Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein C(PC) is the zymogen of a serine protease which regulates blood coagulation by inactivating activated blood coagulation factors V and VIII. We investigated the plasma level of PC in patients with deep vein thrombosis (DVT, n = 50), Buerger's disease (n = 34), arteriosclerosis obliterans (n = 37) and myocardial infarction (n = 17). PC in plasma was determined by rocket immunoelectrophoresis using a monospecific anti-PC antiserum raised in rabbits. Our study indicated that only in DVT the level of PC was decreased in comparison with the normal control (p less than 0.05). This decrease may be accounted for by increased utilization of PC for the regulation of continuously activated blood coagulation mechanism possibly ongoing in patients with DVT. On the other hand, among the patients with the DVT, we found a homozygous PC deficiency combined with a heterozygous dysplasminogenemia in a 22-year old male who had been suffering from recurrent venous thrombosis since the age of 14. Although the homozygous form of PC deficiency has been reported to be closely associated with fatal thrombotic disorders including purpura furminans during the neonatal period, the patient reported here had surprisingly survived the neonatal period and the childhood without any clinical manifestation relevant to thrombosis.
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PMID:[Protein C dynamics in peripheral arterial occlusive diseases and myocardial infarction: association of homozygous protein C deficiency with heterozygous dysplasminogenemia found among patients with deep vein thrombosis]. 375 30

Human activated protein C (APC) is a plasma serine protease that possesses amidolytic and anticoagulant activity. The rate at which the amidolytic and anticoagulant activity of APC was neutralized in normal plasma was essentially identical to that observed in plasma obtained from four individuals with combined Factor V/VIII deficiency disease. Incubation of radioiodinated APC with either normal human plasma or the combined Factor V/VIII-deficient plasmas resulted in the formation of a stable complex (Mr = 96,000) of the enzyme and a plasma protein as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Pretreatment of the radiolabeled APC with diisopropyl fluorophosphate prevented the formation of the enzyme-protein complex. On the basis of its ability to form a complex with radiolabeled APC, the APC-binding protein was purified to homogeneity from normal human plasma by ammonium sulfate fractionation, heparin-agarose chromatography, and QAE-Sephadex A-50 chromatography. The APC-binding protein (Mr = 54,000) is a glycoprotein, and possesses an amino-terminal sequence of Gly-Arg-Thr-Cys-Pro-Lys-Pro-Asp. The amino-terminal sequence of the APC-binding protein exhibited considerable homology with bovine colostrum inhibitor and pancreatic trypsin inhibitor, but no apparent sequence homology with the plasma serine protease inhibitors. Affinity-purified antibody against APC-binding protein immunoprecipitated a complex of radiolabeled APC and native APC-binding protein from normal human plasma. Complex formation was virtually eliminated in plasma immunodepleted of the APC-binding protein. Quantitative electroimmunoassay indicated essentially equal levels of APC-binding protein antigen in normal plasma compared with plasma from four patients with combined Factor V/VIII deficiency disease.
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PMID:Evidence of normal functional levels of activated protein C inhibitor in combined Factor V/VIII deficiency disease. 629 39

Protein C is a precursor to a serine protease that is present in mammalian plasma. In its activated form, it readily inactivates factor Va and factor VIIIa, two proteins that participate as cofactors in the blood coagulation cascade. In the present studies, a lambda gt11 library containing cDNA inserts prepared from human liver mRNA has been screened with an antibody to human protein C. Seven positive clones were isolated from 2 X 10(6) phage and were plaque-purified. The cDNA inserts of two of these phage were sequenced and shown to code for human protein C. Each cDNA insert coded for a portion of the light chain of the molecule, a connecting region, the heavy chain, a stop codon, a 3'-noncoding region, and a poly(A) tail. The length of the noncoding sequence on the 3' end differed in the two clones, but each contained a processing or polyadenylylation signal followed by a poly(A) tail. The amino acid sequence as determined from the cDNA indicates that protein C is synthesized as a single-chain polypeptide containing the light chain and the heavy chain connected by a dipeptide of Lys-Arg. The single-chain molecule is then converted to the light and heavy chains by cleavage of two or more internal peptide bonds. In plasma, the heavy and light chains of protein C are linked together by a disulfide bond. The amino acid sequence of human protein C shows a high degree of homology with that of the bovine molecule. The DNA sequence coding for the catalytic region near the active site serine in human protein C also showed a high degree of DNA and amino acid sequence identity with prothrombin, factor IX, and factor X, three of the other vitamin K-dependent serine proteases that are present in plasma.
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PMID:Characterization of a cDNA coding for human protein C. 658 23

More than 100 chromogenic and fluorogenic peptide substrates are now available for the evaluation of coagulation and related parameters. Many of these substrates exhibit undesirable physical properties, such as insolubility, surface adsorption, and interaction with endogenous plasma proteins. Some of these substrates are capable of inhibiting serine protease generation during activation in the global assay. In order to develop synthetic chromogenic substrates with desirable physical and biochemical characteristics, modified amino acids, such as CHG, CHT, and Nleu, have been utilized. Similarly, to provide a favorable molecular environment to facilitate enzyme and synthetic substrate interactions, various molecular manipulations, such as the introduction of bulky groups, is helpful in developing substrates for protein Ca and C1-esterase. Substrates for Factor Xa, CH3-O-CO-CHG-Arg-pNA (bovine Xa, Km 2.5 X 10(-4) M; human, Km 3.5 X 10(-4) M); thrombin, H-D-CHT-Ala-Arg-pNA (bovine thrombin, Km 3 X 10(-6) M; human thrombin, Km 6 X 10(-6) M); plasmin, H-D-Nleu-CHT-Lys-pNA (human plasmin, Km 2.2 X 10(-5) M) were found to have identical or superior biochemical characteristics to the earlier substrates. These newer substrates were found to be more soluble (greater than 5 X 10(-4) M) in physiologic buffer, less susceptible to autoamidolysis at reaction conditions, and did not produce opacity of the test solution in final concentrations of 5 X 10(-4) M. Comparable results on normal and pathologic plasma samples were obtained in various laboratory assays that utilize currently available substrates for Factors Xa and IIa, kallikrein, and plasmin (R = greater than 0.9). We propose that prior to the application of a new synthetic substrate in a given assay, a careful biochemical and physical screening of the substrate, the assay conditions, and the interaction of substrates with plasma proteins is highly desirable.
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PMID:Newer synthetic peptide substrates in coagulation testing: some practical considerations for automated methods. 665 59

Protein C is the zymogen of a vitamin K-dependent serine protease involved in blood coagulation. In the absence of protein C the inactivation of activated factors V and VIIIC is impaired, and the fibrinolytic capacity of the circulating blood is reduced. These conditions promote excessive fibrin formation and thus constitute a risk factor for thrombosis. Using an immunologic assay for protein C, we identified 18 patients (11 male and 7 female) in three unrelated Dutch families as fulfilling the criteria for an isolated protein C deficiency. In 12 patients who were not receiving oral anticoagulant treatment the mean protein C antigen concentration was 0.48 +/- 0.09 U per milliliter (+/- S.D.), and in 6 patients who were receiving adjusted doses of oral anticoagulants and had stable anticoagulation, the mean value was 0.17 +/- 0.05 U per milliliter. (The value in healthy subjects is 0.98 +/- 0.19 U per milliliter.) Fourteen of the 18 patients had a history of venous thromboembolism, with superficial thrombophlebitis as the hallmark of this condition (in 13 patients). These data are consistent with an autosomal dominant trait with variable expressivity.
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PMID:Congenital protein C deficiency and venous thromboembolism. A study of three Dutch families. 668 22

The coagulation protein Factor Va forms the receptor for the serine protease Factor Xa at the platelet surface. This membrane-bound complex of Factor Va and Factor Xa plus calcium constitutes the enzymatic complex prothrombinase, which effects the conversion of prothrombin to the clotting enzyme, thrombin. Studies were undertaken to investigate the proteolytic events accompanying the inactivation of platelet-bound Factor Va by activated protein C as well as the ability of Factor Xa to protect Factor Va from activated protein C inactivation. During the course of these studies, observations were made which indicated that Factor Va was also cleaved by both a platelet-associated protease, as well as Factor Xa. When Factor Va was incubated with washed platelets, electrophoresis and autoradiography of solubilized platelet pellets indicated that three Factor Va peptides were associated with the platelet: component D (Mr = 94,000), component E (Mr = 74,000), and a 90,000-dalton peptide (component D') which appeared with time as the result of a platelet-associated protease cleavage of component D. The Factor Va peptides bound to platelets were proteolytically inactivated by activated protein C, resulting in five peptide products, all of which remained associated with the platelet-membrane surface. Factor Va was protected from activated protein C proteolysis by complex formation with Factor Xa or active site-blocked Factor Xa. However, active Factor Xa cleaved platelet-bound Factor Va to peptide products which also remained associated with the platelet. Whereas activated protein C rapidly cleaved components D and D' with secondary cleavages occurring in component E, Factor Xa rapidly cleaved component E with secondary cleavages occurring in components D and D'. The Factor Xa-cleaved Factor Va is catalytically functional. To determine whether cleavage was necessary for function, prothrombin conversion reaction mixtures were monitored for thrombin formation and Factor Va cleavage with time in a defined phospholipid vesicle model system. The results indicated that Factor Xa cleavage of Factor Va is not essential for Factor Va activity but may promote its ability to function in the prothrombinase complex.
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PMID:Proteolytic alterations of factor Va bound to platelets. 684 22

Factor Xa binds to a receptor available on the platelet surface after the release reaction. The receptor consists of phospholipid and factor V. Factor Xa bound to the receptor catalyses the activation of prothrombin effectively. The effects of bovine protein C, a vitamin-K-dependent zymogen of a serine protease, on prothrombin activation by platelet-bound bovine factor Xa has been studied. Protein C was found to be activated (protein Ca) by thrombin formed in the prothrombin-platelet-factor Xa incubation. Protein Ca in contrast to the zymogen, protein C, or protein Ca inactivated with diisopropylphosphofluoridate inhibited prothrombin activation by factor Xa in the presence of platelets. protein Ca was found to destroy the receptor by proteolysis whereas direct binding of protein Ca to the receptor could not be demonstrated. The inhibition by protein Ca could be monitored as a parallel decrease in factor Xa binding and prothrombin activation. The receptor was protected by factor Xa from proteolysis by protein Ca. Protein Ca was also found to inhibit the interaction between prothrombin and the factor Xa platelet receptor. These results indicate that protein C after activation may have a role as a regulator of prothrombin activation in vivo.
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PMID:Inhibitory effect of activated protein C on activation of prothrombin by platelet-bound factor Xa. 689 81

Activated protein C is a potent anticoagulant and profibrinolytic enzyme that can be derived from the vitamin-K-dependent serine protease zymogen, protein C, by the action of thrombin. Protein C antigen concentration was determined in plasmas from normals (n = 40) and from 38 patients with intravascular coagulation as evidenced by positive FDP (greater than micrograms/ml). Plasma protein C was 4 micrograms/ml in normals and was significantly depressed (less than 2 SD below the mean of normals) in 19 of the 38 patients. Of 15 patients with suspected intravascular coagulation but normal FDP, protein C was decreased in 5 individuals; 3 of these 5 patients had liver disease. Based on these results, we suggest that extensive activation of the coagulation system in vivo causes a significant consumption of protein C, presumably due to its activation by thrombin and subsequent clearance.
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PMID:Protein C, an antithrombotic protein, is reduced in hospitalized patients with intravascular coagulation. 689 90

The human anticoagulant factor, Protein C, is a plasma glycoprotein that has reported anti-ischaemic and anti-inflammatory properties. To explore potential mechanisms for these reported activities, we examined the effect of Protein C on the process of cell adhesion to vascular endothelial cells, which plays a critical role during inflammatory responses. We show that both human plasma-derived and human cell-produced recombinant Protein C inhibit E-selectin-mediated cell adhesion. This effect was not mediated through the serine protease activity of Protein C, but through its carbohydrates. Using oligosaccharides isolated from human cell-produced Protein C, we have defined a polylactosamine structural determinant that inhibits adhesion. This uncharged determinant appears to be a more potent ligand for E-selectin than the sialylated Lewis X antigen. Our data suggest a potential mechanism for the reported anti-inflammatory effects of Protein C and describe a new ligand for selectin-mediated adhesion.
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PMID:Human protein C inhibits selectin-mediated cell adhesion: role of unique fucosylated oligosaccharide. 751 10

Initiation of blood coagulation occurs when the plasma serine protease factor VIIa (fVIIa) binds to its cell-surface receptor/cofactor, tissue factor (TF). This binding interaction mediates a large enhancement in both the proteolytic activity and the amidolytic activity (hydrolysis of small peptidylamide substrates) of fVIIa. This necessitates local changes in the catalytic center of fVIIa of which little is understood. Studies with thrombin and activated protein C have demonstrated that residue E192 (chymotrypsinogen numbering system) near the active site of these proteases is an important determinant for substrate and inhibitor specificity. By homology, residue 192 in fVIIa is K, bringing into question the potential role of this residue in fVIIa. We have prepared two mutants of fVIIa in which K192 has been replaced by either Q (as in factors IX and X) or E (as in thrombin). Both mutants were found to be defective in clotting: fVIIK 192Q was 44% active, while fVIIK192E was completely ineffective. This defect was attributable to proportional decreases in specificity constants for activation of factor X. Although both mutant enzymes were catalytically competent with respect to amidolytic activity, the selectivity of fVIIaK192E was greatly altered. Inhibition of both mutants by the TF pathway inhibitor (TFPI) and bovine pancreatic trypsin inhibitor (BPTI) was also drastically altered. Neither mutant was inhibited by TFPI, while fVIIaK192Q was inhibited by BPTI better than wild-type fVIIa. In contrast, fVIIaK192E was poorly inhibited by BPTI and made more refractory to inhibition when bound to TF. These results suggest a potential role for K192 in governing the substrate and inhibitor specificities of fVIIa.
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PMID:Alteration of the substrate and inhibitor specificities of blood coagulation factor VIIa: importance of amino acid residue K192. 754 28


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