Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new fluorogenic peptide substrate for plasmin, 7-(N-succinoylalanylphenylalanyl-lysylamido)-4-methylcoumarin trifluoroacetate salt, was prepared that can be used in a simple and direct assay. The results obtained by the assay method are linear over a wide range of enzyme concentrations and sensitive enough to detect as little as 10(-5) CTA units of plasmin. By making use of the inhibitor Trasylol and the differences in kinetic constants, plasmin can be specifically assayed even in the presence of the plasminogen activator thrombin, as well as in culture fluids from HeLa cells.
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PMID:A new fluorogenic substrate for plasmin. 16 7

The fibrinolytic activity of proteases secreted by chick embryo fibroblasts infected with Rous sarcoma virus was studied by use of a procedure in which a fibrin clot was formed with highly purified fibrinogen and thrombin above the cell layer. This procedure results in the formation of fibrin that is apparently a more suitable substrate for studies on fibrinolysis than is fibrin prepared by other methods. Since neither plasminogen nor serum were included in the assay system in the present studies, the fibrinolytic activity observed cannot be ascribed to the conversion of the plasminogen in serum to plasmin by a plasminogen activator produced by transformed cells. Our procedure, therefore, measures proteolytic activities other than those reported by previous investigators. Maintenance of some of the transformed phenotypes of Rous sarcoma virus transformed chick embryo fibroblasts such as morpholigical change and increased rate of glucose uptake apparently does not depend on the presence of plasminogen in the culture medium.
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PMID:Plasminogen-independent fibrinolysis by proteases produced by transformed chick embryo fibroblasts. 16 84

We have observed that treatment of rabbit synovial fibroblasts with proteolytic enzymes can induce secretion of collagenase (EC 3.4.24.7) and plasminogen activator (EC 3.4.21.-). Cells treated for 2-24 hr with plasmin, trypsin, chymotrypsin, pancreatic elastase, papain, bromelain, thermolysin, or alpha-protease but not with thrombin or neuraminidase secreted detectable amounts of collagenase within 16-48 hr. Treatment of fibroblasts with trypsin also induced secretion of plasminogen activator. Proteases initiated secretion of collagenase (up to 20 units per 10(6) cells per 24 hr) only when treatment produced decreased cell adhesion. Collagenase production did not depend on continued presence of proteolytic activity or on subsequent cell adhesion, spreading, or proliferation. Routine subculturing with crude trypsin also induced collagenase secretion by cells. Secretion of collagenase was prevented and normal spreading was obtained if the trypsinized cells were placed into medium containing fetal calf serum. Soybean trypsin inhibitor, alpha(1)-antitrypsin, bovine serum albumin, collagen, and fibronectin did not inhibit collagenase production. Although proteases that induced collagenase secretion also removed surface glycoprotein, the kinetics of induction of cell protease secretion were different from those for removal of fibronectin. Physiological inducers of secretion of collagenase and plasminogen activator by cells have not been identified. These results suggest that extracellular proteases in conjunction with plasma proteins may govern protease secretion by cells.
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PMID:Proteases induce secretion of collagenase and plasminogen activator by fibroblasts. 20 72

The tumor promoter phorbol myristate acetate (PMA) induces the production of the serine protease plasminogen activator (PA) in cultures of normal chick embryo fibroblasts (CEF) and synergistically enhances PA production in Rous sarcoma virus-transformed chick embryo fibroblasts (RSVCEF). Following PMA treatment of serum-free RSVCEF cultures, PA induction is accompanied by distinct morphological changes, including enhanced cell clustering and the formation of dense cellular aggregates. These alterations in the morphology of the PMA-treated transformed cells are inhibited by several protease inhibitors, including leupeptin, NPGB, SBTI, benzamidine and DFP, the specific inhibitor of serine enzymes. A number of protease inhibitors are ineffective in preventing the PMA-induced morphological changes; these include inhibitors of trypsin, chymotrypsin, elastase, thrombin and, most importantly, plasmin. The use of a fluorescent substrate to assay PA directly demonstrated that the pattern of inhibiton of PA activity correlates exactly with the inhibition of morphological changes. The of 3H-DFP to label and characterize serine zymes in the culture fluid from PMA-treated cells further indicated that PA is the serine protease responsible for the morphological changes. Thus PA itself can catalytically alter cellular behavior in culture independent of plasminogen, until not its only known natural substrate.
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PMID:Phorbol ester-induced morphological changes in transformed chick fibroblasts: evidence for direct catalytic involvement of plasminogen activator. 22 74

During normal pregnancy, the concentrations of many of the clotting factors rise, thereby increasing the potential to generate fibrin. There is also evidence of increased thrombin activity during normal pregnancy which sharply increases during placental separation. Antithrombin III, the main inhibitor of thrombin and activated factor X, shows no compensatory rise during pregnancy but increases during the puerperium. Plasminogen and antiplasmin concentrations rise during pregnancy but systemic fibrinolytic activity, as measured by the euglobulin lysis time, is markedly depressed during pregnancy; the reduced fibrinolytic activity returns to non-pregnant values very soon after delivery. The loss of fibrinolytic activity is presumed to be loss of plasminogen activator, because when this is added in excess in the urokinase sensitivity test, the fibrinolytic response is normal. The capacity for localized fibrinolytic activity is not lost, however, because fibrinolytic degradation products are slightly raised during pregnancy. The overall pattern is one of increased coagulant and reduced fibrinolytic capacity during pregnancy which may protect the pregnant woman against the haemostatic challenge of placental separation.
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PMID:Blood clotting and fibrinolysis in pregnancy. 38 69

The vascular endothelium is a rich source of plasminogen activator (PA) and thus of blood vessel-associated fibrinolytic activity. Cultured bovine aortic endothelial cells were employed to determine if components of the coagulation system interact with the endothelium to modify expression of this activity. The addition of thrombin to these cultures led to a rapid decline in intracellular PA activity, with as little as 3 ng/ml, or 0.1 nM thrombin causing a 50% decrease within 30 min. Thrombin inactivated with diisopropylflurophosphate or hirudin did not elicit the response. Although control cultures secreted high levels of PA, no PA activity could be detected in the media surrounding the thrombin-treated cells. This loss of activity did not appear to result from direct inactivation of PA by thrombin. These observations indicate that the fibrinolytic potential of cultured endothelial cells is rapidly suppressed by trace amounts of thrombin. The generation of thrombin at sites of vascular injury may have a similar effect on the endothelium.
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PMID:Effect of thrombin on the fibrinolytic activity of cultured bovine endothelial cells. 44 60

The saliva of the tsetse, Glossina morsitans morsitans Westwood, has antithrombin anticoagulant activity and inhibits thrombin's esterolytic activity. It has no other detectable anticoagulant properties. The anticoagulant elutes in a single peak on Sephadex fraction, is immediately acting, heat and storage stable, and has a molecular weight of 11-13,000. Unlike heparin it is not neutralized by protamine sulphate or toluidine blue and does not require the co-factor, antithrombin III, for optimal anticoagulant activity. It has similar properties to hirudin, but does not elute with a protein peak upon Sephadex fractionation and has a slightly different molecular weight. Salivary gland homogenates contained neither a plasminogen activator nor fibrinolytic activity. The sera of rabbits used to maintain tsetses, which contained precipitating antibodies against saliva, did not neutralize the salivary anticoagulant in vitro. The properties of this anticoagulant suggest that it might be a potentially useful antithrombotic agent in man.
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PMID:Effects of tsetse (Glossina morsitans morsitans Westw.) (Diptera: Glossinidae) salivary gland homogenate on coagulation and fibrinolysis. 50 76

The fibrin-agar plate method was used to estimate fibrinolytic activity from the luminal surfaces of aorta and vena cava with or without denudation of endothelium in rabbits. Diffuse endothelial denudation was accomplished by air-dry injury to the luminal surfaces for 24 hours prior to sacrifice. The segments individually obtained from the aorta and vena cava were immediately turned inside out in a cylindrical fashion and soaked in a vial containing plasminogen-rich solution. The vials were kept in a refrigerator at 4 degrees C for 4 hours. Five microliter of the solution was dropped on a fibrin-agar plate containing 0.08% fibrinogen (plasminogen free) and 1.4% agar in 0.01 M phosphate buffer with a pH of 7.4. A thrombin solution was then added to the plates, which were incubated for 18 hours at 37 degrees C in a moist chamber. The fibrinolytically digested areas revealed no comparative difference in fibrinolytic activity between the aorta and the vena cava either in the experimental or control group. However, a plasminogen activator was detected on the luminal surfaces of both the aorta and the vena cava with endothelial denudation as well as in normal controls. These results suggest that luminal fibrinolytic activity may be located not only in endothelial cells but possibly in other sources as well. Further examination of the interaction between the tissue activator and the inhibitor and determination of their localization are needed. Thrombogenesis may be an important factor in atherogenesis; in certain circumstances, detachment of the endothelial cells exposes underlying collagen fibrils and subsequently initiates the aggregation of platelets and cellular proliferation in the intima. There are, however, many unresolved questions concerning the precise mechanisms of development, resolution and organization of thrombi.
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PMID:Measurement of endothelial fibrinolytic activity in aorta and vena cava in rabbits: a fibrin-agar plate method. 57 77

The Hageman factor dependent pathways are influenced by several control proteins which modulate the extent of activation and biologic activity of these enzyme substrates (Fig. 1). C1 INH plays a prominent role by acting at the common initiating step for all three Hageman factor dependent systems and its deficiency produces disease in man. Alpha-2 macroglobulin appears to play an important role in the fibrinolytic sequence, having potent activity towards both plasminogen activator and plasmin. Antithrombin most prominently influences the state of activation of the coagulation sequence by regulating the enzymatic activities of activated Factors XI, IX and X and, most importantly, that of thrombin. Significantly, deficiency of antithrombin results in increased thrombosis in man.
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PMID:Plasma inhibitors of the Hageman factor dependent pathways. 79 48

Two groups of specifically presensitized Macaca speciosa monkeys received renal allografts via anastomosis to an indwelling arteriovenous (A-V) shunt. One group was pretreated with heparin (2 mg/kg) intravenously and the other was also treated with constant heparin infusion (1 mg/kg/hr) directly into the renal artery. These studies were performed to evaluate the effects of heparin within the kidney on total and compartmental blood flow, complement (C3) levels, sequestration of formed elements, and activation of the coagulation, fibrinolytic, and kinin-forming systems during the initial 3 hours of hyperacute rejection. The results are compared with those previously reported in unmodified control allografts. Heparin prolonged blood clotting time to infinity, markedly prolonged total renal venous blood flow, and normalized compartmental distribution in both groups despite antibody deposition similar to that in controls. With heparin pretreatment only, initial morphologic injury was much reduced but then progressed rapidly. Marked initial cortical cyanosis with mottling appeared to change constantly and was associated with fluctuations in renal turgor, total blood flow, and sequestration of formed elements, all of which suggested repetitive local cortical arterial spasm and incremental destruction of the grafts. Activation of coagulation Factors II and XII was also revealed and marked net Factor VIII activity was observed in the venous effluent. The latter reflects either formation and release of this factor by the injured kidney, or provides in vivo documentation of the "hyperactivation" of Factor VIII by thrombin known to occur in vitro. The addition of intrarenal artery heparin infusion resulted in greater improvement in early total blood flow rates and more uniformly progressive cyanosis and loss of turgor, but the diffuse initial morphologic injury suggested more uniform perfusion of injured areas. Intrarenal consumption of C3 and sequestration of formed elements was similar to that in controls. Paradoxically, prompt activation and consumption of all coagulation factors, plasminogen, and prekallikrein were observed, but formed fibrin was sparse. The exess amount of Factor XIIa present during heparin blockade may have been diverted to production of plasminogen activator and kallikrein formation. The enormous numbers of neutrophils observed within vessels of grafts which showed the greatest kallikrein activation provide the probable in vivo demonstration of the chemotactic properties of kallikrein noted by others in vitro. Heparin-induced platelet aggregation may have played an important role in the failure of these grafts. These studies elucidate the intrarenal effects of heparin during hyperacute rejection and again suggest that vasoconstriction is the most important early determinant of graft failure, as blood flow appeared unrelated to the degree of vascular injury and apparent obstruction. Also, heparin may exer a beneficial effect on blood flow by other than its known action on coagulation.
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PMID:Hyperacute renal allograft rejection in the primate. Intrarenal effects of heparin and associated net release of factor VIII activity and kallikrein activation. 109 75


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