Plasminogen and plasmin

Broad substrate affinity and catalytic diversity of fibrinolytic enzyme from Pheretima posthumous-Purification and molecular characterization study

In this research, a serine protease was isolated and purified from Indian earthworm Pheretima posthumous by fractionation with ammonium sulfate followed by ion exchange and size exclusion chromatography. The molecular weight of purified protease was determined 29.5kDa by Maldi-TOF/MS. The enzyme exhibited a maximum proteolytic activity of 1.2U/ml with specific activity of 17.65U/mg at pH 8 and temperature 40°C. 2D electrophoresis study illustrated purity of enzyme, purified as a single peptide and isoelectric point (pI) 4.5. The enzyme has shown tremendous stability and proteolytic activity in the wide range of pH range (4-12) and temperatures (20-60°C). The kinetic constant Km and Vmax of purified protease were reported 0.09mg/ml and 23.25mg/ml/min. The enzyme also possesses excellent catalytic capacity with Kcat (341.9min^-1) and catalytic efficiency (3798.88). The N-terminal sequence of purified protease Arg-Lys-Lys-Gly-Ala-Ser-Try-Phe-Try-Pro-Trp-Ser-Val-Lys-Lys-Arg, PMF and MS/MS studies had shown a partial homology with Lumbrokinase-P2 (2) from Lumbricus rubellus. The CD spectroscopy result provided an evidence for broad substrate affinity and stability of enzyme. The different forms of secondary structures determined in EFE result broad substrate affinity of enzyme.

Leach-proof magnetic thrombolytic nanoparticles and coatings of enhanced activity

Despite the fact that magnetic thrombolytic composites is an emerging area, all known so far systems are based on the similar mechanism of action: thrombolytic enzyme releases from the magnetic carrier leaving non-active matrix, thus making the whole system active only for a limited period of time. Such systems often have very complex structure organization and composition, consisting of materials not approved for parenteral injection, making them poor candidates for real clinical trials and implementation. Here we report, for the first time, the production of thrombolytic magnetic composite material with non-releasing behavior and prolonged action. Obtained composite shows good thrombolytic activity, consists of fully biocompatible materials and could be applied as infinitely active thrombolytic coatings or magnetically-targetable thrombolytic agents.

Rapid extraction and purification of lumbrokinase from Lumbricus rubellus using a hollow fiber membrane and size exclusion chromatography

OBJECTIVES

To develop a purification process using hollow fiber membrane separation combined with size exclusion chromatography for the extraction of lumbrokinase from earthworms (Lumbricus rubellus).

RESULTS

To extract the protein, the earthworms were first homogenized for 10 min, to produce ultrafine particles. Polyether sulfone hollow fiber membranes with MW cut offs of 50 and 6 kDa were used for initial purification of the crude extract. Further purification was carried out on a Sephadex G-75 column, and yielded three fractions of high purity protein. One of these fractions showed fibrinolytic activity.

CONCLUSIONS

Three samples of high purity protein were obtained and one protein (LK1) showed strong fibrinolytic activity. The method has higher purification efficiency in comparison with existing methods.

Porphyromonas gingivalis-derived RgpA-Kgp Complex Activates the Macrophage Urokinase Plasminogen Activator System: IMPLICATIONS FOR PERIODONTITIS

Urokinase plasminogen activator (uPA) converts plasminogen to plasmin, resulting in a proteolytic cascade that has been implicated in tissue destruction during inflammation. Periodontitis is a highly prevalent chronic inflammatory disease characterized by destruction of the tissue and bone that support the teeth. We demonstrate that stimulation of macrophages with the arginine- and lysine-specific cysteine protease complex (RgpA-Kgp complex), produced by the keystone pathogen Porphyromonas gingivalis, dramatically increased their ability to degrade matrix in a uPA-dependent manner. We show that the RgpA-Kgp complex cleaves the inactive zymogens, pro-uPA (at consensus sites Lys(158)-Ile(159) and Lys(135)-Lys(136)) and plasminogen, yielding active uPA and plasmin, respectively. These findings are consistent with activation of the uPA proteolytic cascade by P. gingivalis being required for the pathogen to induce alveolar bone loss in a model of periodontitis and reveal a new host-pathogen interaction in which P. gingivalis activates a critical host proteolytic pathway to promote tissue destruction and pathogen virulence.

Activation method does not alter abnormal placental gene expression and development in cloned pigs

Nuclear transfer efficiency is low and is thought to be caused by inadequate placental development. The objective of this study was to identify differentially expressed transcripts in pig placentas derived from in vivo fertilization, in vitro fertilization or nuclear transfer at Day 30 of gestation. Three activation methods were compared: electrical fusion/activation, electrical fusion/activation followed by treatment with reversible proteasomal inhibitor, MG132 or electrical fusion followed by activation with Thimerosal/DTT. Extraembryonic membranes were collected 30 days after artificial insemination (IVV) or embryo transfer (IVF and NT). Extraembryonic membrane cDNAs labeled with Cy5 and a reference cDNA labeled with Cy3 were hybridized to a pig reproductive tissue-specific 19,968 spot cDNA microarray. Images acquired and assessed by using Genepix Pro 4.0 were analyzed by Genespring 7.3.1. ANOVA (P < 0.05) identified 227 differentially expressed transcripts between the five treatments and 0 between the three activation methods. The nuclear transfer groups were pooled and compared to in vivo samples, identifying 34 up- and 19 down-regulated transcripts (>2-fold change, P < 0.05). Ten transcripts were validated by real-time PCR. UPTI, PAG2, and GLUD1 protein was quantified by Western blot and densitometry verified that UPTI and PAG2 proteins had an expression pattern that mirrored mRNA abundance (P < 0.05). Localization patterns were also determined for UPTI, PAG2, GLUD2 and 14-3-3 gamma in Day 35 extraembryonic membranes. Observed differences in gene and protein expression in nuclear transfer extraembryonic membranes indicate that an impaired fetal-maternal interface, and not the activation method, may be causing defects observed in cloned pigs.

Antithrombotic effects by oral administration of novel proteinase fraction from earthworm Eisenia andrei on venous thrombosis model in rats

A novel proteinase fraction, SPP-501, was purified from the earthworm, Eisenia andrei, and its antithrombotic effects compared with those of urokinase and t-PA (tissue type-plasminogen activator) in a thrombosis model, induced by the insertion of a stainless wire coil into the inferior vena cava. SPP-501, urokinase and t-PA were administrated once a day for 14 days. On the oral administration of SPP-501, as well as urokinase and t-PA, the thrombus weight was dramatically decreased. The euglobulin lysis time (ELT) was also shortened by SPP-501, but urokinase and t-PA failed to dissolve the euglobulin clot. Conversely, urokinase and t-PA produced detectable fibrinogen/fibrin degradation products (FDP), but SPP-501 did not. Thrombin induced platelet aggregation was desensitized in the SPP-501 treatment groups. With a high dose of SPP-501 (45 mg/kg), the APTT (activated partial thromboplastin time) was prolonged. These results suggest that SPP-501 shows both antithrombotic and fibrinolytic activities when orally administered.

Purification and Characterization of Six Fibrinolytic Serine-Proteases from Earthworm Lumbricus rubellus

The six lumbrokinase fractions (F1 to F6) with fibrinolytic activities were purified from earthworm Lumbricus rubellus lysates using the procedures of autolysis, ammonium sulfate fractionation, and column chromatography. The proteolytic activities on the casein substrate of the six iso-enzymes ranged from 11.3 to 167.5 unit/mg with the rank activity orders of F2 > F1 > F5 > F6 > F3 > F4. The fibrinolytic activities of the six fractions on the fibrin plates ranged from 20.8 to 207.2 unit/mg with rank orders of F6 > F2 > F5 > F3 > F1 > F4. The molecular weights of each iso-enzyme, as estimated by SDS-PAGE, were 24.6 (F1), 26.8 (F2), 28.2 (F3), 25.4 (F4), 33.1 (F5), and 33.0 kDa (F6), respectively. The plasminogen was activated into plasmin by the enzymes. The optimal temperature of the six iso-enzymes was 50 degrees C, and the optimal pH ranged from pH 4-12. The four iso-enzymes (F1-F4) were completely inhibited by PMSF. The two enzymes (F5 and F6) were completely inhibited by aprotinin, TLCK, TPCK, SBTI, LBTI, and leupeptin. The N-terminal amino acid (aa) sequences of the first 20 to 22 residues of each fraction had high homology. All six iso-enzymes had identical aa residues 2-3 and 13-15. The N-terminal 21-22 aa sequences of the F2, F3, and F4 iso-enzymes were almost the same. The N-terminal aa sequences of F5 and F6 were identical.

Thrombolytic potency of acid-stabilized plasmin: superiority over tissue-type plasminogen activator in an in vitro model of catheter-assisted thrombolysis

Plasmin, the direct fibrinolytic enzyme, was compared with tissue plasminogen activator (t-PA) in an in vitro thrombolysis model. Plasmin has been prepared in a highly pure form from human plasma and has been stabilized against auto-degradation by low-pH formulation. This acidified formulation of plasmin has been designed to have a low buffering capacity so that it can be directly infused into clots in a stable and latently active form. This low-pH formulation has been shown to be equivalent to a neutral-pH formulation of plasmin in its extent of clot lysis. An in vitro model of catheter-assisted thrombolysis has been devised in which large (12 x 0.6 cm), retracted clots are treated with an intrathrombus thrombolytic agent via a multi-sideport catheter. Plasmin dissolves these plasminogen-deficient clots in a dose-dependent manner and is clearly superior to t-PA. In this model system, t-PA exhibits efficacy only when retracted clots are replenished with plasminogen.

Distinct dose-dependent effects of plasmin and TPA on coagulation and hemorrhage

All thrombolytic agents in current clinical usage are plasminogen activators. Although effective, plasminogen activators uniformly increase the risk of bleeding complications, especially intracranial hemorrhage, and no laboratory test is applicable to avoid such bleeding. We report results of a randomized, blinded, dose-ranging comparison of tissue-type plasminogen activator (TPA) with a direct-acting thrombolytic agent, plasmin, in an animal model of fibrinolytic hemorrhage. This study focuses on the role of plasma coagulation factors in hemostatic competence. Plasmin at 4-fold, 6-fold, and 8-fold the thrombolytic dose (1 mg/kg) induced a dose-dependent effect on coagulation, depleting antiplasmin activity completely, then degrading fibrinogen and factor VIII. However, even with complete consumption of antiplasmin and decreases in fibrinogen and factor VIII to 20% of initial activity, excessive bleeding did not occur. Bleeding occurred only at 8-fold the thrombolytic dose, on complete depletion of fibrinogen and factor VIII, manifest as prolonged primary bleeding, but with minimal effect on stable hemostatic sites. Although TPA had minimal effect on coagulation, hemostasis was disrupted in a dose-dependent manner, even at 25% of the thrombolytic dose (1 mg/kg), manifest as rebleeding from hemostatically stable ear puncture sites. Plasmin degrades plasma fibrinogen and factor VIII in a dose-dependent manner, but it does not disrupt hemostasis until clotting factors are completely depleted, at an 8-fold higher dose than is needed for thrombolysis. Plasmin has a 6-fold margin of safety, in contrast with TPA, which causes hemorrhage at thrombolytic dosages.

Plasmin activates pro-matrix metalloproteinase-2 with a membrane-type 1 matrix metalloproteinase-dependent mechanism

Membrane-type 1 matrix metalloproteinase (MT1-MMP) has been implicated as a physiological activator of progelatinase A (MMP-2). We previously reported that plasmin treatment of cells results in proMMP-2 activation and increased type IV collagen degradation. Here, we analyzed the role of MT1-MMP in plasmin activation of MMP-2 using HT-1080 cells transfected with MT1-MMP sense or antisense cDNA. Control, vector-transfected cells that expressed endogenous MT1-MMP, and antisense cDNA transfectants with very low levels of MT1-MMP did not activate proMMP-2. Conversely, cells transfected with sense MT1-MMP cDNA expressed high MT1-MMP levels and processed proMMP-2 to 68/66-kDa intermediate activation products. Control cells and MT1-MMP transfectants had much higher levels of cell-associated MMP-2 than antisense cDNA transfectants. Addition of plasmin(ogen) to control or MT1-MMP-transfected cells generated active, 62-kDa MMP-2, but was ineffective with antisense cDNA transfectants. The effect of plasmin(ogen) was prevented by inhibitors of plasmin, but not by metalloproteinase inhibitors, implicating plasmin as a mechanism for proMMP-2 activation independent of the activity of MT1-MMP or other MMPs. Plasmin-mediated activation of proMMP-2 did not result from processing of proMT1-MMP and did not correlate with alpha(v)beta(3) integrin or TIMP-2 levels. Thus, plasmin can activate proMMP-2 only in the presence of MT1-MMP; however, this process does not require the catalytic activity of MT1-MMP.

Purification and partial characterisation of alpha(2)-antiplasmin and plasmin(ogen) from ostrich plasma

This study reports the isolation and partial characterisation of the ostrich serpin, alpha(2)AP, and its target enzyme, ostrich plasmin, in its active and inactive proenzyme, namely plasminogen, forms. Ostrich alpha(2)AP was purified using L-lysine-Sepharose chromatography, ammonium sulfate fractionation, and Super Q-650S and ostrich LBSI-Sepharose chromatographies. It revealed a M(r) of 84 K (thousand) and had one and two N-terminal amino acids in common with 11 of those of human and bovine alpha(2)AP, respectively. It showed the largest inhibitory effect on ostrich plasmin, followed by bovine trypsin and plasmin, respectively, and much less plasmin inhibition than bovine aprotinin, but much more so than human alpha(2)AP, DFP and EACA. Ostrich plasminogen was highly purified after L-lysine-Sepharose chromatography and showed a M(r) of 92 K, a total of 775 amino acids and its N-terminal sequence showed approximately 53% identity with those of human, rabbit, cat, and ox plasminogens. Ostrich plasmin, obtained by the urokinase-activation of ostrich plasminogen, revealed a M(r) of 78 K, a total of 638 amino acids, an N-terminal sequence showing two to four residues identical to five of those of human, cat, dog, rabbit, and ox plasmins, and pH and temperature optima of 8.0 and 40 degrees C, respectively.

Zymogen activation in the streptokinase-plasminogen complex. Ile1 is required for the formation of a functional active site

Plasminogen (Plgn) is usually activated by proteolysis of the Arg561-Val562 bond. The amino group of Val562 forms a salt-bridge with Asp740, which triggers a conformational change producing the active protease plasmin (Pm). In contrast, streptokinase (SK) binds to Plgn to produce an initial inactive complex (SK.Plgn) which subsequently rearranges to an active complex (SK.Plgn*) although the Arg561-Val562 bond remains intact. Therefore another residue must substitute for the amino group of Val562 and provide a counterion for Asp740 in this active complex. Two candidates for this counterion have been suggested: Ile1 of streptokinase and Lys698 of Plgn. We have investigated the reaction of SK mutants and variants of the protease domain of microplasminogen (muPlgn) in order to determine if either of these residues is the counterion. The mutation of Ile1 of SK decreases the activity of SK.Plgn* by 100-fold (Ile1Val) to >/= 104-fold (Ile1-->Ala, Gly, Trp or Lys). None of these mutations perturb the binding affinity of SK, which suggests that Ile1 is not required for formation of SK.Plgn but is necessary for SK.Plgn*. The substitution of Lys698 of muPlgn decreases the activity of SK.Plgn* by only 10-60-fold. In contrast with the Ile1 substitutions, the Lys698 mutations also decreased the dissociation constant of the SK complex by 15-50-fold. These observations suggest that Lys698 is involved in formation of the initial SK.Plgn complex. These results support the hypothesis that Ile1 provides the counterion for Asp740.

The inhibitory properties and primary structure of a novel serine proteinase inhibitor from the fruiting body of the basidiomycete, Lentinus edodes

A novel proteinase inhibitor, Lentinus proteinase inhibitor, has been purified from the fruiting bodies of the edible mushroom, Lentinus edodes, by buffer extraction and affinity chromatography on immobilized anhydrotrypsin. The protein simultaneously inhibits bovine beta-trypsin and alpha-chymotrypsin at independent sites, with apparent dissociation constants of 3.5 x 10(-10) M and 4 x 10(-8) M, respectively. The purified protein is eluted as two well-separated peaks on reversed-phase HPLC, one of which is inhibitory-active and the other inactive, and they are interconvertible under folding/unfolding conditions. Among the mammalian and microbial serine proteinases examined, including human enzymes of blood coagulation and fibrinolysis, activated factor XI was inhibited by the Lentinus proteinase inhibitor. Chemical modification studies suggest involvement of one or more arginine residues in the inhibition of trypsin. The complete primary structure composed of 142 amino acids with an acetylated N-terminus was determined by protein analysis. The theoretical molecular mass (15999.2) from the sequence is close to the experimental value of 15999.61 +/- 0.61 determined by mass spectrometry. Although there are no apparently homologous proteinase inhibitors in the protein database, there is a rather striking similarity to the propeptide segment of a microbial serine proteinase, as well as to the N-terminal region of the mature enzyme.

The relationship between the fibrinogen D domain self-association/cross-linking site (gammaXL) and the fibrinogen Dusart abnormality (Aalpha R554C-albumin): clues to thrombophilia in the "Dusart syndrome"

Cross-linking of fibrinogen at its COOH-terminal gamma chain cross-linking site occurs in the presence of factor XIIIa due to self-association at a constitutive D domain site ("gammaXL"). We investigated the contribution of COOH-terminal regions of fibrinogen Aalpha chains to the gammaXL site by comparing the gamma chain cross-linking rate of intact fibrinogen (fraction I-2) with that of plasma fraction I-9, plasmic fraction I-9D, and plasmic fragment D1, which lack COOH-terminal Aalpha chain regions comprising approximately 100, approximately 390, and 413 residues, respectively. The cross-linking rates were I-2 > I-9 > 1-9D = D1, and indicated that the terminal 100 or more Aalpha chain residues enhance gammaXL site association. Fibrinogen Dusart, whose structural abnormality is in the COOH-terminal "alphaC" region of its Aalpha chain (Aalpha R554C-albumin), is associated with thrombophilia ("Dusart Syndrome"), and is characterized functionally by defective fibrin polymerization and clot structure, and reduced plasminogen binding and tPA-induced fibrinolysis. In the presence of XIIIa, the Dusart fibrinogen gamma chain cross-linking rate was about twice that of normal, but was normalized in proteolytic fibrinogen derivatives lacking the Aalpha chain abnormality, as was reduced plasminogen binding. Electron microscopy showed that albumin-bound Dusart fibrinogen "alphaC" regions were located in the vicinity of D domains, rather than at their expected tethered location near the fibrinogen E domain. In addition, there was considerable fibrinogen aggregation that was attributable to increased intermolecular COOH-terminal Aalpha chain associations promoted by untethered Dusart fibrinogen aC domains. We conclude that enhanced Dusart fibrinogen self-assembly is mediated through its abnormal alphaC domains, leads to increased gammaXL self-association and gamma chain cross-linking potential, and contributes to the thrombophilia that characterizes the "Dusart Syndrome."

Enhancement of plasma fibrinolysis in vitro by jararhagin, the main haemorrhagic metalloproteinase in Bothrops jararaca venom

Jararhagin, a haemorrhagic metalloproteinase from Bothrops jararaca venom, plays an important role in systemic as well as local haemorrhage. In this study, the effect of jararhagin on the fibrinolytic system was investigated. The fibrinolytic activity of various kinds of animal plasmas was measured by the fibrin plate method. No activity was detected in plasma alone. However, after mixing plasma with jararhagin, strong fibrinolytic activity was recorded in guinea-pig, horse, dog, rabbit and human plasmas. The mechanism of the increase of firbinolytic activity by jararhagin was studied further in guinea-pig plasma. Fibrin-zymographic studies indicated that jararhagin increased tissue-type plasminogen activator (tPA) activity by the dissociation of a complex of tPA with type 1 plasminogen activator inhibitor (PAI-1). alpha 2-Plasmin inhibitor (alpha 2-PI) activity in the plasma was measured using a synthetic chromogenic substrate method after incubation with jararhagin. The alpha 2-PI activity in the plasma decreased in both time-dependent and dose-dependent manners. These in vitro results suggest that, in some animal plasmas, jararhagin increases plasma fibrinolytic activity by causing dissociation of the tPA/PAI-1 complex and by the inactivation of alpha 2-PI. It is possible that this direct action of jararhagin on the enhancement of plasma fibrinolytic activity may contribute to the aetiology of systemic haemorrhage frequently observed in human victims of B. jararaca envenoming.

Changes in the hemagglutinin gene of the neurovirulent influenza virus strain A/NWS/33

The neurovirulent strain of influenza A virus, A/NWS/33, is able to infect a large range of cell types, including mouse brain cells, which are not infected by its parent, A/WS/33. This seems to be largely due to the hemagglutinin of A/NWS/33. The complete nucleotide sequence of the HA genes of both strains has been determined and a comparison revealed a number of changes. Analysis showed that the virulence capabilities of the NWS HA involve at least three different mechanisms: (a) loss of a glycosylation site; (b) a change at the cleavage site; and (c) a substitution in HA2, which may increase the pH of fusion.

Function of streptokinase fragments in plasminogen activation

Several peptide fragments of streptokinase (SK) were prepared by incubating SK with immobilized human plasmin (hPlm) and purified by h.p.l.c. with a reverse-phase phenyl column. The N-terminal sequences, amino acid compositions and molecular masses of these peptide fragments were determined. The SK peptide fragment of 36 kDa consisting of Ser60-Lys387 (SK-p), was the only peptide fragment that could be tightly bound to immobilized hPlm. Another three large SK peptide fragments, SK-m, SK-n and SK-o, with molecular masses of 7 kDa, 18 kDa and 30 kDa, and consisting of Ile1-Lys59, Glu148-Lys333, Ser60-Lys333 respectively, were also obtained from the supernatant of the reaction mixture. The purified SK-p had high affinity with hPlm and could activate human plasminogen (hPlg) with a kPlg one-sixth that of the native SK. SK-o had low affinity with hPlm and could also activate hPlg, although the catalytic constant was less than 1% of the native SK. SK-n, as well as SK-m, which is the N-terminal 59 amino acid peptide of the native SK, had no activator activity. However, SK-m could enhance the activator activity of both SK-o and SK-p and increase their second-order rate constants by two- and six-fold respectively. It was concluded from these studies that (1) SK-o, the Ser60-Lys333 peptide of SK, was essential for minimal SK activator activity, (2) the C-terminal peptide of SK-p, Ala334-Lys387, was essential for high affinity with hPlm, and (3) the N-terminal 59-amino-acid peptide was important in maintaining the proper conformation of SK to have its full activator activity.

Conformations and stabilities of human Glu1- and Lys78-plasminogen and of the fragments mini- and microplasminogen, analysed by circular dichroism and differential scanning calorimetry

The conformations and stabilities of two forms of human plasminogen, Glu1-plasminogen (Glu1-HPg, Glu1-Asn791) and Lys78-plasminogen (Lys78-HPg, Lys78-Asn791), and two enzymatically derived plasminogen fragments, miniplasminogen (mini-HPg, Val443-Asn791) and microplasminogen (micro-HPg, Lys531-Asn791) were analysed by circular dichroism and differential scanning calorimetry. The two plasminogen forms differ by the lack of 77 N-terminal amino acids in Lys78-HPg in comparison to Glu1-HPg. Mini-HPg is composed of kringle 5 and the protease domain of HPg whereas micro-HPg is built from the protease domain of HPg and a stretch of about 15 amino acids from kringle 5. Differential scanning calorimetric measurements of Glu1-HPg and Lys78-HPg reveal seven thermal transitions for both plasminogen forms. The results obtained for Lys78-HPg largely agree with recently published data (Novokhatny, V. V., Kudinov, S. A. and Privalov, P. L. J. Mol. Biol. 1984, 179, 215). Three thermal transitions corresponding to kringle 5 and to two subdomains of the C-terminal protease region were identified for mini-HPg. In micro-HPg, the two thermal transitions of the protease region were found but one of the protease subdomains was modified and its stability was much higher than in any of the other studied proteins. According to the microcalorimetric data obtained for mini-HPg and micro-HPg, transitions 5 and 6 of Glu1-HPg and Lys78-HPg were reassigned to kringle 5 and to a subdomain of the protease region, respectively, in contrast to literature data.(ABSTRACT TRUNCATED AT 250 WORDS)

Selection of monoclonal antibodies that bind and inhibit tissue-type plasminogen activator

Three monoclonal antibodies raised against tissue-type plasminogen activator (t-PA) were selected for their ability to inhibit solid-phase bound t-PA. Each monoclonal antibody blocked the release of p-nitroaniline from H-D-Ile-Pro-Arg-pNA (S-2288). The first antibody 1D2 was a gamma 2b, kappa with KD = 8 x 10(-9) M, the second antibody 2B9 was a gamma 1, kappa with KD = 2 x 10(-9) M, and the third antibody 5A9 was a gamma 1,kappa with KD = 4 x 10(-10) M. In solution-phase format each antibody blocked the conversion of plasminogen to plasmin as judged by a plasmin assay and also inhibited t-PA-mediated lysis of plasma fibrin clot in plasma. The binding of each 125I-radiolabeled antibody to t-PA was inhibited by any one of the three antibodies, suggesting that they recognized a common epitope on t-PA which was absent on unfolded t-PA. We concluded these antibodies bind near t-PA active site since PPACK treatment lowered binding of two antibodies. We believe solid-phase chromogenic substrate assay may be a useful way to screen for antibodies directed against the active site of proteases.

The binding of plasminogen fragments to cultured human umbilical vein endothelial cells

Glu-plasminogen, kringle 1-5, kringle 1-3, and miniplasminogen exhibited strong binding to human umbilical vein endothelial cells (HUVEC). On the other hand, no significant binding was obtained with microplasminogen and kringle 4. Kringle 1-5 and miniplasminogen, which both contained kringle 5, specifically inhibited the binding of plasminogen to HUVEC while kringle 1-3 did not. The results implied plasminogen molecule contained at least two binding sites, with which it interacted HUVEC. The stronger binding site was located in kringle 5 and the weaker one was in kringle 1-3. Kringle 4 and the active site domain exhibited no significant binding to HUVEC. The interaction of plasminogen with HUVEC is mainly through binding site on kringle 5.

Lipoprotein (a) inhibits the generation of transforming growth factor beta: an endogenous inhibitor of smooth muscle cell migration

Conditioned medium (CM) derived from co-cultures of bovine aortic endothelial cells (BAECs) and bovine smooth muscle cells (BSMCs) contains transforming growth factor-beta (TGF-beta) formed via a plasmin-dependent activation of latent TGF-beta (LTGF beta), which occurs in heterotypic but not in homotypic cultures (Sato, Y., and D. B. Rifkin. 1989. J. Cell Biol. 107: 1199-1205). The TGF-beta formed is able to block the migration of BSMCs or BAECs. We have found that the simultaneous addition to heterotypic culture medium of plasminogen and the atherogenic lipoprotein, lipoprotein (a) (Lp(a)), which contains plasminogen-like kringles, inhibits the activation of LTGF-beta in a dose-dependent manner. The inclusion of LDL in the culture medium did not show such an effect. Control experiments indicated that Lp(a) does not interfere with the basal level of cell migration, the activity of exogenous added TGF-beta, the release of LTGF-beta from cells, the activation of LTGF-beta either by plasmin or by transient acidification, or the activity of plasminogen activator. The addition of Lp(a) to the culture medium decreased the amount of plasmin found in BAECs/BSMCs cultures. Similar results were obtained using CM derived from cocultures of human umbilical vein endothelial cells and human foreskin fibroblasts. These results suggest that Lp(a) can inhibit the activation of LTGF-beta by competing with the binding of plasminogen to cell or matrix surfaces. Therefore, high plasma levels of Lp(a) might enhance smooth muscle cell migration by decreasing the levels of the migration inhibitor TGF-beta thus contributing to generation of the atheromatous lesions.

Activation of human and bovine plasminogens by the microplasmin and streptokinase complex

Human microplasmin is a catalytically active fragment of human plasmin. It consists of a 31-residue C-terminal peptide derived from the A chain bound through two disulfide bonds to the intact B chain of plasmin. It has similar amidolytic and proteolytic activities as the native human Lys-plasmin on a molar basis. Human microplasmin can form a complex with streptokinase, in a one to one stoichiometry, like the native human Lys-plasmin. The stoichiometric human microplasmin and streptokinase complex is an efficient activator of bovine plasminogen which can not be activated by streptokinase alone. The formation of human microplasmin.streptokinase complex was also directly demonstrated by a gel filtration column chromatography. Moreover, bovine plasminogen can not be activated by a mixture of bovine or porcine microplasmin and streptokinase. The equimolar complex of human microplasmin.streptokinase, human Lys-plasmin.streptokinase, or streptokinase alone has the same activator activity toward human Lys-plasminogen. The human microplasmin.streptokinase complex, however, has a significantly higher activator activity than human Lys-plasmin.streptokinase complex or streptokinase alone toward human Glu-plasminogen. The direct interaction between streptokinase and light chain domain of human plasmin is demonstrated in the complex formation. The difference in the activator activities of plasmins from various animal sources in complex with streptokinase therefore might be due to the difference in the compositions of light chains of plasmins.

A streptokinase dependent plasma factor (SKDF) induces leucocyte tissue factor activity

Various inducers endow human leucocytes with a procoagulant activity of tissue factor type. We have observed a novel plasma factor which in combination with streptokinase induces powerful leucocyte procoagulant activity. This streptokinase dependent factor (SKDF) is present in normal plasma or serum albeit quantitatively different in individual donors. The generation of tissue factor activity as a function of streptokinase-plasma complex shows a specific and saturable sigmoidal dose-response curve. The Hill plot shows a straight line with Hill coefficient, H = 2.2, suggesting a strong positive cooperativity for the binding of this streptokinase-plasma complex to the leucocyte surface receptor for the signal transduction leading to the biosynthesis of tissue factor apoprotein. It also suggests that the leucocyte surface receptor for streptokinase-plasma complex differs from that for endotoxin lipopolysaccharides. SKDF is of apparent high molecular weight. It does not appear to be an antibody to streptokinase since its level does not correlate with the level of antibodies to streptokinase, and it does not correlate with the antistreptolysin titre. Furthermore, SKDF does not bind to protein A. It has a narrow pH range of stability, and is destroyed at 56 degrees C, or at freeze-drying, Urokinase, another plasminogen activator, or plasmin were unable to activate SKDF to induce the leucocyte procoagulant activity. SKDF may play a role in thrombolytic therapy.

Immunomodulation by alpha 2-macroglobulin and alpha 2-macroglobulin-proteinase complexes: the effect on the human T lymphocyte response

Alpha 2-macroglobulin (alpha 2M), various alpha 2M-proteinase complexes and methylamine-treated alpha 2M were added to human lymphocyte cultures stimulated with the specific antigen purified protein derivative of tuberculin (PPD), pokeweed mitogen (PWM) and anti-CD3. alpha 2M-trypsin diminished all reactions in a dose-dependent way. In the PPD-induced stimulation of peripheral blood mononuclear cells, both change of configuration and remaining proteinase activity contributed to the suppressive activity. Separate exposure of adherent cells or the highly purified T lymphocytes to alpha 2M-trypsin complexes indicated that the effect was mediated through adherent cells. Addition of indomethacin did not modify the results. In the interleukin 2 (IL2)-dependent stimulation of purified T lymphocytes by anti-CD3 the effect of alpha 2M-proteinase complexes was probably due to the digestion of IL 2 through remaining proteinase activity. As alpha 2M-proteinase complexes are formed at sites of inflammation, the multiple immunomodulatory effects of alpha 2M-proteinase complexes might contribute to the dysregulation of the immune system in inflammatory diseases.

Purification and characterization of alpha 1-thiol proteinase inhibitor and its identity with kinin- and fragment 1.2-free high molecular weight kininogen

1. alpha 1-Thiol proteinase inhibitor (alpha 1 TPI) purified from outdated human plasma was a glycoprotein with Mr 83,000 and was composed of heavy and light chains held together with a disulfide bond. 2. The data on amino acid composition, amino terminal sequence of the light chain and carboxyl terminal sequences of the heavy and light chains indicate that alpha 1 TPI is identical with kinin- and fragment 1.2-free HMW kininogen. 3. Purified human plasmin generated a derivative having the same molecular weight (Mr 83,000), same subunit structure (heavy and light chains) and same inhibitory capacity as alpha 1 TPI from HMW kininogen and kinin-free HMW kininogen. This indicated the possibility that alpha 1 TPI is derived from HMW kininogen by plasmin.

Neutral proteinases of the human intervertebral disc

Disc tissue consisting of pooled annuli fibrosus and nuclei pulposus from the cadaver of an adolescent aged 19 years was extracted with 4.0 M Gu-HCl. Proteins of low buoyant density (p less than or equal to 1.38 g/ml) containing the disc enzymes and inhibitors were separated from proteoglycans of high buoyant density (p greater than or equal to 1.50 g/ml) by density gradient ultracentrifugation. Sephadex G-75F gel chromatography followed by trypsin affinity chromatography was then used to resolve disc proteolytic and trypsin inhibitory activities. The results obtained were strongly suggestive of the presence of a high molecular weight zymogen which upon activation generated a population of smaller molecular weight proteinases. The disc proteinases obtained by this process showed similar properties in terms of: their pH optima (7.4-7.6); their inhibition patterns by class-specific proteinase inhibitors; their variation of activity as a function of NaCl and lysine concentrations; and the hydrodynamic size of their proteoglycan degradation products. The activated disc neutral proteinase demonstrated many characteristics in common with plasmin; however, unlike the latter, the disc proteinases also showed some calcium dependence.

Tissue plasminogen activator in avascular tissues of the eye: a quantitative study of its activity in the cornea, lens, and aqueous and vitreous humors of dog, calf, and monkey

We analysed the tissue plasminogen activator (TPA) content of the corneal epithelium, endothelium, and stroma and of the lens, as well as the aqueous and vitreous humors, in dog, calf, and monkey eyes. A quantitative estimation of the TPA activity in the corneal tissues by the [125I]fibrin-coated well assay showed similar levels of activity in the corneal epithelium, stroma, and endothelium. However, some differences were observed among the three mammalian species analysed. The values, expressed in urokinase (UK) units of activity per mg protein, ranged from 0.8 +/- 0.22 to 1.03 +/- 0.23 for the epithelium, 0.47 +/- 0.13 to 0.98 +/- 0.2 for the stroma, and 0.48 +/- 0.11 to 0.93 +/- 0.22 for the endothelium. The lens, the vitreous and the aqueous humor yielded low to negligible values. However, by using the enzyme-linked immunosorbent assay (ELISA) method, we detected an appreciable amount of TPA in the lens (9.49 +/- 1.5 ng TPA per ml lens), corneal epithelium (1.43 +/- 0.29 ng TPA per mg protein) and vitreous humor of the dog (5.71 +/- 0.61 ng TPA per ml vitreous humor) and of the calf (5.7 +/- 0.44 ng TPA per ml vitreous humor). Such discrepancies may reflect species-specific variation in the TPA content of the tissues and possibly the limitations of the techniques utilized, because of the problem related to cross-reactivity between the TPA of a given species and the antibody used in the assays.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasminogen interacts with human platelets through two distinct mechanisms

Glu-plasminogen, the native form of plasminogen, interacts in a specific and saturable manner with unstimulated human platelets, and the binding is enhanced fivefold by thrombin stimulation (Miles and Plow, 1985. J. Biol. Chem. 260:4303). This study characterizes the nature of the Glu-plasminogen binding sites by analyzing platelets deficient in selected proteins and functions. Platelets from patients with afibrinogenemia, Gray platelet syndrome, and the Cam Variant of thrombasthenia, a form of thrombasthenia with near normal levels of glycoprotein IIb/IIIa (GPIIb/IIIa), showed minimal augmentation of plasminogen binding to thrombin-stimulated platelets but normal binding to unstimulated platelets. This selective deficiency indicates that two distinct mechanisms are involved in the interaction of plasminogen with platelets. These abnormal platelets share a deficiency in fibrinogen. Surface expression of platelet fibrinogen, however, was not sufficient for enhanced plasminogen binding to stimulated platelets, and experiments with alpha-thrombin and gamma-thrombin indicated that fibrin formation on the platelet surface is necessary for the augmented plasminogen binding. Unstimulated and stimulated thrombasthenic platelets deficient in GPIIb/IIIa bound markedly reduced levels of plasminogen, which suggests a role for GPIIb/IIIa in plasminogen binding to unstimulated platelets. Treatment of platelets to dissociate the heterodimeric complex of GPIIb/IIIa did not significantly perturb plasminogen binding to unstimulated platelets, but the complex may be necessary for thrombin-stimulated plasminogen binding via its interaction with platelet fibrin.

Catalytic properties of human Lys77-plasmin. A comparative steady-state and pre-steady-state study

Values of kinetic parameters for the hydrolysis of esters and p-nitroanilides of L-lysine and L-arginine catalyzed by the Lys77 form of human plasmin (EC 3.4.21.7) have been determined between pH 5.5 and 8 (I = 0.1 M) at 21 +/- 0.5 degrees C. Over the whole pH range explored, Lys77-plasmin catalysis conforms to simple Michaelis-Menten kinetics, and steady-state and pre-steady-state data may be consistently fitted to the minimum three-step mechanism: E + S in equilibrium (k+1/k-1)E X S----(k+2)E X P + P1----(k+3)E + P2 In spite of the higher specificity of lysyl derivatives for Lys77-plasmin rather than the arginyl ones, kinetic parameters also depend on the nature of the N-alpha substituent and/or of the alcoholic or p-nitroanilidic moiety of the substrate. Among the esters and anilides considered, ZLysONp shows the most favourable kinetic parameters and may be the substrate of choice of Lys77-plasmin, in that it allows the determination of the enzyme concentration as low as 2 X 10(-9) M (about 1 X 10(-3) CU/ml), at the optimum pH value (approx. 8). Between pH 5.5 and 8, the pH profiles of kcat and kcat/Km for the Lys77-plasmin-catalyzed hydrolysis of ZLysONp and ZArgONp reflect the ionization of a single group (probably His-602 involved in the active site) with pKa values ranging between 6.4 and 6.6; at variance, values of Km are pH-independent.

Photoaffinity labeling of functionally different lysine-binding sites in human plasminogen and plasmin

Photoaffinity labeling of human plasmin using 4-azidobenzoylglycyl-L-lysine inhibits clot lysis activity, while the activity toward the active-site titrant, p-nitrophenyl-p'-guanidinobenzoate, or alpha-casein are maintained. Photoaffinity labeling of native Glu-plasminogen with the same reagent causes incorporation of approximately 1.5 mol label per mol plasminogen. This labeled plasminogen can be activated to plasmin by either urokinase or streptokinase. The resulting plasmin has full clot lysis activity and can be subsequently photoaffinity labeled with a loss of clot lysis activity. The rate of activation of labeled plasminogen by urokinase is increased relative to that of native plasminogen. epsilon-Aminocaproic acid blocks incorporation of photoaffinity label into both plasminogen and plasmin, indicating that the labeling is specific to the lysine-binding sites. The labels are located in the kringle 1+2+3 fragment in either photoaffinity-labeled plasminogen or plasmin. These results indicate that the specific lysine-binding site blocked in plasmin acts in concert with the active-site in binding and using fibrin as a substrate. This clot lysis regulating site is not available for labeling in plasminogen, but is exposed or changed upon activation to plasmin. The different lysine-binding sites labeled in plasminogen may regulate the conformation of the molecule as evidence by an enhanced rate of activation to plasmin.

Complete amino acid sequence of bovine plasminogen. Comparison with human plasminogen

The amino acid sequence of the single polypeptide chain of bovine plasminogen (786 residues, Mr 88092) was determined. Cleavage with CNBr yielded 13 fragments of which six originated from cleavage sites different from human plasminogen. Digestion with elastase gave three major fragments: kringles (1 + 2 + 3) and kringle 4, both with intact lysine binding sites, and mini-plasminogen. Subfragmentation was achieved mainly with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine (BNPS-skatole), Staphylococcus aureus V8 protease and trypsin. The sequences of fragments which were determined by automated Edman degradation, were aligned with overlapping sequences, or, in a few instances, by homology with the known sequence of human plasminogen. Sequence comparison with the human protein showed varying degrees of homology in the different functional and structural domains. The overall identity (78%) is practically the same as that found in those regions corresponding to the heavy (79%) and the light chain (80%) of plasmin. The average degree of identity among the kringles is 83%. Outside the kringle structures the extent of identity decreases, to 65% in the N-terminal region and to about 50% in the connecting strands between the kringles except for the strand between kringles 2 and 3, where only one out of 12 residues is exchanged. The results reported show that bovine plasminogen apparently contains the same structural and functional domains as human plasminogen. Bovine plasminogen also contains two carbohydrate moieties. The only partially substituted N-glycosidic site, Asn289, corresponds to partially glycosylated Asn288 in human plasminogen, whereas the O-glycosidic site of the human sequence, Thr345, is shifted to Ser339 in bovine plasminogen.

Determination of the complete amino-acid sequence of porcine miniplasminogen

The complete amino acid sequence of porcine miniplasminogen (Mr 37 600), comprising 341 residues, was determined by automated Edman degradation in a liquid-phase or solid-phase sequenator. Selected fragments were produced by cleavage with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine (BNPS-skatole), cyanogen bromide, hydroxylamine, Staphylococcus aureus protease or trypsin or with combinations thereof and by activation with urokinase. The sequence obtained was compared with the known sequences of human and bovine miniplasminogen, indicating that the porcine molecule apparently contains the same structural and functional domains as the protein of the other two species. Porcine miniplasminogen has a sequence homology of 83% with human and of 79% with bovine miniplasminogen; 74% of the amino acids are identical in all three species. The results show a higher degree of evolutionary conservatism in the structurally and/or functionally vital regions of the molecule (active site residues, kringle 5).

Recurring thromboembolic disease and pulmonary hypertension associated with severe hypoplasminogenemia

In a patient with pulmonary hypertension and a history of recurrent venous thrombosis, plasma concentrations of all known coagulant and inhibitor proteins were normal except for severe deficiency of plasminogen. Repeated analyses showed the circulating plasma plasminogen level to be 30% of normal by either functional or immunologic methods. We sought evidence for either increased activation of plasminogen or for dysplasminogen. There was no evidence for the former. Purified plasminogen studies disclosed a normal number of active sites and normal activation. Generated plasmin had normal catalytic activity. Isoelectric focusing disclosed normal distribution of isoforms. Affinity chromatography with lysine-sepharose showed the presence of the two variant forms; however, an increased proportion of the protein eluted in the first peak. Danazol administration induced an increase in circulating plasminogen, but the differences in affinity chromatography elution profile remained. We conclude that this patient has a deficiency of normally functioning plasminogen, probably due to decreased synthesis.

Transport of urokinase across the intestinal tract of normal human subjects with stimulation of synthesis and/or release of urokinase-type proteins

Oral administration of clinical-type high molecular weight urokinase (HMW-UK) in a single dose of 30,000-60,000 International Units (IU) in enteric-coated capsules, in a group of normal human subjects, induced a plasma fibrinolytic state suggesting transport of HMW-UK across the intestinal tract. Other groups of human subjects were given a single dose of 120,000 IU daily of pure HMW-UK for 1 d and 7 d together with a placebo dose, all of the ingredients except urokinase (UK), daily for 7 d. UK-type proteins were isolated from the plasma of blood samples drawn 6 h after administration of the final dose, by a sequential two-step affinity chromatography method first with [N alpha-(epsilon-aminocaproyl)-DL-homoarginine hexylester]-Sepharose and second with a specific rabbit anti-HMW-UK-IgG-Sepharose. The yield of UK-type proteins from the 7-d group, 0.79 mg/dl, was approximately twofold greater than that obtained from either the placebo or 1-d groups. The specific plasminogen activator activity of the 1-d and 7-d groups were similar, 508 and 537 IU/mg protein, respectively; negligible plasminogen activator activity could be detected in the placebo group. The kinetics of activation parameters of human Glu-plasminogen of the UK-type protein, isolated from the 1-d group, were similar to those obtained with urinary HMW-UK. The UK-type proteins isolated only from the 7-d group showed, in sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, a major protein band of molecular weight 53,000 in the same position as HMW-UK. In addition, two other major protein bands of approximately 140,000 and approximately 120,000 mol wt were found in the 7-d placebo-, and 1-d groups, and also in the 7-d group. The 53,000 mol wt protein, about 50% of the total protein in the 7-d group, was further purified by preparative SDS-polyacrylamide gel electrophoresis, and found to be a two-chain protein with a specific activity of 1,241 IU/mg protein. The protein showed common antigenic determinants with urinary HMW-UK. The oral administration of 120,000 IU HMW-UK to human subjects for 7 d stimulated the synthesis of a UK-type protein of 53,000 mol wt, probably the zymogen, from either the liver or vascular endothelium, which was released into the circulation, and converted into active UK by circulating plasmin. The induction of the fibrinolytic state produced the conversion of native circulating Glu-plasminogen into the degraded Lys-plasminogen form, which was found in large amounts in the plasma of the 7-d group. The new plasma components, e.g., the 53,000-mol wt UK-zymogen and Lys-plasminogen, could play an important role in clot resolution of the fibrin-thrombus in thromboembolic diseases. Oral administration of HMW-UK has been shown to be clinically effective in patients with cerebral thrombosis in a multicenter double blind study.

Cooperative association of plasminogen with fibrinogen

We have examined the association of both Glu- and Lys-plasminogen to fibrinogen by ultracentrifugal sedimentation equilibrium in neutral isotonic buffer in the presence of aprotinin. The fibrinogen and plasminogens, which were homogenous, did not exhibit any self-association. In each association study, five different molar ratios of plasminogen to fibrinogen were examined. The data were analyzed by mathematical modeling using nonlinear least-squares curve fitting. Analyses of molecular species present showed that up to 4 mol of either Glu- or Lys-plasminogen was associated with each mol of fibrinogen. For the binding of Glu-plasminogen, the values of the successive changes of the standard free energy of association were found to be -5.48, -7.73, -8.88, and -11.41 kcal/mol (Ka = 2.16 X 10(4), 1.32 X 10(6), 1.06 X 10(7), and 1.08 X 10(9) M-1). For the experimental conditions used here, the association of Lys-plasminogen appears to be described by virtually the same fitting parameters. The very marked cooperativity of association found here would appear to imply that there are significant alterations of the structure of fibrinogen as a result of each successive molecule of plasminogen bound.