Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two proteinases (2A and 2B) purified from the granular fraction of horse blood leucocytes degrade casein (Km values 12.8 and 6mg/ml respectively) with maximum activity at pH 7.4 and in the presence of 2m-urea. Urea-denatured haemoglobin, fibrinogen, albumin and resorcin/fuchsin-stained elastin are digested at a slower rate. The enzymes hydrolyse synthetic substrates of elastase, N-benzyloxycarbonyl-L-alanine 4-nitrophenyl ester (Km 0.114 and 0.178 mM) and N-acetyl-tri-L-alanine methyl ester (Km 5.55 and 0.98 mM), but they do not hydrolyse synthetic substrates of trypsin, chymotrypsin and thrombin. The examined proteinases are completely inhibited by 2 mM-di-isopropyl phosphorfluoridate and show a sensitivity to butyl and octyl isocyanates similar to that of pancreatic elastase. The pH-dependence of their photoinactivation in the presence of Rose Bengal indicates the presence of histidine in the active centre. Proteinase 2A rather insensitive to iodination by IC1 as is pancreatic elastase, whereas proteinase 2B is totally inactivated after incorporation of five iodine atoms per enzyme molecule.
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PMID:Substrate specificity and modifications of the active centre of elastase-like neutral proteinases from horse blood leucocytes. 0 9

Inactivation of alpha- and beta-thrombin by alpha 2-macroglobulin, by alpha 1-proteinase inhibitor and by antithrombin-III and heparin was studied. The amount of alpha- and beta-thrombin inactivated by antithrombin-III was proportional to the concentration of the inhibitor, but the inactivation rates of the two forms of thrombin were different. Heparin facilitated complex-formation between alpha-thrombin and antithrombin-III, whereas inactivation of beta-thrombin by antithrombin was only slightly influenced, even at a heparin concentration two orders of magnitude higher. alpha 2-Macroglobulin inhibited both alpha- and beta-thrombin activity similarly, i.e. the amount of alpha- and beta-thrombin inactivated as well as the rates of their inhibition were the same. alpha 1-Proteinase inhibitor also formed a complex with alpha- and beta-thrombin, similarly to antithrombin-III, although the inactivation of the enzyme needed high inhibitor concentration and long incubation time. These results suggest that the inactivation of beta-thrombin, if it occurs in the plasma, is also controlled by plasma inhibitors.
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PMID:Inactivation of alpha- and beta-thrombin by antithrombin-III, alpha 2-macroglobulin and alpha 1-proteinase inhibitor. 7 48

Both the clotting and esterase activities of thrombin are inhibited by alpha1-proteinase inhibitor (alpha1-antitrypsin). The inhibition is a time-and temperature-dependent reaction which is proportional to the molar ratio of thrombin to inhibitor. Both the active-site serine residue of thrombin and the reactive-site lysine residue of alpha1-proteinase inhibitor are involved. alpha1-Proteinase inhibitor forms a 1:1 complex with thrombin that is comparable with the complex formed with trypsin and other proteinases. Incubation of the inhibitor with excess of thrombin, however, results in inactivation of nearly all the enzyme, even though only as much complex is formed as alpha1-proteinase inhibitor present. A portion of the remaining thrombin apparently aggregates. These results suggest that the mechanism for inhibition of thrombin may not be exactly the same as for trypsin, which is inhibited only to the extent to which complex is formed.
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PMID:Inactivation of human thrombin in the presence of human alpha1-proteinase inhibitor. 108 57

1. Three distinct lines of evidence indicate that proteinases are involved in the growth of cultured animal cells. 2. Endogenous growth-related proteinases have been identified, and exogenous proteinases can also stimulate cell proliferation, probably by different mechanisms. In some cases, higher concentrations of proteinases are cytotoxic. 3. Proteinase inhibitors, not surprisingly, inhibit cell growth, but can also be mitogenic at sub-inhibitory concentrations. 4. There must, therefore, be at least three major cellular processes in which proteinases or proteinase inhibitors can operate to exert a direct effect on cell proliferation. 5. Details of one action of an exogenous proteinase, typified by thrombin and the thrombin receptor, are becoming clear at the molecular level, but thrombin probably activates at least two intracellular signalling systems, as well as acting as a growth inhibitor in some situations. 6. Much remains to be investigated in other examples.
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PMID:Proteinases and proteinase inhibitors as modulators of animal cell growth. 147 61

Previous work (Jones, R. (1987) Cell Biol. Int. Reports 11, 833 and Jones et al. (1988) Development 102, 781-792) has shown that sperm proacrosin (the zymogen form of the acrosomal proteinase acrosin, EC 3.4.21.10) has the capacity to recognize and bind sulphated polysaccharides and that this property is important for the initial stages of fertilization in mammals. To investigate whether this behaviour is specific to proacrosin, a variety of other proteinases (chymotrypsinogen, trypsinogen, thrombin, elastase, plasminogen, pepsin, Streptomyces griseus proteinase and V8 proteinase from Staphylococcus aureus) were immobilized on nitrocellulose and probed with [125I]fucoidin. Only chymotrypsinogen and trypsinogen retained significant amounts of the probe with Kd values of 1.4.10(-6) M and 3.0.10(-5) M, respectively. Proteinase inhibitors were ineffective as blocking agents suggesting that enzymic activity is not involved in recognition. However, the tertiary structure of the proteins is important, since cleavage of intramolecular disulphide bonds with 2-mercaptoethanol reduced binding by 50-60%. Competition experiments with a variety of mono- and polysaccharides suggest that the number and disposition of sulphate groups is critical for interaction with basic residues on the protein. It is concluded that, like proacrosin, chymotrypsinogen and trypsinogen are bifunctional proteins.
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PMID:Unusual fucoidin-binding properties of chymotrypsinogen and trypsinogen. 210 45

A previous report from our laboratory indicated that a proteinase inhibitor is produced by rabbit T lymphocytes. We now report that a human T cell line, C91/PL, produces a proteinase inhibitor which inhibits the enzymatic activity of trypsin and kallikrein. This newly identified proteinase inhibitor (LPI 1) did not inhibit the enzymatic activity of four other serine proteinases (thrombin, plasmin, chymotrypsin, or pancreatic elastase), a thiol proteinase (papain), or a carboxyl proteinase (pepsin). Active synthesis of LPI 1 by the C91/PL cell line was shown by the appearance of similar levels of inhibitory activity in sequential cell supernatants, lack of appearance of inhibitor in supernatants of cells killed by heat or sodium azide or of viable cells in the presence of cyclohexamide, and incorporation of a radiolabeled amino acid into newly synthesized inhibitor. Although both the inhibitor of rabbit origin and of human origin are proteins produced by T cells and have similar inhibitory specificity, important differences were observed: LPI 1 is sensitive to boiling and the two inhibitors migrate differently upon electrophoresis in substrate-containing polyacrylamide gel. Furthermore, LPI 1 was produced by a cell line of the T4 phenotype which had been established by in vitro viral transformation of human cord blood lymphocytes with HTLV 1 whereas the inhibitor of rabbit origin was produced by normal splenic T cells. Three other human T cell lines of the T4 phenotype, MOLT-13, KE-37, and HPB-ALL, from patients with acute lymphoblastic leukemia did not produce a proteinase inhibitor. Thus, the production of proteinase inhibitors does not appear to be a general characteristic of human T cell lines nor of the T4 subset. Proteinase inhibitors produced by T cells may have an immunoregulatory role in proteinase-mediated physiological processes.
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PMID:A serine proteinase inhibitor produced by an HTLV I virus-transformed human T lymphocyte line. 243 46

Antithrombin III (ATIII) clearance from blood occurs by redistribution into the extravascular compartment and by binding to the endothelial surface. When, however, ATIII reacts with a proteinase such as alpha-thrombin, the complex is rapidly cleared from the circulation (half-life is approximately five minutes) by a receptor present on hepatocytes. This receptor binds a number of other serine proteinase inhibitors that are members of the class designated as the "serpins." ATIII, alpha 1-proteinase inhibitor, heparin cofactor II, and alpha 1-antichymotrypsin proteinase complexes bind to the same hepatic receptor, now designated as serpin receptor 1. Proteinase complexes with alpha 2-antiplasmin, another member of the serpin class, do not bind to serpin receptor 1. Recent studies suggest that the specificity of the receptor for serpins may reside in the so-called D helix (nomenclature based on the structure of alpha 1-proteinase inhibitor). The presence of ATIII on the surface of endothelial cells offers a unique mechanism for regulating proteinases formed during coagulation. Since this ATIII is probably associated with heparin-like substances and exists in a high-affinity state, the inhibitor rapidly binds proteinases such as alpha-thrombin. Once the complex forms, its affinity for heparinoids is decreased compared with ATIII, allowing the complex to dissociate from the endothelial surface for rapid clearance by the liver.
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PMID:Serpin receptor 1: a hepatic receptor that mediates the clearance of antithrombin III-proteinase complexes. 255 99

The explosive nature of the coagulation cascade led many scientists to investigate how it is regulated. Proteinase inhibitors such as antithrombin III inhibit active proteases of the coagulation cascade. Cofactors such as factor Va and factor VIIIa are proteolytically inactivated by activated protein C. Protein C is activated by the thrombin-thrombomodulin complex on the endothelial cell surface. Thus, the independent actions of the proteinase inhibitor system and the thrombomodulin-protein C system complement each other to maintain regulation of blood coagulation. The thrombin binding site of thrombomodulin was identified to be the fifth and sixth repeats of the epidermal growth factor-like domain. The same binding template contains sufficient information to block the functions of thrombin as a procoagulant. However, additional repeats are required for the activation of protein C. Thrombomodulin is the first example which illustrates that the epidermal growth factor-like domain functions as a binding template for thrombin and as a switch to turn off the procoagulant activity of thrombin as well as to trigger the protein C anticoagulant pathway. Epidermal growth factor-like structures are found in many of the coagulation factors. Complex formation is a repeated theme not only in the blood coagulation cascade but also in the thrombomodulin-protein C anticoagulant pathway.
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PMID:The role of complex formation and epidermal growth factor-like domains in the regulation of blood coagulation by the thrombomodulin-protein C system. 256 Aug 86

Chromatography of Crotalus adamanteus venom on CM-Sepharose, Cibacron Blue-Sepharose and Phenyl-Sepharose, followed by gel filtration on Ultrogel AcA 44, has resulted in the isolation in homogeneous condition of a metalloproteinase active on casein and hide powder azure. The proteinase has an alkaline isoelectric point, and the trivial name proteinase B ('basic proteinase') is suggested to distinguish it from previously characterized C. admanteus metalloproteinases. Proteinase B is a single chain glycoprotein containing one free sulfhydryl group and having a molecular weight of 60,000. Proteinase B was inactivated by treatment with EDTA, but exposure to phenylmethylsulfonyl fluoride had no effect on proteolytic activity. Proteinase B lacked hemorrhagic activity and did not digest chromogenic substrates specific for thrombin, plasmin or plasma kallikrein.
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PMID:Purification and partial characterization of a high molecular weight metalloproteinase from the venom of Crotalus adamanteus (eastern diamondback rattlesnake). 391 94

The clearances of 125I-labeled alpha 1-proteinase inhibitor-trypsin, antithrombin III-thrombin and alpha 2-macroglobulin-methylamine (CH3NH2) were compared in our previously described mouse model. alpha 1-Proteinase inhibitor-trypsin cleared with a t 1/2 of 20 min, antithrombin III-thrombin of 7 min and 125I-labeled alpha 2-macroglobulin-methylamine of 2 min. Competition studies were performed to determine whether one or several pathways clear these three ligands. The clearance of 125I-labeled alpha 1-proteinase inhibitor-trypsin and 125I-labeled antithrombin III-thrombin was blocked by large molar excesses of either ligand, but not by alpha 2-macroglobulin-methylamine. The clearance of 125I-labeled alpha 2-macroglobulin-methylamine can be blocked by a large molar excesses of unlabeled alpha 2-macroglobulin-methylamine but not by alpha 1-proteinase inhibitor-trypsin. These studies demonstrate that the clearance of alpha 1-proteinase inhibitor-trypsin complexes is independent of alpha 2-macroglobulin-methylamine and utilizes the same pathway which is involved in the clearance of antithrombin III-thrombin complexes.
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PMID:In vivo catabolism of alpha 1-proteinase inhibitor-trypsin, antithrombin III-thrombin and alpha 2-macroglobulin-methylamine. 617 38


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