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)

The amino acid L-arginine is a precursor of endothelium derived relaxing factor (EDRF). The pentapeptide 6A (Ala-Arg-Pro-Ala-Lys) released by plasmin degradation of fibrinogen also contains arginine and relaxes vascular smooth muscle by releasing EDRF (nitric oxide). To determine and compare the effects of L-arginine, peptide 6A and a combination of L-arginine and peptide 6A on femoral artery blood flow and vascular resistance, anesthetized mongrel dog were administered saline, L-arginine, D-arginine, peptide 6A and L-arginine + peptide 6A in a random order. L-arginine and peptide 6A both induced an immediate dose-dependent short-lasting increase in femoral blood flow and a decrease in vascular resistance. Peptide 6A exerted a much greater (P less than 0.01) vasodilatory effect than did L-arginine at the same molar concentration suggesting that properties besides the arginine content are important in the effect of the pentapeptide. D-arginine had much less effect than L-arginine, indicating that the effect of L-arginine may be related to its utilization for synthesis of EDRF. When the peptide 6A was given soon after L-arginine, its effect on blood flow was not greater than that of L-arginine alone suggesting that L-arginine in a large amount makes guanylate cyclase less available for the more active peptide.
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PMID:Effect of L-arginine and an arginine-containing pentapeptide on canine femoral arterial blood flow. 177 15

We present evidence that over-expression of human plasminogen, the precursor to the serine protease plasmin, can be cytotoxic to mammalian cells. When an expression vector containing plasminogen cDNA is transfected into baby hamster kidney cells, the number of drug-resistant colonies as well as the levels of plasminogen secreted by those colonies is lower than observed in similar transfections of other protease precursor genes. The recombinant plasminogen accumulates intracellularly as degraded NH2-terminal fragments. In contrast, a mutant of plasminogen that produces inactive plasmin (active site Ser740 changed to Ala) is synthesized by these cells as a full-length plasminogen molecule, and the colony numbers and expression levels are normal. Thus, the generation of plasmin activity is responsible for the cytotoxic phenomena and the degradation associated with plasminogen expression. In addition, experiments using a plasminogen mutant that cannot be activated to plasmin (activation cleavage site Arg560 to Gly) or using coexpression of antisense urokinase RNA indicate that an endogenous plasminogen activator is responsible for converting newly synthesized plasminogen to plasmin. Finally, coexpression of plasminogen with alpha 2-plasmin inhibitor, a serpin which is the physiologic inhibitor of plasmin, prevents the toxic effects of intracellular plasmin activity and allows the synthesis and secretion of native human plasminogen.
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PMID:Expression of recombinant human plasminogen in mammalian cells is augmented by suppression of plasmin activity. 183 Dec 1

Plasmin generation by equimolar concentrations of tissue plasminogen activator (t-PA), pro-urokinase (pro-UK), and urokinase (UK), and a twofold higher concentration of a plasmin-resistant mutant rpro-UK (Ala-158-pro-UK) was measured on a microtiter plate reader. The promoting effects on this reaction of equimolar concentrations of fibrinogen, soluble fibrin (Desafib), CNBr fragment FCB-2 (an analogue of fragment D), or purified fragment E-2 were compared. Plasmin generation by t-PA was moderately promoted by fibrinogen, substantially promoted by Desafib and FCB-2, but not at all promoted by fragment E-2. By contrast, plasmin generation by pro-UK or by Ala-158-pro-UK was not promoted either by fibrinogen, Desafib, or FCB-2, but was significantly promoted by fragment E-2. Plasmin generation by UK was not significantly promoted by any of the fibrin(ogen) preparations. Treatment of fragment E-2 by carboxypeptidase-B (CPB), eliminated its promotion of pro-UK and Ala-158-pro-UK-induced plasmin generation. Pretreatment of FCB-2 with plasmin slightly potentiated its promotion of t-PA activity. This effect of plasmin pretreatment of FCB-2 was reversed by CPB treatment. Plasmin pretreatment of FCB-2 did not induce any promotion of activity in pro-UK or Ala-158-pro-UK. The findings show that the intrinsic activity of pro-UK and the activity of t-PA are promoted by different regions of the fibrin(ogen) molecule. The latter is stimulated primarily by a determinant in the fragment D region, which is available in intact fibrin. By contrast, plasminogen activation by the intrinsic activity of pro-UK was stimulated exclusively by fragment E-2, which is unavailable in intact fibrin. The findings are believed relevant to fibrinolysis and support the concept that t-PA and pro-UK are complementary, sequential, and synergistic in their actions.
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PMID:A comparative study of the promotion of tissue plasminogen activator and pro-urokinase-induced plasminogen activation by fragments D and E-2 of fibrin. 183 71

The mechanism of the activation of plasminogen by single-chain urokinase-type plasminogen activator (single-chain u-PA, scu-PA) was studied using rscu-PA-Glu158, a recombinant plasmin-resistant mutant of human scu-PA obtained by site-specific mutagenesis of Lys158 to Glu, and rPlg-Ala740, a recombinant human plasminogen in which the catalytic site is destroyed by mutagenesis of the active-site Ser740 to Ala. Conversion of 125I-labeled single-chain plasminogen to two-chain plasmin was quantitated on reduced sodium dodecyl sulfate-gel electrophoresis combined with autoradiography and radioisotope counting of gels bands. The efficiencies of both rscu-PA-Glu158 and rscu-PA for the activation of rPlg-Ala740 and of natural plasminogen were comparable and were 250-500-fold lower than that of recombinant two-chain u-PA (rtcu-PA) for rscu-PA-Glu158 and 100-200-fold lower for rscu-PA. Pretreatment of rscu-PA-Glu158 or rscu-PA with excess alpha 2-antiplasmin, which efficiently neutralizes all contaminating rtcu-PA, did not significantly reduce the catalytic efficiency of these single-chain moieties, indicating that they have a low but significant intrinsic plasminogen activating potential. The low intrinsic catalytic efficiency of rscu-PA for the conversion of plasminogen to plasmin may be sufficient to generate trace amounts of plasmin, which may regulate plasminogen activation by converting poorly active rscu-PA to very active rtcu-PA.
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PMID:Plasminogen activation with single-chain urokinase-type plasminogen activator (scu-PA). Studies with active site mutagenized plasminogen (Ser740----Ala) and plasmin-resistant scu-PA (Lys158----Glu). 196 15

Neutrophil-activating peptide 2 (NAP-2) is generated by cleavage of two inactive precursors, connective-tissue-activating peptide III (CTAP-III) and platelet basic protein (PBP), which are stored in the alpha-granules of blood platelets. Using highly purified CTAP-III as the substrate we studied the generation of NAP-2 by several neutral tissue proteinases. CTAP-III was rapidly cleaved by chymotrypsin, cathepsin G and trypsin, yielding products with neutrophil-stimulating activity. This activity remained unchanged for 24 h in the presence of chymotrypsin, decreased only slowly in the presence of cathepsin G, but was rapidly destroyed by trypsin. CTAP-III was also degraded by human neutrophil elastase and porcine pancreatic elastase, but no active fragments were obtained. By contrast, no degradation of CTAP-III was observed with thrombin, plasmin or 'granzymes' from cytolytic T-lymphocyte granules. Two active fragments of CTAP-III, generated by chymotrypsin or cathepsin G, were purified and partially sequenced, and were found to have the same N-terminal sequence as NAP-2. These results indicate that both proteinases cleave preferentially the bond between amino acids 15 (Tyr) and 16 (Ala) of CTAP-III. We conclude that chymotrypsin-like proteolytic activity in the vicinity of activated platelets may generate NAP-2 intravascularly. Due to its presence in the primary granules of neutrophils and monocytes cathepsin G is likely to be involved in this process.
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PMID:Formation of neutrophil-activating peptide 2 from platelet-derived connective-tissue-activating peptide III by different tissue proteinases. 203 37

The molecular interactions involved in the fibrin-mediated stimulation of plasminogen activation by tissue-type plasminogen activator (t-PA) were studied using natural human plasminogen (nPlg) and rPlg-Ala740, a recombinant human plasminogen in which the catalytic site is destroyed by mutagenesis of the active site Ser740 to Ala. Using this rPlg-Ala740 moiety, the dissociation constant of the interaction between plasminogen and CNBr-digested fibrinogen was determined to be 0.40 microM. In addition, conversion of 125I-labeled single chain plasminogen to two chain plasmin by single chain recombinant t-PA (rt-PA) in the absence or the presence of CNBr-digested fibrinogen was quantitated on reduced SDS-gel electrophoresis, combined with autoradiography and radioisotope counting of gel bands. In the absence of fibrin, the activation rate of nPlg and rPlg-Ala740 by single-chain rt-PA was comparable. In the presence of fibrin, however, the activation rate of rPlg-Ala740 was about 20-fold lower than that of nPlg. These results with rPlg-Ala740 may be explained by an impaired formation of the stable cyclic ternary complex between plasminogen, t-PA and fibrin, which mediates the fibrin stimulation of plasminogen activation by t-PA or, alternatively, by impaired conversion of single chain rt-PA to two chain rt-PA at the fibrin surface.
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PMID:On the molecular interactions between fibrin, tissue-type plasminogen activator and plasminogen. 210 98

The activation of plasminogen by t-PA was measured in the presence and absence of fibrin stimulation, using natural human plasminogen (nPlg) and rPlg-Ala740, a recombinant plasminogen with the active site Ser740 mutagenized to Ala. Recombinant wild type t-PA (rt-PA) was used as well as rt-PA-Glu275, a recombinant single chain t-PA in which the Arg of the plasmin sensitive Arg275-Ile276 peptide bond was substituted with Glu. Conversion of 125I-labeled single chain plasminogen to two-chain plasmin by wild-type or mutant t-PA, was quantitated by SDS gel electrophoresis and radioisotope counting of gel slices, and expressed as initial activation rates (v0 in pM s-1) per 1 nM enzyme. In the absence of fibrin stimulation, the v0 for the activation of nPlg and rPlg-Ala740 with the single chain forms of both t-PAs were comparable (0.6 to 2.7 pM s-1) but were lower than with the corresponding two-chain forms (5.3 to 23 pM s-1). In the presence of 1 microM soluble fibrin monomer (desAAfibrin), the v0 for nPlg and rPlg-Ala740 by single chain rt-PA was also comparable (24 and 33 pM s-1 respectively), whereas with 1 microM CNBr-digested fibrinogen, the v0 for nPlg with single chain rt-PA was about 20-fold higher than that of rPlg-Ala740 (135 and 7.5 pM s-1 respectively). In contrast, the v0 for nPlg and rPlg-Ala740 by single chain rt-PA-Glu275, two-chain rt-PA-Glu275 or two-chain rt-PA were comparable in the presence of either desAAfibrin or CNBr-digested fibrinogen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of fibrin-like stimulators on the activation of plasminogen by tissue-type plasminogen activator (t-PA)--studies with active site mutagenized plasminogen and plasmin resistant t-PA. 214 48

Increased extracellular proteolysis because of unregulated activation of blood coagulation, complement, and fibrinolysis is observed in thrombosis, shock, and inflammation. In the present study, we have examined whether the plasma kallikrein-kinin system, the classical pathway of complement, and the fibrinolytic system could be inhibited by alpha 1-antitrypsin reactive site mutants. Wild-type alpha 1-antitrypsin contains a Met residue at P1 (position 358), the central position of the reactive center. It did not inhibit plasma kallikrein, beta-factor XIIa, plasmin, tissue-type plasminogen activator (t-PA), or urokinase. In contrast, these serine proteases were inhibited by alpha 1-antitrypsin Arg358. For the inhibition of C1s, a double mutant having Arg358 and a Pro----Ala mutation at P2 (position 357) was required. This double modification was made because C1-inhibitor, the natural inhibitor of C1s, has Arg and Ala residues at positions P1 and P2. Plasminogen activator inhibitor 1, the natural inhibitor of t-PA, also has Arg and Ala residues at positions P1 and P2. In a purified system, alpha 1-antitrypsin Ala357-Arg358 was 150-fold less efficient against C1s than C1-inhibitor and 27,000-fold less efficient against t-PA than plasminogen activator inhibitor-1. In plasma, 2.3 microM alpha 1-antitrypsin Ala357-Arg358 reduced by 65% the formation of a complex between kallikrein and C1-inhibitor following activation of the intrinsic pathway of blood coagulation by kaolin. Furthermore, after supplementation by 2.0 microM alpha 1-antitrypsin Ala357-Arg358, zymographic analysis showed that the majority of the free t-PA of normal plasma formed a bimolecular complex with the double mutant. In contrast, 3.4 microM alpha 1-antitrypsin Ala357-Arg358 did not prevent the activation of the classical pathway of complement observed when normal serum is supplemented with anti-C1-inhibitor F(ab')2 fragment. These results demonstrate that alpha 1-antitrypsin Ala357-Arg358 has therapeutic potential for disorders with unregulated activation of the intrinsic pathway of blood coagulation and the fibrinolytic system; however, the double mutant is not an efficient inhibitor for the classical pathway of complement.
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PMID:Reactivity of alpha 1-antitrypsin mutants against proteolytic enzymes of the kallikrein-kinin, complement, and fibrinolytic systems. 219 58

Human rheumatoid synovial cells in culture secrete at least three related metalloproteinases that digest extracellular matrix macromolecules. One of them, termed matrix metalloproteinase 2 (MMP-2), has been purified as an inactive zymogen (proMMP-2). The final product is homogeneous on SDS/PAGE with Mr = 72,000 under reducing conditions. The NH2-terminal sequence of proMMP-2 is Ala-Pro-Ser-Pro-Ile-Ile-Lys-Phe-Pro-Gly-Asp-Val-Ala-Pro-Lys-Thr, which is identical to that of the so-called '72-kDa type IV collagenase/gelatinase'. The zymogen can be rapidly activated by 4-aminophenylmercuric acetate to an active form of MMP-2 with Mr = 67,000, and the new NH2-terminal generated is Tyr-Asn-Phe-Phe-Pro-Arg-Lys-Pro-Lys-Trp-Asp-Lys-Asn-Gln-Ile. However, following 4-aminophenylmercuric acetate activation, MMP-2 is gradually inactivated by autolysis. Nine endopeptidases (trypsin, chymotrypsin, plasmin, plasma kallikrein, thrombin, neutrophil elastase, cathepsin G, matrix metalloproteinase 3, and thermolysin) were tested for their abilities to activate proMMP-2, but none had this ability. This contrasts with the proteolytic activation of proMMP-1 (procollagenase) and proMMP-3 (prostromelysin). The optimal activity of MMP-2 against azocoll is around pH 8.5, but about 50% of activity is retained at pH 6.5. Enzymic activity is inhibited by EDTA, 1,10-phenanthroline or tissue inhibitor of metalloproteinases, but not by inhibitors of serine, cysteine or aspartic proteinases. MMP-2 digests gelatin, fibronectin, laminin, and collagen type V, and to a lesser extent type IV collagen, cartilage proteoglycan and elastin. Comparative studies on digestion of collagen types IV and V by MMP-2 and MMP-3 (stromelysin) indicate that MMP-3 degrades type IV collagen more readily than MMP-2, while MMP-2 digests type V collagen effectively. Biosynthetic studies of MMPs using cultured human rheumatoid synovial fibroblasts indicated that the production of both proMMP-1 and proMMP-3 is negligible but it is greatly enhanced by the treatment with rabbit-macrophage-conditioned medium, whereas the synthesis of proMMP-2 is constitutively expressed by these cells and is not significantly affected by the treatment. This suggests that the physiological and/or pathological role of MMP-2 and its site of action may be different from those of MMP-1 and MMP-3.
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PMID:Matrix metalloproteinase 2 from human rheumatoid synovial fibroblasts. Purification and activation of the precursor and enzymic properties. 226 96

When Glu-plasminogen (plg) was activated by urokinase (UK) in the presence of fibrinogen or fibrin, B beta peptides (B beta 1-42) were released faster from fibrinogen than from fibrin (B beta 15-42). These results were contrary to faster release of B beta 15-42 from fibrin in the UK-activated clotted plasma in comparison to the release of B beta 1-42 from UK-activated plasma. The addition of plasma or lysine-Sepharose pass through fraction to the above system resulted in faster release of B beta peptides from fibrin than fibrinogen. The addition of alpha 2 antiplasmin (alpha 2AP) to the mixture of Glu-pig, UK and fibrinogen or fibrin resulted in faster release of B beta peptides from fibrin than from fibrinogen. These results indicate that fibrin protected plasmin from inactivation by alpha 2AP, leading to cleavage of Arg(42)-Ala(43) bond in beta-chain of fibrin which seems to be less susceptible to plasmin than the same bond in fibrinogen.
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PMID:Release of B beta peptides from fibrinogen or fibrin in the presence of alpha 2 antiplasmin. 242 82


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