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)

Congenital dysfibrinogenaemia was found in three non-related patients. None of them had a haemorrhagic tendency, but one gave a thrombotic history. When their fibrinogens were treated with thrombin, they released fibrinopeptides A and B at normal rates, but the resultant fibrin monomers produced exhibited abnormal polymerization curves. This abnormality was more marked in fibrinogen Villajoyosa than in Barcelonas III and IV. Plasminogen and t-PA binding to fibrin monomers from the three dysfibrinogenaemias was similar to that of normal fibrin monomers. The gamma chain was purified from the three fibrinogens, treated with CNBr and the peptides produced were separated by reversed-phase HPLC. Chromatograms of digested fibrinogens showed an abnormal peak that was not present in the normal gamma chain. Amino acid sequence analysis of abnormal peptides and genomic DNA sequencing revealed that the gamma arginine 275 had been changed in the three fibrinogens; in two cases it was substituted by histidine, and in the third by cysteine. The altered properties observed in fibrin monomers produced from fibrinogen with the gamma Arg 275-->His or gamma Arg 275-->Cys substitution, suggests that this amino acid is important in maintaining the protein structure necessary for normal polymerization, but is not essential for the binding of t-PA or plasminogen to fibrin. It also suggests that the change Arg-->Cys produces more severe alterations in the functions of fibrinogen than the substitution Arg-->His.
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PMID:Abnormal polymerization and normal binding of plasminogen and t-PA in three new dysfibrinogenaemias: Barcelona III and IV (gamma Arg 275-->His) and Villajoyosa (gamma Arg 275-->Cys). 765 33

A mutant recombinant plasminogen activator inhibitor 1 (PAI-1) was created (Ser-338-->Cys) in which cysteine was placed at the P9 position of the reactive center loop. Labeling this mutant with N,N'-dimethyl-N-(acetyl)-N'-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) ethylene diamine (NBD) provided a molecule with a fluorescent probe at that position. The NBD-labeled mutant was almost as reactive as wild type but was considerably more stable. Complex formation with tissue or urokinase type plasminogen activator (tPA or uPA), and cleavage between P3 and P4 with a catalytic concentration of elastase, all resulted in identical 13-nm blue shifts of the peak fluorescence emission wavelength and 6.2-fold fluorescence enhancements. Formation of latent PAI showed the same 13-nm spectral shift with a 6.7-fold fluorescence emission increase, indicating that the NBD probe is in a slightly more hydrophobic milieu. These changes can be attributed to insertion of the reactive center loop into the beta sheet A of the inhibitor in a manner that exposes the NBD probe to a more hydrophobic milieu. The rate of loop insertion due to tPA complexation was followed using stopped flow fluorimetry. This rate showed a hyperbolic dependence on tPA concentration, with a half-saturation concentration of 0.96 microM and a maximum rate constant of 3.4 s-1. These results demonstrate experimentally that complexation with proteases is presumably associated with loop insertion. The identical fluorescence changes obtained with tPa.PAI-1 and uPA.PAI-1 complexes and elastase-cleaved PAI-1 strongly suggest that in the stable protease-PAI-1 complex the reactive center loop is cleaved and inserted into beta sheet A and that this process is central to the inhibition mechanism.
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PMID:A fluorescent probe study of plasminogen activator inhibitor-1. Evidence for reactive center loop insertion and its role in the inhibitory mechanism. 789 Jun 53

The developing neural retina expresses a set of extracellular proteases including plasminogen activator and gelatinases. Since neurites of retina cells cultured on fluorescent gelatin digest the substrate in their paths, we have suggested that the proteases are used by the tips of growing fibers to allow them to migrate within the mass of the tissue in vivo. In order to obtain further information about relationships between extracellular proteases and fiber growth, we have examined the effects of the specific inhibitors HS-LFA (HS-Leu-Phenylala-Ala, enantiomeric forms 1 and 2), bathophenanthroline sulfonate (BPS), phenylmethyl sulfonyl fluoride (PMSF), and relevant controls on the activity of retinal growth cones in vitro, monitored by time lapse video microscopy. Of the inhibitors tested, only the two enantiomeric forms of HS-LFA caused a reproducible cessation of both spike extension and filopodial processes at the growth cone ruffling, while control media had no effect. In some cases, the growth cone swelled and exhibited small protrusions. The behavior of growth cones was in sharp distinction to that of the cytoplasm of neural cells, and membrane ruffling of flat cells, which continued in activity throughout. Growth cone activity returned after several hours in the presence of the agent. BPS was toxic at concentrations above 2.5 mM. Below that, it had no effect. L-cysteine, PMSF, and control media had no effect. The relevance of these results to the possible role of proteases in fiber outgrowth from retinal cells is discussed.
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PMID:Inhibition of retinal growth cone activity by specific metalloproteinase inhibitors in vitro. 808 Oct 16

A comparative study of proteolytic enzymes and their inhibitors in three human leukemic lymphoid cell populations has been carried out. The lysates of all lymphoid cells contained cathepsins D, B, L and H as well as serine trypsin-like proteinases, several aminopeptidases, dipeptidyl aminopeptidase IV and plasminogen activator (urokinase type). The activities of individual proteinases and their ratios in all cell types under study varied essentially, suggesting that lymphoid cells with different functions have different sets of proteolytic enzymes. FPLC chromatography of the lysates revealed the presence of inhibitors of cysteine and serine trypsin-like proteinases. The procedure for isolation of cathepsins D, B, L and H and of their inhibitors has been proposed and partially purified protein preparations obtained. Some properties of cathepsins B and L and those of their inhibitor have been examined.
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PMID:[Proteolytic enzymes in human lymphocytic leukemia cells. II. Comparative characteristics of proteolytic enzymes and their inhibitors in three differing types of lymphoid cells]. 836 26

S-nitrosothiols may serve as carriers in the mechanism of action of endothelium-derived relaxing factor (EDRF) by stabilizing the labile nitric oxide (NO) radical from inactivation by reactive species in the physiological milieu and by delivering NO to the heme activator site of guanylyl cyclase. Low-molecular-weight thiols, such as cysteine and glutathione, form S-nitrosothiol adducts with vasodilatory and antiplatelet properties, and protein thiols can interact in the presence of NO and/or EDRF to form uniquely stable S-nitroso-proteins. We now show that the S-nitroso-proteins, S-nitroso-albumin, S-nitroso-tissue type plasminogen activator, and S-nitroso-cathepsin B, have potent antiplatelet effects with an IC50 of approximately 1.5 microM. In the dog, S-nitroso-albumin inhibits ex vivo platelet aggregation and significantly prolongs the template bleeding time from 2.15 +/- 0.13 (mean +/- SEM) to 9.70 +/- 1.24 minutes. The antiplatelet action of S-nitroso-proteins is associated with the stimulation of guanylyl cyclase and a significant decrease in fibrinogen binding to platelets. S-Nitroso-proteins undergo thiol-nitrosothiol exchange with low-molecular-weight thiols to form low-molecular-weight S-nitroso-thiols, and they also interact directly with the platelet surface, both of which processes facilitate generation of NO. These data suggest that S-nitroso-proteins are potent antiplatelet agents and may be intermediates in the antiplatelet mechanism of EDRF action.
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PMID:Antiplatelet properties of protein S-nitrosothiols derived from nitric oxide and endothelium-derived relaxing factor. 838 13

A series of N-peptidyl-O-acyl hydroxamates with a lysine in P1 was synthesized and tested as inactivators of lysosomal cysteine proteinases (cathepsins S, L, B and H) and trypsin-like serine proteinases (trypsin, thrombin, plasmin, t-PA). N-peptidyl-O-acyl hydroxamates were shown to be selective inhibitors of cysteine proteinases. With the exception of cathepsin H, the lysosomal cysteine proteinases were inactivated 2-5 orders of magnitude more rapidly than serine proteinases with a comparable primary substrate specificity. The highest second-order rate constants of inactivation for the cysteine proteinases are in the range of 10(5)-10(6) M-1 s-1. The order of inhibitor specificity for the cysteine proteinases is comparable to the enzyme's substrate specificity.
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PMID:Novel N-peptidyl-O-acyl hydroxamates: selective inhibitors of cysteine proteinases. 839 90

The myxoma and malignant rabbit fibroma poxviruses are lethal tumorigenic viruses of rabbits whose virulence is modulated by the production of a virus-encoded secreted serine proteinase inhibitor, SERP-1. This viral protein was detected in medium harvested from myxoma and malignant rabbit fibroma virus-infected cells, and its inhibitory profile has been characterized by gel and kinetic analysis. SERP-1 forms complexes with and inhibits the human fibrinolytic enzymes plasmin, urokinase, and two-chain tissue-type plasminogen activator (association rate constants 3.4 x 10(4), 4.3 x 10(4), and 3.6 x 10(4) M-1 s-1 respectively). It is also able to inhibit C1S, the first enzyme in the complement cascade with an association rate constant which was unaffected by the addition of heparin (1.3 x 10(3) M-1 s-1). SERP-1 acts as a substrate for and is cleaved by thrombin, porcine trypsin, human neutrophil elastase, porcine pancreatic elastase, thermolysin, subtilisin, bovine alpha-chymotrypsin, and factor Xa. Incubation with kallikrein and cathepsin G had no effect. The structure of SERP-1 has been modeled on other members of the serpin family which revealed the characteristic serpin architecture apart from the absence of the D-helix. Structural analysis and kinetic assays demonstrate that the absence of this region does not prevent inhibitory activity and furthermore allow the identification of cysteine residues involved in internal and intermolecular disulfide bonding.
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PMID:Inhibition of plasmin, urokinase, tissue plasminogen activator, and C1S by a myxoma virus serine proteinase inhibitor. 841 56

Human cytosolic phospholipase A2 (cPLA2) is an arachidonic acid specific enzyme which may play a role in arachidonic acid release, eicosanoid production, and signal transduction. The PLA2 activity of this enzyme is stimulated by microM levels of Ca2+. Using a pure recombinant enzyme, we have confirmed that cPLA2 is not absolutely dependent on Ca2+, since Sr2+, Ba2+ and Mn2+ also gave full enzyme activity. Heavy metals, in contrast, inhibited enzyme catalysis suggesting the involvement of an essential cysteine residue. In the absence of Ca2+, high salt concentrations overcame the requirement for divalent metals, indicating that Ca2+ is not required for PLA2 catalytic activity. cPLA2 also displays a lysophospholipase (lyso PLA) activity with lysophosphatidylcholine micelles as a substrate. Unlike the PLA2 activity, the lyso PLA activity toward these micelles is not stimulated by Ca2+. However, upon the addition of glycerol or Triton X-100 to the assay, Ca2+ activation is observed, indicating that substrate presentation can affect the apparent Ca2+ dependence. Glycerol was found to be a potent stimulator of lyso PLA activity and specific activities up to 50 mumol min-1 mg-1 were observed. In addition to the PLA2 and lyso PLA activities, we report that cPLA2 displays a relatively low, CoA-independent transacylase activity which produces phosphatidylcholine from lysophosphatidylcholine substrate. The observation of this novel transacylase activity is consistent with the formation of an acyl-enzyme intermediate.
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PMID:Metal ion and salt effects on the phospholipase A2, lysophospholipase, and transacylase activities of human cytosolic phospholipase A2. 848 88

G4120, L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-alpha- aspartyl-cyclic(1-->5)-sulfide, 5-oxide, a synthetic cyclic Arg-Gly-Asp-containing pentapeptide, has a high affinity (dissociation constant of 4 nM) for the platelet glycoprotein (GP) IIb/IIIa receptor. The effects of its intravenous or endobronchial administration on thrombolysis, reocclusion, and bleeding time prolongation induced with 0.45 mg/kg bolus injections of recombinant tissue-type plasminogen activator in combination with intravenous heparin (4,000-unit bolus and 1,000 units each hour) were studied in a canine model consisting of an erythrocyte-rich blood clot in the left anterior descending coronary artery. Coronary patency was monitored for 3 hours both by ultrasonic flow probe and by repeat coronary angiography. Four groups of six to 10 dogs were studied with intravenous infusions of 0, 0.1, 0.2, or 0.3 mg/kg G4120 over 60 minutes. G4120 at a dose of 0.3 mg/kg reduced the time to reflow from a mean control value of 45 to 8 minutes (p = 0.036) and delayed reocclusion (p = 0.001). Four groups of five or six dogs were studied with endobronchial instillation of G4120 in a randomized, blinded study design using 0, 0.13, 0.25, or 0.5 mg/kg G4120. Endobronchial G4120 at a dose of 0.5 mg/kg reduced the time to reflow from a mean control value of 52 to 7 minutes (p = 0.039) and abolished cyclic reocclusion and reflow (p = 0.008). G4120 induced a dose-related transient prolongation of the template bleeding time and inhibition of ADP-induced platelet aggregation. G4120, a synthetic low-molecular-weight GPIIb/IIIa inhibitor that may be produced by chemical synthesis, may be of clinical value as a conjunctive agent for thrombolysis in patients with ischemic coronary syndromes.
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PMID:Intravenous and endobronchial administration of G4120, a cyclic Arg-Gly-Asp-containing platelet GPIIb/IIIa receptor-blocking pentapeptide, enhances and sustains coronary arterial thrombolysis with rt-PA in a canine preparation. 848 25

Extravasation and intravasation of tumor cells in solid malignant tumors is controlled by 3 steps: 1) attachment to and interaction of tumor cells with components of the basement membrane and the extracellular matrix, 2) local proteolysis, and 3) tumor cell migration. Evidence has accumulated that different types of tumor-associated proteases, their inhibitors and receptors are involved in tumor invasion and metastasis. Four different classes of proteases are known to be correlated with the malignant phenotype: 1) Matrix metalloproteases; including collagenases, gelatinases and stromelysins. 2) Cysteine proteases; including cathepsins B and L. 3) Aspartyl protease cathepsin D. 4) Serine proteases; including plasmin and tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). A strong independent prognostic value (relapse-free and/or overall survival) has especially been demonstrated for uPA and its inhibitor PAI-1 in patients with cancer of the breast, ovary, stomach, esophagus, colon, lung, and kidney thus predicting the course of the cancer disease. The strong correlation between elevated uPA and/or PAI-1 values in primary cancer tissues and the malignant phenotype of cancer cells has prompted to explore new tumor biology-oriented concepts in order to suppress uPA or uPA receptor (CD87) expression or to abrogate interaction of uPA with CD87. Various very different approaches to interfere with the expression or reactivity of uPA or CD87 at the gene or protein level were successfully tested including antisense oligonucleotides, antibodies, inhibitors and recombinant or synthetic uPA and CD87 analogues.
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PMID:Urokinase-type plasminogen activator (uPA) and its receptor (CD87): a new target in tumor invasion and metastasis. 855 77


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