Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The capacity of cells to interact with the plasminogen activator, urokinase, and the zymogen, plasminogen, was assessed using the promyeloid leukemic U937 cell line and the diploid fetal lung GM1380 fibroblast cell line. Urokinase bound to both cell lines in a time-dependent, specific, and saturable manner (Kd = 0.8-2.0 nM). An active catalytic site was not required for urokinase binding to the cells, and 55,000-mol-wt urokinase was selectively recognized. Plasminogen also bound to the two cell lines in a specific and saturable manner. This interaction occurred with a Kd of 0.8-0.9 microM and was of very high capacity (1.6-3.1 X 10(7) molecules bound/cell). The interaction of plasminogen with both cell types was partially sensitive to trypsinization of the cells and required an unoccupied high affinity lysine-binding site in the ligand. When plasminogen was added to the GM1380 cells, a line with high intrinsic plasminogen activator activity, the bound ligand was comprised of both plasminogen and plasmin. Urokinase, in catalytically active or inactive form, enhanced plasminogen binding to the two cell lines by 1.4-3.3-fold. Plasmin was the predominant form of the bound ligand when active urokinase was added, and preformed plasmin can also bind directly to the cells. Plasmin on the cell surface was also protected from its primary inhibitor, alpha 2-antiplasmin. These results indicate that the two cell lines possess specific binding sites for plasminogen and urokinase, and a family of widely distributed cellular receptors for these components may be considered. Endogenous or exogenous plasminogen activators can generate plasmin on cell surfaces, and such activation may provide a mechanism for arming cell surfaces with the broad proteolytic activity of this enzyme.
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PMID:The plasminogen system and cell surfaces: evidence for plasminogen and urokinase receptors on the same cell type. 302

Human plasma alpha(2)-macroglobulin is an inhibitor of circulating proteases that function in hemostatic and inflammatory reactions but the biochemical nature of its interaction with these enzymes is not well defined. This investigation has found that alpha(2)-macroglobulin is comprised of subunit chains of 185,000 molecular weight as analyzed by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate. Trypsin, thrombin, plasmin, and plasma kallikrein in amounts completely bound to alpha(2)-macroglobulin attacked one region in the subunit chain producing a single derivative with a molecular weight of 85,000 indicating that hydrolysis occurred at or near the center of the parent chain. The proteolytic derivative was also identified in an alpha(2)-macroglobulin preparation from plasma incubated with the plasminogen activator, urokinase. alpha(2)-macroglobulin functionally capable of binding enzyme appeared to be required both for limiting tryptic hydrolysis and for confining the concentration dependent increase in the derivative chain to the 1st min of incubation since acid-denatured alpha(2)-macroglobulin that failed to bind trypsin was extensively degraded. Three derivative chains resulted from the interaction of alpha(2)-macroglobulin with chymotrypsin demonstrating the presence of at least two chymotrypsin susceptible regions in the precursor chain. Reduction of the alpha(2)-macroglobulin-enzyme mixture was required for the identification of the derivative subunit chains establishing that these cleavage products were covalently linked to the parent molecule by disulfide bridges. Thus, alpha(2)-inacroglobulin acts as a substrate for circulating proteases, a finding which may also pertain to the mechanism of action of other plasma enzyme inhibitors.
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PMID:Studies on human plasma alpha 2-macroglobulin-enzyme interactions. Evidence for proteolytic modification of the subunit chain structure. 426 59

The urinary type plasminogen activator, urokinase (uPA) is localized on the cell surface through the binding of a specific receptor, the uPA receptor (uPAR). The uPA localization enhances plasmin formation on the cell surface and facilitates cell migration. The cellular and tissue distribution of uPAR is not fully established. We have analyzed uPAR expression in nine leukemic cell lines of distinct lineages and maturational states and correlated this with expression of plasminogen receptors, tissue-type plasminogen activator (tPA) receptors and LDL receptor-related protein (LRP). The most immature and least differentiated cell line (an erythro-myeloid cell line) and cells of lymphoid lineage, did not express uPAR, whereas cells differentiated along the myelo-monocytic pathway displayed this receptor. Plasminogen and tPA receptors were expressed by all leukemic cell lines and by all nucleated peripheral blood cells but B and T lymphocytes were negative for cell surface expression of both uPAR and LRP while monocytes and neutrophils were positive for expression of both uPAR and LRP. PMA stimulation induced surface expression of uPAR in lymphocytes but did not induce expression of LRP by these cells. In contrast, lymphoid cell lines were negative for uPAR expression even after PMA stimulation, indicating differences in regulation of uPAR expression between lymphocytes and lymphoid cell lines. The pattern of uPAR expression on leukemic cell lines was also studied on bone marrow blast cells from leukemic patients. Only the most mature myeloid cells expressed uPAR on their surfaces. In contrast, M3 leukemic cells and other blast cells displaying lymphoid markers such as TdT (+) and/or CD2 (+) did not express intracellular or cell-surface associated uPAR, indicating an heterogeneity among these promyelocytic cells and suggesting that uPAR may be a useful marker for leukemia typing. Myeloid blast cells from some patients contained intracellular pools of uPAR but displayed no receptor on the cell surface, suggesting that translocation may be a mechanism regulating uPAR expression in these cells. The comparison of uPAR expression between these cell lines and peripheral blood cells and it correlation with plasminogen receptors, tPA receptors and LRP expression offers new insights regarding potential mechanisms for regulation of uPA-uPAR-mediated pericellular proteolysis.
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PMID:Distinct patterns of urokinase receptor (uPAR) expression by leukemic cells and peripheral blood cells. 897 26

Rat proximal tubular epithelial cells derived from Wistar-Kyoto and spontaneously hypertensive rats were grown to confluency on semipermeable tissue culture inserts, and the plasminogen system of these cells was analyzed using enzyme assays, Western analysis, zymography, and reverse transcriptase-polymerase chain reaction. The tubular epithelial cells are capable of activating exogenous plasminogen to plasmin by endogenous plasminogen activators. The cells produce tissue-plasminogen activator, urokinase-plasminogen activator, plasminogen activator inhibitor-1, and urokinase-plasminogen activator receptor. These cells also produce the Heymann nephritis autoantigen, gp330 (megalin), and an associated protein of 45 kd (RAP). Incubation with transforming growth factor-beta 1 resulted in a decrease in plasminogen activation, primarily because of an increase in plasminogen activator inhibitor-1 RNA and protein and a decrease in u-PA RNA as noted by quantitative reverse transcriptase-polymerase chain reaction, Western analysis, and zymography. Incubation of these cells with tumor necrosis factor-alpha resulted in an increase in plasminogen activating ability, presumably through an increase in urokinase. Gp330 and the associated 45-kd protein (RAP) RNA were decreased in cells treated with tumor necrosis factor-alpha. The data presented indicates that these transformed proximal tubular epithelial cells may be used to study changes that may occur during Heymann nephritis with respect to the plasminogen system and the autoantigen gp330.
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PMID:Effect of TGF-beta 1 and TNF-alpha on the plasminogen system of rat proximal tubular epithelial cells. 904 36

Fibrinolytic enzyme inhibitors hamper the determination of the specific fibrinolytic serine protease activity. Reportedly, chemical anti-inhibitors eliminate the influence of fibrinolytic inhibitors, but it remains unclear to what extent they change the specific activity of fibrinolytic serine proteases. We studied the influence of chemical anti-inhibitors (chloramine T, flufenamate, sodium lauryl sulfate, and methylamine) on fibrinolytic serine proteases and fibrinolytic enzyme inhibitors using the physiological substrate fibrin as plasmin substrate. Low concentrations of chloramine T (0.01 mmol/l) prevent the inhibition of plasminogen activators. Higher concentrations (1 mmol/l) reduce the inhibition of plasmin, but simultaneously quench the plasminogen activator activity. Flufenamate eliminates most fibrinolytic enzyme inhibitors, but increases the activity of plasmin (apparent recovery 140%) and plasminogen activators (apparent recovery > 200%). Sodium lauryl sulfate eliminates the major fibrinolytic enzyme inhibitors, but increases the activity of plasmin (apparent recovery > 200%) and plasminogen activator, urokinase type (apparent recovery 130%). Methylamine affects only plasmin inhibition. We conclude that chemical anti-inhibitors may invalidate the analytical specificity of methods for the determination of fibrinolytic serine protease activity.
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PMID:The effect of chemical anti-inhibitors on fibrinolytic enzymes and inhibitors. 918 4