Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the effect of divalent metal ions on the proteolytic cleavage and activation of platelet Factor XIII by thrombin and trypsin. In the absence of metal ions (5 mM EDTA), trypsin and thrombin rapidly degraded platelet Factor XIII (80 kDa) to low-molecular-mass peptides (50-19 kDa) with simultaneous loss of transglutaminase activity. Divalent metal ions protected Factor XIII from proteolytic inactivation with an order of efficacy of Ca2+ greater than Zn2+ greater than Mg2+ greater than Mn2+. Calcium (2 mM) increased by 10- to 1000-fold the trypsin and thrombin concentrations required to degrade Factor XIII to a 19-kDa peptide. Factor XIIIa formed by thrombin in the presence of 5 mM EDTA had one-half the specific activity of Factor XIIIa formed in the presence of calcium. Factor XIII was cleaved by trypsin in the presence of 5 mM Ca2+ to a 51 +/- 3-kDa fragment that had 60% of the original Factor XIIIa activity. A similar tryptic peptide formed in the presence of 5 mM EDTA did not have transglutaminase activity. In the presence of 5 mM Mg2+, thrombin cleaved Factor XIII to a major 51 +/- 3-kDa fragment that had 60% of the Factor XIIIa activity. Mn2+ (0.1-5 mM) limited trypsin and thrombin proteolysis. The resulting digest containing a population of Factor XIII fragments (50-14 kDa) expressed 50-60% transglutaminase activity of Factor XIIIa. Factor XIII was fully activated by both trypsin and thrombin in the presence of 5 mM Zn2+, resulting in two fragments of 76 and 72 kDa. We conclude that the binding of divalent metal ions to platelet Factor XIII induces conformational changes in the protein that alter its susceptibility to proteolysis and influence the expression of transglutaminase activity.
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PMID:The binding of divalent metal ions to platelet factor XIII modulates its proteolysis by trypsin and thrombin. 289 89

Factor XIII (plasma transglutaminase, fibrin stabilizing factor) is a glycoprotein that circulates in blood as a tetramer (a2b2) consisting of two a and two b subunits. The primary structures of the a and b subunits of human factor XIII have been reported by a combination of cDNA cloning and amino acid sequence analysis. To establish the gene structure of the a subunit for factor XIII, several human genomic libraries were screened by using the cDNA encoding the a subunit as a probe. Among approximately equal to 5 x 10(7) recombinant phage, 121 have been shown to contain an insert encoding a portion of the a subunit. Twenty-five unique clones were then characterized by restriction mapping, Southern blotting, and DNA sequencing. Overlapping clones encoding the a subunit of factor XIII span greater than 160 kilobases. The gene was found to contain 15 exons separated by 14 introns. All the sequences of the introns at the intron-exon boundaries were GT-AG, which are the same as those found in other eukaryotic genes. DNA sequence analysis revealed that the activation peptide released by thrombin, the active site cysteine region, the two putative calcium-binding regions, and the thrombin cleavage site leading to inactivation are encoded by separate exons. This suggests that the introns may separate the a subunit into functional and structural domains. A comparison of the amino acid sequence deduced from the genomic DNA sequence with those deduced from cDNA or determined by amino acid sequence analysis of the plasma and placental proteins revealed apparent amino acid polymorphisms in six positions of the polypeptide chain of the a subunit.
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PMID:Characterization of the gene for the a subunit of human factor XIII (plasma transglutaminase), a blood coagulation factor. 290 Oct 91

While the transglutaminase activity is associated exclusively with the thrombin-cleaved a chains of plasma Factor XIII, there is little information regarding the role of the b-chains. The present investigations were undertaken to clarify the role of the b-chains during proteolytic activation of plasma factor XIII a-chains. The a-chains of platelet Factor XIII (a2) were extremely sensitive to alpha-thrombin proteolysis, especially in the presence of 5 mM EDTA, resulting in two major fragments with molecular masses 51 +/- 3 kDa and 19 +/- 4 kDa. Furthermore, fibrin enhanced the alpha-thrombin proteolysis of thrombin-cleaved platelet Factor XIII a-chains in presence of CaCl2 or EDTA, resulting in several peptide fragments with molecular masses from 51 +/- 3 kDa to 14 +/- 4 kDa. By contrast, thrombin-cleaved a-chains of plasma Factor XIII (a2b2) were not further degraded by alpha-thrombin in presence of 5 mM EDTA. Even in the combined presence of 5 mM EDTA and 0.1 mg/ml fibrin, alpha-thrombin proteolysis of plasma Factor XIIIa was limited to the formation of a 76 kDa fragment (= Factor XIIIa), a 51 +/- 3 kDa fragment and trace amounts of a 14 +/- 4 kDa species. Platelet Factor XIII proteolyzed by 500 nM alpha-thrombin in presence of 5 mM EDTA expressed less than 20% of enzymatic activity obtained when platelet Factor XIII was activated in presence of 5 mM CaCl2. In contrast, plasma Factor XIII activated by 500 nM apha-thrombin in presence of 5 mM EDTA expressed nearly 65% of original transglutaminase activity. Likewise, when plasma Factor XIII was proteolyzed by 100-1000 nM gamma-thrombin in presence of 5 mM CaCl2 or 5 mM EDTA, maximal transglutaminase activity was observed. However, when platelet Factor XIII was similarly treated with gamma-thrombin in presence of 5 mM EDTA, only one-half the original transglutaminase activity was obtained. The b-chains thus appear to mimic the function of Ca2+ in preserving transglutaminase activity of thrombin-cleaved a-chains. The b-chains of plasma Factor XIII were not degraded by either alpha- or gamma-thrombin treatment, in presence of 5 mM EDTA or 5 mM CaCl2. Both platelet and plasma Factor XIII a-chains were degraded by trypsin to fragments with molecular masses of 51 +/- 3 kDa and 19 +/- 4 kDa in presence of 5 mM CaCl2 and to fragments with molecular masses of 19 +/- 4 kDa and lower, in presence of 5 mM EDTA.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:b-chains prevent the proteolytic inactivation of the a-chains of plasma factor XIII. 290 Dec 75

Platelets contain factor XIII, an A subunit zymogen form of transglutaminase (TGase), that is activated by thrombin. In addition a thrombin-independent TGase (A#) was observed. A# was formed in platelet preparations lysed at acid pH, and its generation inhibited by protease inhibitors and alkaline pH. When maximal A# activity was generated in acidified lysates no further TGase activity could be induced by subsequent treatment with thrombin. Both FXIII zymogen and A# copurified as for FXIII, from either alkaline or from acidified platelet lysates respectively, by the conventional procedure. The pH optima, Km's for NN dimethyl casein, molecular weights, heat lability of active forms, requirements for calcium and reducing agents, and immunological characteristics of both TGases were the same. Studies with inhibitor substrates suggested that a thrombin-like cathepsin C or carboxypeptidase was responsible for A# formation. Purified FXIII zymogen could be activated directly by cathepsin C. Thus, the predominant, and probably only, TGase of platelets is factor XIII, which may be activated either by thrombin or by endogenous platelet acid protease(s).
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PMID:Thrombin-independent activation of platelet factor XIII by endogenous platelet acid protease. 290 73

Purified platelet Factor XIII was radioiodinated and then partially degraded by thrombin or trypsin, and a fibrin-binding fragment was identified by autoradiography and immunoblotting following separation by SDS/polyacrylamide-gel electrophoresis. Limited proteolysis of 125I-Factor XIII by thrombin or trypsin produced an 125I-51 kDa fragment and an unlabelled 19 kDa fragment. The 51 kDa fragment was purified by h.p.l.c. on a TSK-125 gel-filtration column. Partial amino acid sequence analysis of the 51 kDa fragment indicated that it was similar in sequence to the Gly38-Lys513 segment in placental Factor XIII a-chain. More than 70% of the 51 kDa fragment bound to fibrin, whereas the 19 kDa fragment did not bind. The active site was localized to the 51 kDa fragment since this fragment expressed transglutaminase activity, cross-linked fibrin and fibrinogen and incorporated iodo[14C]acetamide into the active-site cysteine residue. Isolation of a fibrin-binding fragment expressing transglutaminase activity demonstrates that each a-chain of the dimeric Factor XIIIa could function independently to cross-link fibrin. The fibrin-binding site could play an important role in localizing Factor XIIIa to the fibrin clot.
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PMID:Isolation of a fibrin-binding fragment from blood coagulation factor XIII capable of cross-linking fibrin(ogen). 306 50

Fibrinoligase, the fibrin cross-linking enzyme, transiently appearing during the course of coagulation in normal blood, was shown to catalyze the incorporation of a fluorescent amine, monodansylcadaverine [or N-(5-aminopentyl)-5-dimethylamino-1-naphthalene-sulfonamide] into casein. The reaction provided the basis of a sensitive fluorimetric method for measuring the activity of the enzyme (and also of similar other transpeptidases, such as transglutaminase). In tests involving plasma, certain difficulties had to be overcome which were mainly due to the fact that the enzyme itself does not occur in citrated plasma. Only its precursor (fibrin-stabilizing factor or factor XIII) is present, still requiring limited proteolytic activation by thrombin. Thus, in order to measure amine incorporation with plasma as a source of the factor, thrombin must be added. This necessitated a differential desensitization of the intrinsic fibrinogen so that the latter could not clot and could not thereby interfere with amine incorporation. Also, the thrombin-inactivating capacity of plasma had to be saturated to enable full conversion of the factor to the transpeptidase. Concentrations of casein, monodansylcadaverine, calcium, and hydrogen ions were chosen to permit almost maximal velocity of amine incorporation. A linear relationship with regard to plasma concentration could be obtained only under such conditions. No similar assay is presently available for quantitatively evaluating fibrin-stabilizing factor levels in plasma.The amine incorporation test was applied to a clinical case of hereditary total fibrin-stabilizing factor deficiency. The effect of transfusion therapy was studied, and some of the patient's relatives were examined. Whereas a paternal aunt and uncle gave values well within the normal range, a brother and the mother proved to be partially deficient and could be considered as heterozygous carriers. The father appeared to have a reduced level of fibrin-stabilizing factor, though not quite as low as the other two relatives. Two infusions (1 liter each) of fresh normal plasma, administered about 26 hr apart, brought levels in the patient's plasma close to those found in the mother and brother. The corrective power of the transfusions, however, rapidly declined within 5-6 days. Futility of the last transfusion could be ascribed to the appearance of a neutralizing antibody directed against the precursor stabilizing factor, a serious complication. General diagnostic versatility and potential of the quantitative amine incorporation assay with plasma is discussed.
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PMID:Diagnostic and genetic studies on fibrin-stabilizing factor with a new assay based on amine incorporation. 497 30

The action of human plasma factor XIIIa (thrombin-activated blood coagulation factor XIII) and guinea pig liver transglutaminase on purified caseins, fibrin, the derivatized gamma chain of fibrin, and a number of synthetic glutamine peptides, and peptide derivatives is reported. There are wide variations in the properties of the individual proteins and peptides as substrates for amine incorporation by the two transglutaminases. beta-Casein and several of its derivatives are excellent substrates for factor XIIIa. However, beta-casein is a relatively poor substrate for the liver enzyme. The primary site of amine incorporation by factor XIIIa in beta-casein was identified as glutamine 167. This was accomplished by labeling with fluorescent amine followed by proteolytic digestion and identification of labeled peptides. An 11-residue peptide and a 15-residue peptide, each containing 1 glutamine residue and each modeled after the primary site of amine incorporation in beta-casein, were prepared. A 13-residue peptide modeled after the primary crosslinking site in fibrin gamma chain was also prepared. Each of these polypeptides proved to be an efficient substrate for factor XIIIa and displayed significantly better substrate properties than a number of small glutamine peptide derivatives that are good substrates for liver transglutaminase.
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PMID:Structural features of glutamine substrates for human plasma factor XIIIa (activated blood coagulation factor XIII). 610 25

Plasma, serum and the main proteins involved in the final steps of blood coagulation, fibrinogen, thrombin and plasma transglutaminase, have been tested for their ability to inhibit cell transformation and/or to induce reversion of the transformed to the normal phenotype in RSV-infected chicken embryo fibroblasts. The results obtained show that plasma, and not serum, fibrinogen, when converted to fibrin by thrombin, and activated transglutaminase alone prevent focus appearance and cause reversion of transformed to normal cell morphology.
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PMID:Inhibition of Rous sarcoma-virus-induced transformation by proteins involved in blood coagulation. 610 67

This paper is intended as a background to the topic of transglutaminases, while focusing on current ideas regarding the biological roles of these enzymes. Specifically, the following topics are discussed: geometry of forming gamma-glutamyl-epsilon-lysine cross-linked structures; energetic considerations; the gamma-glutamyl-epsilon-lysine cross-link; amine incorporation assays; artefactual incorporation of amines in cells and tissue homogenates; synthetic substrate systems; regulation of transglutaminase activities; strategies for probing transglutaminase-mediated events in biological systems; the blood clotting paradigm; transglutaminase and cell aging: the Ca2+-enriched human erythrocyte; transglutaminase and cell activation: the thrombin-stimulated human platelet and the fertilized sea urchin egg.
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PMID:Transglutaminases. 614 56

Transglutaminases (transamidases; endo-gamma-glutamine: zeta-lysine transferases) are calcium-dependent enzymes, which cross-link proteins by introducing covalent zeta-(gamma-glutaminyl)lysine pseudopeptide bonds between the molecules. The distribution and characteristics of transglutaminase in both human and rabbit eyes have been studied. Transglutaminase activity was measured with an isotope technique based on the enzyme catalysed incorporation of 14C-putrescine into casein. Electrophoretic characteristics were studied using agarose gel electrophoresis combined with a specific fluorescent activity staining procedure based on the transglutaminase catalysed incorporation of monodansylthiacadaverine into casein. A thrombin-independent enzyme, indistinguishable from the guinea pig liver transglutaminase with regard toi electrophoretic mobility, was found in the choroid/pigment epithelium and ciliary body of the human eye while the lens, retina, iris and vitreous humour did not contain detectable amounts. The lens and the choroid/pigment epithelium of the rabbit eye tissues contained high activities while the activity in the extract from the combined ciliary body/iris was low but measurable.
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PMID:Localization and characteristics of transglutaminase in the rabbit and human eye. 617 50


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