Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect was examined of individual caseins on the rate of plasminogen activation by bovine urokinase-type and tissue-type plasminogen activators. All individual caseins (alpha-CN, beta-CN, and kappa-CN) enhanced the activity of both types of plasminogen activators. Optimal concentrations for alpha-CN and beta-CN were 5 and 25 micrograms/ml, respectively. The enhancement of enzymatic activity declined when concentrations of alpha-CN and beta-CN were higher. In contrast, increasing concentrations of kappa-CN from 0 to 200 micrograms/ml resulted in corresponding increases in activity of both types of plasminogen activators. On a weight basis, alpha-CN was the most effective enhancer of plasminogen activator activity. Indirect evidence obtained with experiments utilizing alpha-CN immobilized on agarose suggested that the effect is related to extensive binding of plasminogen and both types of plasminogen activators to casein.
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PMID:Effect of individual caseins on plasminogen activation by bovine urokinase-type and tissue-type plasminogen activators. 778 5

Snake venoms, especially from the Crotalidae family, contain a variety of enzymes that prevent blood coagulation by virtue of their fibrinolytic enzymes. Nineteen snake venoms were screened for fibrinolytic activity and the highest activity was found in the venom of Crotalus basiliscus basiliscus venom. The active principle, basilase, was isolated, purified, and found to have fibrinolytic and fibrinogenolytic activity. It had a molecular weight of 22,000 and 1 mol of zinc per mole of protein associated with it. The proteolytic activity of the enzyme against dimethyl casein was inhibited by ethylenediaminetetraacetic acid and alpha 2-macroglobulin. It did not inactivate alpha 2-macroglobulin. Basilase did not have any of the following activities: thrombin-like, factor X-like, protein C activating, or urokinase-like. It caused neither hemorrhage nor platelet aggregation. In spite of its proteolytic activity, basilase did not hydrolyze the membranes of platelets. Basilase had 24% alpha-helix, 31% beta-sheet, 25% turns, and 20% unordered structure, as determined by Fourier Transform Infrared spectroscopy. Basilase is an enzyme that hydrolyzes fibrin directly without activation of plasminogen.
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PMID:Biochemical characterization of basilase, a fibrinolytic enzyme from Crotalus basiliscus basiliscus. 789 51

Clots formed from platelet rich plasma were found to be lysed more readily by low concentrations of pro-urokinase (pro-UK) than clots formed from platelet poor plasma. This was not a non-specific effect since the reverse occurred with tissue plasminogen activator. A mechanical explanation due to platelet-mediated clot retraction was excluded by experiments in which retraction was inhibited with cytochalasin B. Therefore, a platelet-mediated enzymatic mechanism was postulated to explain the promotion of fibrinolysis. Casein autography of isolated platelets revealed a approximately 90 kDa band of activity which comigrated with plasma prekallikrein (PK)/kallikrein, a known activator of pro-UK. Furthermore, treatment of platelets with plasma PK activator (PPA), consisting essentially of factor XIIa, induced activation of pro-UK and of chromogenic substrate for kallikrein (S-2302). This activity corresponded to approximately 40-200 pM kallikrein per 10(8) washed and gel filtered platelets per ml. The activation of pro-UK by PPA-pretreated platelets was dose-dependent and inhibited by soybean trypsin inhibitor but not by bdellin, a specific inhibitor of plasmin, nor by the corn inhibitor of factor XIIa. Kinetic analysis of pro-UK activation by kallikrein showed promotion of the reaction by platelets. The KM of the reaction was reduced by platelets by approximately 7-fold, while the kcat was essentially unchanged. In conclusion, PK was shown to be tightly associated with platelets where it can be activated by factor XIIa during clotting. The activation of pro-UK by platelet-bound kallikrein provides an explanation for the observed platelet mediated promotion of pro-UK-induced clot lysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Platelet-bound prekallikrein promotes pro-urokinase-induced clot lysis: a mechanism for targeting the factor XII dependent intrinsic pathway of fibrinolysis. 802

Neonatal human foreskin obtained at circumcision was cut into 2 x 2-mm pieces and placed in organ culture. Culture medium consisted of a serum-free, growth factor-free basal medium containing either 0.15 mmol/L Ca2+ or 1.4 mmol/L Ca2+. Some cultures were left as control, whereas others were treated with 3 mumol/L all-trans retinoic acid (RA). In the presence of RA, epidermal cohesion was disrupted and the upper layers separated from the viable epidermis beneath. This effect was observed under both low Ca2+ and high Ca2+ conditions. At 2-day intervals, culture fluids were collected and analyzed for serine and metalloproteinase activities. Serine proteinase activity was detected in the culture fluids and virtually all of the detected activity was dependent on the presence of plasminogen. Activity was elevated in the RA-treated tissues and this was due to increased amounts of both urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA). Elastase and cathepsin G were not detected in either control or RA-treated cultures. Increased plasminogen activator levels were also detected in RA-treated keratinocytes and fibroblasts in monolayer culture. Significant amounts of t-PA (though not u-PA) were found in fibroblast culture fluids, whereas both t-PA and u-PA were detected in culture fluids from keratinocytes. Metalloproteinase activity was also detected in the culture fluids of control and RA-treated tissues but in contrast to plasminogen activator, metalloproteinase activity decreased in the presence of RA. Casein and gelatin zymographic studies indicated the presence of both 92- and 72-kd gelatinases and stromelysin-1 and suggested that the decreased activity was primarily due to reduction in the 92- and 72-kd gelatinases. When serine proteinase inhibitors (aprotinin and soybean trypsin inhibitor) were included in the culture medium throughout the incubation period, epidermal discohesion was reduced. A metalloproteinase inhibitor, tissue inhibitor of metalloproteinase-2, did not have this effect. Taken together, these data show that a number of proteolytic enzymes are produced during organ culture of human skin. They suggest that these proteases may influence the structural integrity of the tissue.
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PMID:Expression of serine proteinases and metalloproteinases in organ-cultured human skin. Altered levels in the presence of retinoic acid and possible relationship to retinoid-induced loss of epidermal cohesion. 808 40

The enzymatic activities of uPA, and a collagenase-like proteinase in the post-nuclear fraction of cell homogenates of a metastatic carcinomatous cell line following X-ray irradiation were examined by the use of chromogenic substrates and by casein- or gelatin-containing zymographies and electrophoretic gel stained with avidin-conjugated peroxidase. Enhanced activities were observed in these cells, while those of 5'nucleotidase and Na(+)-K(+)-ATPase were attenuated. A partial purification and characterization of the collagenase showed that it was able to hydrolyze the heat-denatured type-I collagen more efficiently than the native one. The activation of both uPA and collagenase enables an efficient degradation of matrix barrier proteins. These findings suggest that following a certain dose range of X-ray irradiation, tumor cells may increase their ability to migrate and invade through the enhancement of uPA and collagenase activities.
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PMID:The concomitant augmentation of urokinase-type plasminogen activator and collagenase-like proteinase activities in X-ray irradiated cells of a human metastatic carcinomatous line. 809

The plasminogen activators, tissue type and urokinase type (tPA and uPA, respectively) have been identified in human skin under normal conditions and in various inflammatory dermatoses, including psoriasis. By Northern blot analyses, mRNA for uPA, but not for tPA, has been previously identified in epidermal extracts from normal skin, whereas in psoriasis, mRNA for tPA is readily detected. To further characterize uPA and tPA expression in psoriasis, the localization of uPA and tPA mRNAs was evaluated by in situ hybridization. Studies were conducted using lesional and nonlesional skin of patients with psoriasis as well as normal skin. Additionally, in situ zymography using casein gel overlays was utilized to assess enzymatic activity. In psoriatic lesional skin, both uPA and tPA mRNAs were demonstrated by in situ hybridization. Message for tPA was observed throughout the epidermis with areas of accentuation in the superficial stratum spinosum. Message for uPA was more focal and was localized primarily in the basal layer. Zymography showed tPA activity was coordinately increased in psoriatic lesions. Uninvolved skin of psoriatic patients was similar to that of normal skin with respect to expression of plasminogen activators. In normal epidermis, neither tPA nor uPA mRNA could be detected by in situ hybridization. Activity for uPA, but not tPA, was observed by zymography. These studies suggest that alterations in plasminogen activators expression may contribute to the pathogenesis of psoriasis.
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PMID:Expression of plasminogen activator enzymes in psoriatic epidermis. 812 Apr 16

We have analyzed the occurrence of components of the plasminogen activation system in bovine milk. Zymographic analyses showed that tissue-type plasminogen activator (t-PA) occurred in association with casein micelles, partially as a complex with type-1 plasminogen activator inhibitor (PAI-1), whereas urokinase-type plasminogen activator (u-PA) was confined to milk leukocytes. Whey contained a component with a plasminogen dependent proteolytic activity which was shown to be plasma prekallikrein (PPK). The u-PA in the milk leukocytes was shown to be bound to urokinase receptor (u-PAR). A purification to near-homogeneity of the bovine u-PAR was undertaken. Investigating the novel t-PA binding to casein micelles by ligand blotting and Sepharose immobilized casein, multimeric forms of kappa-casein and dimeric alpha s2-casein were identified as t-PA binding components. The kappa-casein gene and the fibrinogen gene are believed to have evolved from a common ancestor. Thus, the recent finding that casein enhances t-PA catalyzed plasminogen activation (Marcus, G., Hitt, S., Harvey, S.R. and Tritsch, G.L. (1993) Fibrinolysis 7, 229-236), and the observed t-PA/casein binding suggests that the casein micelle, which also contains plasminogen, may serve as a matrix for t-PA-catalyzed plasminogen activation in milk.
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PMID:The plasminogen activation system in bovine milk: differential localization of tissue-type plasminogen activator and urokinase in milk fractions is caused by binding to casein and urokinase receptor. 818 64

In the course of analysis of plasminogen in microglial conditioned medium (Mic-CM), novel low-molecular-weight (LMW) zymogen with a molecular mass of approximately 36 kDa was detected by casein-urokinase zymography. Because this form was produced when rat native plasminogen was incubated with Mic-CM, a specific protease in the Mic-CM was thought to be responsible for the production of LMW plasminogen. The production of LMW plasminogen was strongly inhibited by elastase inhibitors. Furthermore, elastase (pancreatic or leukocyte) was also found to produce LMW zymogen from native plasminogen. These results indicate that LMW plasminogen is produced through limited proteolysis by an elastase-like protease in Mic-CM. To determine the biochemical characteristics of LMW plasminogen, rat native plasminogen was cleaved by pancreatic elastase, and the fragments (LMW plasminogen and nonzymogen fragments) were purified by several kinds of column chromatography. Amino acid sequence analysis revealed that LMW plasminogen is a carboxy-terminal region that contains the fifth kringle domain and a protease active site, and the amino acid sequence is identical to that of LMW plasminogen produced by Mic-CM. On the other hand, the nonzymogen fragment was the amino-terminal region containing four kringle domains. The effects of native plasminogen and the fragments on neurite outgrowth of rat brain explant were examined. LMW plasminogen promoted neurite outgrowth as well as did native plasminogen, whereas nonzymogen fragments did not. These results suggest that LMW plasminogen, which is produced from native plasminogen by elastase, may be a physiologically active molecule that mediates the intercellular interaction between microglia and neurons.
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PMID:Microglia-derived elastase produces a low-molecular-weight plasminogen that enhances neurite outgrowth in rat neocortical explant cultures. 824 67

The contact-dependent intrinsic pathway of fibrinolysis involving factor XII, prekallikrein (PK) and pro-urokinase (pro-UK) remains poorly understood. Casein autography of washed, intact platelets revealed both PK and pro-UK. Accordingly, platelets may mediate physiological thrombolysis by this pathway since factor XIIa activates PK and kallikrein activates pro-UK. Acid washing dissociated PK but not pro-UK from platelets. Exogenous pro-UK was specifically incorporated by platelets from the ambient fluid and similarly could not be dissociated from intact platelets. Therefore, platelets may also mediate an effect from therapeutically administered pro-UK by prolonging its half-life.
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PMID:Pro-urokinase and prekallikrein are both associated with platelets. Implications for the intrinsic pathway of fibrinolysis and for therapeutic thrombolysis. 844 Mar 90

The expression of plasminogen activators and inhibitors was examined in denuded arteries. Within 5 days, smooth muscle cells (SMCs) on the luminal surface expressed the mRNA for tissue-type plasminogen activator (TPA), urokinase type plasminogen (UPA), the receptor for UPA (UPAR), and plasminogen activator inhibitor type-1 (PAI-1). Similar results were seen after 8 days. Six weeks later, only TPA mRNA was still expressed by SMCs on the luminal surface. En face casein zymograms revealed a net fibrinolytic activity in areas covered with luminal SMCs. Reverse zymography showed no antifibrinolytic activity in these zones. Quiescent endothelial cells did not express TPA, UPA, UPAR, or PAI-1 mRNA. Regenerating endothelium at the wound edge strongly expressed TPA. UPA, and UPAR, as well as PAI-1. UPA and UPAR expression was highly restricted to cells at the wound edge and was not present elsewhere. En face zymography showed no plasmin activity in endothelialized areas, and reverse zymography showed a net fibrinolytic activity in endothelialized zones. These results suggest that plasminogen activator and inhibitor expression correlates with the migration of both SMCs and endothelial cells into an arterial wound.
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PMID:Migration of arterial wall cells. Expression of plasminogen activators and inhibitors in injured rat arteries. 859 99


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