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)

Previous studies have established that plasma cryoprecipitates of tumor patients, culture media of transformed cells and defined proteolytic fragments of fibronectin enhance the morphological cell transformation ( TEF activity) in cultures of chicken embryo fibroblasts infected with temperature-sensitive mutants of Rous sarcoma virus. We now report that purified human tissue type plasminogen activator (t-PA), but not urokinase (u-PA), has a similar TEF activity, at doses as low as 2 ng/ml (30 pM). Specific antibodies effectively neutralized the activity. No significant contamination (less than or equal to 1%) between the preparations of t-PA and fibronectin (FN) or its fragments ( FNdp ) was detected. The results suggest that t-PA may have a direct role in the process of morphological cell transformation in vitro.
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PMID:Tissue type plasminogen activator, but not urokinase, exerts transformation-enhancing activity. 653 4

We report the isolation of a specific protease zymogen from chicken plasma. The purification procedure involves barium citrate precipitation, ammonium sulfate fractionation, removal of plasminogen and plasmin on lysine-Sepharose, followed by anion and cation exchange, and gel permeation chromatography. Based on quantitative radioimmunoassay the zymogen is present in plasma at a concentration of 160 mg/liter, and it is obtained by our procedure in highly purified form with a yield of 1.4%. The single polypeptide chain contains an NH2-terminal alanine residue. The native molecule migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 84,000 under reducing conditions. It can be identified as an inactive proenzyme because it has very low amidolytic activity, does not react with the fluorescent active site titrant 4-methyl-lumbelliferyl p-guanidinobenzoate, and does not incorporate radioactive [3H]diisopropylfluorophosphate. It is very susceptible to limited proteolysis which converts it to an active enzyme with trypsin-like specificity. The active enzyme, likewise a single polypeptide chain, migrates as a doublet with apparent molecular weights of 39,000 and 40,000. Its amidolytic activity with synthetic peptide substrates is at least 40-fold higher than that of the proenzyme, it reacts efficiently with 4-methylumbelliferyl p-guanidinobenzoate, and incorporates [3H]diisopropylfluorophosphate while undergoing irreversible inactivation. The enzyme appears to be a reasonably efficient plasminogen activator in zymographic gels, but not in solution. With human high molecular weight kininogen as substrate the enzyme was about 25% as efficient as human plasma kallikrein. It lacks any plasminogen-independent proteolytic activity with other protein substrates, and it hydrolyzes small peptide substrates designed for both human kallikrein and urinary urokinase, respectively. Inhibition studies with peptide chloromethyl ketones indicate enzymatic properties closer to human plasma kallikrein than to the human plasminogen activator urokinase (EC 3.4.21.31). The chicken plasma enzyme and the plasminogen activator from the conditioned media of Rous sarcoma virus-transformed chick embryo fibroblasts treated with tumor promoter are different by criteria of tryptic peptide maps, and amino acid composition and enzymatic specificity. The designations chicken plasma prekallikrein plasminogen proactivator and chicken plasma kallikrein plasminogen activator are proposed for the zymogen and enzyme forms, respectively. Using rabbit antibodies against the proenzyme we developed a solid phase immunoadsorption procedure that allowed us to isolate the protein with an overall yield of 11.4%.
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PMID:A proenzyme from chicken plasma similar to human plasma prekallikrein. 655 13

The antifibrinolytic activity of cytosols obtained from cultured rabbit endothelial cells was studied to determine whether it resulted from the presence of an antiplasmin or an antiactivator. These cytosol preparations inhibited the fibrinolytic activity initiated by some plasminogen activators (e.g. urokinase, rabbit endothelial cell activator), but not others (e.g. activators associated with bovine endothelial cells and Rous sarcoma virus-infected chick embryo fibroblasts), suggesting that inhibition occurred at the level of plasmin formation, not plasmin activity. The fibrinolytic activity of plasmin itself was unaffected by concentrations of cytosol that completely blocked urokinase-mediated fibrinolysis consistent with this conclusion. In addition, the ability of urokinase to cleave 125I-plasminogen into its characteristic activation fragments was inhibited by cytosol in a dose-dependent manner. When urokinase was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, two peaks of activity were detected, corresponding to Mr = 55,000 and 32,000. Urokinase preincubated with cytosol and analyzed in a similar manner demonstrated no activity in any portion of the gel, suggesting that its ability to function as a plasminogen activator was irreversibly lost following its interaction with cytosol. These results indicate that the antifibrinolytic activity of rabbit endothelial cells results from the presence of a molecule or molecules with antiactivator activity. The cellular location and unusual degree of specificity distinguish the endothelial cell inhibitor(s) from antifibrinolytic agents observed in other cells and in plasma and platelets.
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PMID:An inhibitor of plasminogen activator in rabbit endothelial cells. 678 54

We have isolated a novel isoform of phospholipase A(2). This enzyme was designated srPLA(2) because it was discovered while analyzing the proteins interacting with different forms of the v-Src oncoproteins isolated from Rous sarcoma virus-transformed hamster cells. It contains all the functional regions of the PLA(2) group IIA proteins but differs at its C-terminal end where there is an additional stretch of 8 amino acids. The SrPLA(2) isoform was detected as a 17-kDa precursor in cells and as a mature 14-kDa form secreted in culture medium. A direct interaction of the 17-kDa precursor with the Src protein was observed in lysates of transformed cells. Both the 17- and 14-kDa forms were found to be phosphorylated on tyrosine. To our knowledge, this is the first report of a PLA(2) group II protein that is tyrosine phosphorylated. We surmise that srPLA(2) interacts with the Src protein at the cell membrane during the process of its maturation.
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PMID:A novel group IIA phospholipase A2 interacts with v-Src oncoprotein from RSV-transformed hamster cells. 1142 22

A great deal of evidence has accumulated in recent years for an important but complex role for proteases in tumor development. However, attempts to treat cancer in humans with anti-proteases have been disappointing, and it has been suggested that more basic groundwork is needed before anti-proteases can be effectively applied. Considerable basic information comes from the recognition that earlier results on transformation of chicken embryo fibroblasts (CEF) by the Bryan strain of Rous sarcoma virus (B-RSV) can be explained in terms of proteases and their inhibitors. In particular, the full but reversible normalization of discrete transformed foci by appropriate concentrations of fetal bovine or of calf serum implies a causal role for multiple proteases in transformation, and the efficacy of treatment with a physiological balance of their natural inhibitors. Addition of certain proteases to contact-inhibited normal cultures was then found to stimulate their proliferation. The toxicity of medium produced by CEF heavily transformed with B-RSV suggests that cachexia and other systemic effects of human cancer may result from vascular dissemination of peptides from pericellular proteolysis within tumors. Comprehensive studies revealed significant increases of plasminogen activator and matrix metalloproteinases (MMPs) after infection of CEF with other strains of RSV, and correlation of the proteases with aspects of transformation. A similar role for proteases is indicated in the transformation of mammalian cells by chemical and physical agents. The information gained from functional experiments on cell transformation in culture is complementary to that obtained from the molecular identification of proteases and their inhibitors in all stages of tumor development. The speed, quantification and easy manipulation of the RSV-CEF transformation assay can be combined with current methods of characterizing proteases and anti-proteases to further enrich our basic knowledge of neoplastic development in cells, and facilitate its application to the treatment of cancer.
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PMID:Complementary approaches to understanding the role of proteases and their natural inhibitors in neoplastic development: retrospect and prospect. 1277 Oct 23


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