Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Plasmin was recently reported to inhibit platelet aggregation. We report here on the interaction of plasmin with the adenylate cyclase system of human platelets. Human plasmin caused a dose- and time-dependent increase in adenylate cyclase activity when added to a crude platelet membrane preparation. Both basal and prostaglandin E1-stimulated adenylate cyclase activity doubled in presence of plasmin. This stimulatory activity was shared by papain and alpha-chymotrypsin, but not by thrombin which displayed a slightly inhibitory effect. Plasmin not only stimulated platelet adenylate cyclase activity, but also suppressed the GTP-dependent alpha 2-adrenergic inhibition, thereby producing a five- to six-fold increased activity measured in the presence of adrenaline and GTP. These effects of plasmin on the adenylate cyclase system were suppressed by the addition of the protease inhibitor leupeptin, and of soybean trypsin inhibitor, indicating that proteolysis mediated these effects. We also examined the adenylate cyclase activity in membranes prepared from intact platelets incubated with increasing doses of plasmin. Incubation of platelets with plasmin concentrations as low as 0.25 mg/ml resulted in an irreversible increase in membrane adenylate cyclase activity and suppression of the adrenaline-mediated inhibition of enzyme activity. These results suggest that the proteolytic stimulating effect of plasmin on the platelet adenylate cyclase system may account for the inhibition of platelet aggregation.
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PMID:Plasmin: a possible physiological modulator of the human platelet adenylate cyclase system. 295 Oct 52

The effect of various proteases (kallikrein, plasmin, and trypsin) on sperm phospholipase A2 activity (PA2: EC 3.1.1.4) has been studied. The addition of trypsin to spermatozoa, isolated and washed in the presence of the protease inhibitor benzamidine, increased PA2 activity optimally with trypsin concentrations of 1.0-1.5 units/assay. In kinetic studies, all of the above proteases stimulated the deacylation of phosphatidylcholine (PC); in fresh spermatozoa, trypsin showed a higher activation potential than kallikrein or plasmin. In the presence of benzamidine, the activity remained at basal levels. Endogenous protease activity due to acrosin (control) resulted in an increase in PC deacylation compared to the basal level. The maximum activation time of PA2 activity by proteases was 30 min. Natural protease inhibitors (soybean trypsin inhibitor and aprotinin) kept the PA2 activity at basal levels and a by-product of kallikrein, bradykinin, did not significantly affect the control level. Protein extracts of fresh spermatozoa exhibited the same pattern of PA2 activation upon the addition of proteases, thus indicating that the increase in PA2 activity was not merely due to the release of the enzyme from the acrosome. All of these findings suggest the presence of a precursor form of phospholipase A2 that can be activated by endogenous proteases (acrosin) as well by exogenous proteases present in seminal plasma and in follicular fluid (plasmin, kallikrein). Thus, this interrelationship of proteases and prophospholipase A2 could activate a dormant fusogenic system: the resulting effect would lead to membrane fusion by lysolipids, key components in the acrosome reaction.
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PMID:Activation of phospholipase A2 of human spermatozoa by proteases. 297 29

Protease nexin-I (PN-I, Mr approximately 43,000) is representative of a newly described class of cell-secreted protease inhibitors. PN-I has been purified to apparent homogeneity, partially sequenced, and monospecific antibodies have been raised against it. PN-I is a potent inhibitor of urokinase, thrombin, plasmin, and trypsin. In addition, cells have specific receptors that mediate the uptake of covalently linked complexes formed between PN-I and its protease substrates. In the present studies, we have investigated the relationship between human PN-I and a protease inhibitor derived from C6 glioma cells in culture that has neurite-promoting activity. On the basis of co-purification on heparin-Sepharose, identical molecular weight, antibody cross-reactivity, and receptor cross-reactivity, we conclude that PN-I and the glioma-cell-derived inhibitor are equivalent molecules.
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PMID:The glioma cell-derived neurite promoting activity protein is functionally and immunologically related to human protease nexin-I. 304 Jul 80

Urokinase-related proteins were purified from 60-liter batches of human urine collected into the protease inhibitor aprotinin to prevent proteolytic degradation. Three homogeneous species were obtained by chromatography on zinc chelate-Sepharose, SP-Sephadex C-50, Sephadex G-100, benzamidine-Sepharose, and immunoadsorption on a murine anti-human urokinase monoclonal antibody. One urokinase-related protein with Mr 95,000 representing a complex of two-chain urokinase with an inhibitor accounts for about 70% of the total urokinase-related antigen in urine. Nucleophilic agents dissociate the complex into active two-chain urokinase and a protein with Mr 45,000-50,000 which is immunologically distinct from urokinase. Approximately 25% of the urinary urokinase-related antigen represents a single-chain molecule with Mr 54,000. This highly purified single-chain molecule was obtained with a yield of 5 micrograms/liter of urine. Only trace amounts (less than 5%) of the urokinase-related antigen were recovered as free two-chain urokinase. The urinary single-chain urokinase-related protein has no specific affinity for fibrin. It has a very low activity on Pyroglu-Gly-Arg-p-nitroanilide, a urokinase-specific synthetic substrate, but directly activates plasminogen following Michaelis-Menten kinetics with Km = 0.7 microM and kcat = 0.0011 S-1. The single-chain molecule is rapidly converted to active two-chain urokinase by plasmin. Active two-chain urinary urokinase has a very high amidolytic activity and activates plasminogen with Km = 60 microM and kcat = 1.4 S-1. It is concluded that the urokinase-related proteins in human urine consist of about 25% of single-chain urokinase (10-20 micrograms/liter) and of about 75% two-chain urokinase (40-50 micrograms/liter), the bulk of which is complexed to an inhibitor. Because even in freshly voided urine most of the urokinase-related antigen is already converted to two-chain urokinase, urine does not seem to be a suitable source for the large-scale purification of single-chain urokinase. In view of the very significant intrinsic plasminogen-activating properties of single-chain urokinase, it should not be considered to be a proenzyme form of urokinase. The dramatic differences of its kinetic constants from those of urokinase render the designation single-chain urokinase equally inadequate. Consequently, the designation "single-chain urokinase-type plasminogen activator" was recently adopted by the International Committee on Thrombosis and Haemostasis (Annual Meeting, San Diego, CA, July 13-14, 1985).
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PMID:Urokinase-related proteins in human urine. Isolation and characterization of single-chain urokinase (pro-urokinase) and urokinase-inhibitor complex. 308 Apr 22

Urokinase-related proteins in human urine occur mainly as a 1:1 complex of urokinase with an inhibitor (Stump, D. C., Thienpont, M., and Collen, D. (1986) J. Biol. Chem. 261, 1267-1273). BALB/c mice were immunized with this urokinase-urokinase inhibitor complex and spleen cells fused with mouse myeloma cells, resulting in hybridomas producing monoclonal antibodies. Three antibodies reacting with the complex but not with urokinase were utilized to develop a sensitive (0.5 ng/ml) enzyme-linked immunosorbent assay for the urokinase inhibitor, which was used for monitoring its purification by chromatography on zinc chelate-Sepharose, concanavalin A-Sepharose, SP-Sephadex C-50, and Sephadex G-100. A homogenous glycoprotein of apparent Mr 50,000 was obtained with a yield of 40 micrograms/liter urine and a purification factor of 320. One mg of the purified protein inhibited 35,000 IU of urokinase within 30 min at 37 degrees C. This protein was immunologically related to both the purified urokinase-urokinase inhibitor complex and to the inhibitor portion dissociated from it by nucleophilic dissociation. It was immunologically distinct from all known protease inhibitors, including the endothelial cell-derived fast-acting inhibitor of tissue-type plasminogen activator, the placental inhibitor of urokinase and protease nexin. In electrophoresis the protein migrated with beta-mobility. Inhibition of urokinase occurred with a second order rate constant (k) of 8 X 10(3) M-1 s-1 in the absence and of 9 X 10(4) M-1 s-1 in the presence of 50 IU of heparin/ml. The urokinase inhibitor was inactive towards single-chain urokinase-type plasminogen activator and plasmin, but it inhibited two-chain tissue-type plasminogen activator with a k below 10(3) M-1 s-1 and thrombin with a k of 4 X 10(4) M-1 s-1 in the absence and 2 X 10(5) M-1 s-1 in the presence of heparin. The concentration of this urokinase inhibitor in plasma from normal subjects determined by immunoassay was 2 +/- 0.7 micrograms/ml (mean +/- S.D., n = 25). The protein purified from plasma by immunoabsorption had the same Mr, amino acid composition, and immunoreactivity as the urinary protein. Furthermore, when urokinase was added to plasma, time-dependent urokinase-urokinase inhibitor complex formation was observed at a rate similar to that observed for the inhibition of urokinase by the purified inhibitor from urine. This urokinase inhibitor, purified from human urine, most probably represents a new plasma protease inhibitor.
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PMID:Purification and characterization of a novel inhibitor of urokinase from human urine. Quantitation and preliminary characterization in plasma. 309 4

An inhibitor of factor XIIa has been purified to homogeneity from bovine plasma. The purification steps included precipitation of contaminating proteins with polyethylene glycol and chromatography on DEAE-cellulose, Affi-Gel blue, and immobilized wheat germ lectin. The apparent molecular weight of the XIIa inhibitor (called INH1) was 85,000, reduced, and 92,000, nonreduced, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The extinction coefficient (E0.1%(280)) of INH1 is 1.3, and the protein contains 17.7% carbohydrate. Purified antibody to INH1 raised in either rabbits or chickens formed a precipitin line of identity with purified INH1 and a component of bovine plasma, but there was no reaction with purified human inhibitors or with any component of human plasma. INH1 inhibits bovine and human XIIa, bovine and human C1-esterase, and human kallikrein, but does not inhibit bovine kallikrein, bovine trypsin, human plasmin, or human thrombin. This activity is similar to that of C1-inhibitor but different from antithrombin III, alpha 2-antiplasmin, or alpha 1-protease inhibitor. INH1 at a physiological concentration (0.47 microM) causes rapid inactivation of XIIa. The two molecules react in a 1:1 stoichiometry with a second-order rate constant of 1.23 X 10(6) M-1 min-1.
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PMID:Isolation and characterization of an inhibitor of factor XIIa from bovine plasma. 311 62

The nature of vascular permeability factor (VPF) activity derived from serum-free conditioned medium containing cultured human malignant glial tumors has been further investigated. A 1000-fold purification was accomplished by sequential heparin-Sepharose affinity chromatography and high-performance liquid chromatography gel filtration chromatography steps. Vascular permeability factor activity falls into a molecular weight range of 41,000 to 56,000 D. Activity is bound to hydroxylapatite, carboxymethyl-Sepharose, phenyl-Sepharose, and heparin-Sepharose, whereas little or no activity was bound to diethylaminoethyl-Sephacel. Vascular permeability factor activity is trypsin- and pepsin-sensitive but is unaffected by treatment with ribonuclease A. This suggests that VPF is a hydrophobic, positively charged (cationic) polypeptide with a potentially biologically significant affinity for heparin. As most proteins are negatively charged (anionic) and have no affinity for heparin, a significant advantage was gained by performing these purification steps. The activity of VPF is not inhibited by coinjection of conditioned medium with soybean trypsin inhibitor; or hexadimethrine (both known antagonists of tissue plasminogen activator, Hageman factor, and serum kallikrein); or aprotinin (an antagonist of both plasmin and tissue kallikrein); or phenylmethanesulfonyl fluoride (a serine esterase (elastase) inhibitor); or pepstatin-A (an acid protease inhibitor which inactivates vascular permeability-inducing leukokinins). These data, together with the fact that VPF is produced and released into serum-free media, provides substantial evidence against it being one of the more commonly known serum-derived permeability mediators. Treatment with dithiothreitol inhibited VPF activity, indicating the presence of at least one essential disulfide bond in this molecule. Inhibition by dexamethasone of VPF expression in cultured malignant glial cells appears to be selective. Dexamethasone-induced inhibition of VPF was dose-responsive and was not associated with a parallel inhibition of cellular protein synthesis as determined by tritiated leucine incorporation into trichloroacetic acid-precipitable material. Inclusion of dexamethasone in the culture medium was not associated with altered cell viability or cell number. A series of in vivo studies confirmed the inhibition of VPF activity in test animals pretreated with dexamethasone. This steroid-induced inhibition was partially reversed by treatment of test animals with actinomycin D prior to exposure to dexamethasone.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Further characterization of malignant glioma-derived vascular permeability factor. 313 21

Protease nexin-1 (PN-1) is a protease inhibitor that is secreted by fibroblasts and several other cultured cells. PN-1 forms complexes with certain serine proteases in the extracellular environment including thrombin, urokinase, and plasmin. The complexes then bind to the cells and are rapidly internalized and degraded. This report demonstrates that PN-1 is present on the surface of fibroblasts, bound to the extracellular matrix. Immunofluorescent studies showed that PN-1 colocalized with fibronectin on both intact cells and in preparations of extracellular matrix made from these cells. In contrast, PN-1 did not colocalize with the epidermal growth factor receptor, a plasma membrane marker. An enzyme-lined immunosorbent assay was developed which showed that the extracellular matrix contained at least 60-80% of the cellular immunoreactive PN-1. Extraction of the matrix with 2 M NaCl removed PN-1 in a form which reacted with 125I-thrombin to form complexes which were immunoprecipitated by anti-PN-1 IgG and were of identical size as complexes made from soluble PN-1 and 125I-thrombin. These data indicate that in addition to its role as a soluble protease inhibitor, PN-1 is also a component of the extracellular matrix and might control its proteolysis.
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PMID:Localization of protease nexin-1 on the fibroblast extracellular matrix. 327 57

A low molecular weight protein protease inhibitor was purified from Japanese horseshoe crab (Tachypleus tridentatus) hemocytes. It consisted of a single polypeptide with a total of 61 amino acid residues. This protease inhibitor inhibited stoichiometrically the amidase activity of trypsin (Ki = 4.60 X 10(-10) M), and also had inhibitory effects on alpha-chymotrypsin (Ki = 5.54 X 10(-9) M), elastase (Ki = 7.20 X 10(-8) M), plasmin, and plasma kallikrein. However, it had no effect on T. tridentatus clotting enzyme and factor C, mammalian blood coagulation factors (activated protein C, factor Xa and alpha-thrombin), papain, and thermolysin. The complete amino acid sequence of this inhibitor was determined and its sequence was compared with those of bovine pancreatic trypsin inhibitor (BPTI) and other Kunitz-type inhibitors. It was found that the amino acid sequence of this inhibitor has a high homology of 47 and 43% with those of sea anemone inhibitor 5-II and BPTI, respectively. Thus, this protease inhibitor appeared to be one of the typical Kunitz-type protease inhibitors.
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PMID:Purification and amino acid sequence of Kunitz-type protease inhibitor found in the hemocytes of horseshoe crab (Tachypleus tridentatus). 330 64

Protease and antiprotease activities were estimated in nasal secretions from patients with chronic sinusitis and nasal allergy, using [3H]-casein as substrate. In the purulent nasal secretions, strong protease activity was measured, but there was less activity in the allergic nasal secretions. In contrast, trypsin inhibitory activity in allergic nasal secretions was much higher than in nasal secretions from the patients with chronic sinusitis. A protease inhibitor was partially isolated from nasal secretions of the nasal allergic patients by Sephadex G-150 gel chromatography and characterized. This protease inhibitor has an apparent molecular weight of 10,000 D, determined by SDS-polyacrylamidegel electrophoresis. It depresses the activities of bovine pancreatic trypsin, bovine pancreatic chymotrypsin and proteases in nasal purulent secretions, whereas it does not inhibit porcine pancreatic elastase, papain, or human plasmin.
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PMID:A protease inhibitor from human allergic nasal secretions. 332 29


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