothrombin, factor V, and factor XIII was performed before and after 3 months of simvastatin treatment (20 mg/d). Simvastatin induced reductions in total cholesterol (23%) and LDL-cholesterol (36%), which were accompanied by significant decreases in the rates of prothrombin activation (16.2+/-2.1%; P=0.004), formation of alpha-thrombin B-chain (27.4+/-1.8%; P=0.001), generation of factor Va heavy chain (29.7+/-3.1%; P=0.007) and factor Va light chain (18.9+/-1.2%; P=0.02), factor XIII activation (19.8+/-1.3%; P=0.001), and fibrinogen conversion to fibrin (72.2+/-3%; P=0.002). Posttreatment fibrinopeptides A and B concentrations, determined by using high-performance liquid chromatography, were reduced within the last 30 seconds of bleeding. The 30-kDa fragment of the factor Va heavy chain (residues 307 to 506), produced by activated protein C, and the 97-kDa fragment of the factor Va heavy chain (residues 1 to 643) were released more rapidly after simvastatin treatment. The antithrombotic actions of simvastatin showed no relationship to its cholesterol-lowering action. CONCLUSIONS: Simvastatin treatment depresses blood clotting, which leads to reduced rates of prothrombin activation, factor Va generation, fibrinogen cleavage, factor XIII activation, and an increased rate of factor Va inactivation. These effects are not related to cholesterol reduction.

Adult↗

Activity of blood coagulation factor XIII as a prognostic indicator in patients with Henoch-Schönlein purpura. Efficacy of factor XIII substitution.

UNLABELLED: Determination of coagulation Factor XIII (F XIII)-related parameters in 21 patients with Henoch-Schönlein purpura documented a significant decrease of F XIII activity as well as of the F XIII-related antigenic determinants. Subgroup analysis with regard to the clinical symptoms showed an even further decrease of these parameters in patients with gastrointestinal complications. Stimulated by these findings a substitution therapy with a F XIII concentrate was initiated in those patients whose F XIII activity in plasma remained low and who developed severe abdominal pain accompanied by persisting gastrointestinal bleeding. This therapeutic approach not only corrected the laboratory data, but more important led to a cessation of pain and bleeding. A rapid decrease of F XIII levels after transfusion below 40 U/ml was indicative of relapse of abdominal symptoms, while increasing values were associated with the recovery of the patients. IN CONCLUSION: F XIII activity determinations appear to have a predictive value in patients with Henoch-Schönlein purpura, and the administration of F XIII concentrates may contribute to the improvement of gastrointestinal complications.

Child↗

Role of blood coagulation factor XIII in patients with acute pulmonary embolism. Correlation of factor XIII antigen levels with pulmonary occlusion rate, fibrinogen, D-dimer, and clot firmness.

In patients with acute pulmonary embolism (PE), pulmonary occlusion rate is directly related to D-dimer and inversely related to fibrinogen levels. The role of coagulation factor XIII (FXIII) levels in acute venous thromboembolism is not known. A total of 120 consecutive patients with suspected PE and VIDAS D-dimer levels >500 micro g/L were investigated by helical computed tomography (CT). Pulmonary occlusion rate was assessed by CT using the modified Miller index. D-dimer, fibrinogen, and FXIII A- and B-subunit antigen levels were taken on admission. Thrombelastography (TEG) was performed in a subset of patients (n = 12). The 71 patients with PE had lower FXIII A-subunit levels than the 49 patients with excluded PE (78.6 +/- 24.5% vs. 91.3+/-28.8%, p=0.01). In both groups, FXIII A-subunit was inversely related to D-dimer levels. FXIII A-subunit correlated with fibrinogen levels in patients with PE but not in patients without PE. FXIII A-subunit decreased with increasing pulmonary occlusion rate. The risk of PE was increased in the presence of A-subunit levels < 60% (OR 7.0 [95% CI 1.4-35.3], p = 0.019). Clot firmness determined by TEG was lower in patients with PE than in patients without PE. In patients with PE, circulating FXIII A-subunit is decreased compared to patients with suspected but excluded PE. The higher the clot burden within the pulmonary arteries the lower the FXIII antigen. In these patients, direct relation of FXIII A-subunit to fibrinogen levels argues for significant consumption of these coagulation factors in PE. This consumption of FXIII can also be detected by a global coagulation test like TEG.

Acute Disease↗

Factor XIII.

1. Activated factor XIII is the enzyme that covalently cross-links fibrin monomers into fibrin polymers and results in increased clot strength and resistance of the clot to fibrinolysis. 2. Small amounts (greater than 1% of normal) of factor XIII are necessary for normal in vitro and in vivo activity. 3. Factor XIII deficiency is a rare autosomal recessive illness in which a hemorrhagic diathesis is caused by the virtual absence of the active a subunit of factor XIII. Approximately 100 cases have been described. 4. The disease in homozygotes is characterized by umbilical stump bleeding, a high incidence of fetal wastage, delayed soft tissue hemorrhage, and a high incidence of intracranial bleeding. The heterozygote is asymptomatic. 5. This paper calls attention to the apparent high incidence of oligospermia and small testes seen in homozygote males. Otherwise secondary sex characterics are normal. 6. Because there is no abnormality in thrombin generation and conversion of fibrinogen to fibrin, route coagulation tests (prothrombin time, partial thromboplastin time, thrombin time, etc.) are normal. Platelet function tests are normal. 7. Clots made from recalcified plasma severely deficient in factor XIII are soluble in 5 M urea or 1% monochloroacetic acid. These screening tests are simple and nearly pathognomonic of the illness. 8. More sophisticated and quantitative tests (e.g., dansylcadaverine incorporation) are available for definitive diagnosis and heterozygote detection. 9. Replacement treatment of the illness is simple, effective, and relatively inexpensive. Due to the long half-life of infused factor XIII and the small amounts necessary for normal hemostasis, prophylaxis is feasible and encouraged.

Adult↗