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:3.4.21.1 (chymotrypsin)
10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the plasmin-generating system, a serum component, in the development of dissociated embryonic chick spinal cord cells in culture was studied. Studies were performed in a defined system where the cells were maintained in a serum-free medium. Under these conditions the cells produce plasminogen activator. It was found that plasminogen, when added to the chemically defined culture medium at concentrations of 0.2-0.75 microgram/ml, stimulates [3H]thymidine uptake (as expressed per total DNA) in a dose-response manner. This mitogenic effect is abolished by the protease inhibitors leupeptin and aprotinin. Trypsin, but not chymotrypsin, can produce similar effects. It is concluded that plasmin, which is produced as a result of the activation of plasminogen, is a component that serves as a proliferation factor in developing spinal cords in culture.
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PMID:Role of the plasmin-generating system in the developing nervous tissue: I. Proteolysis as a mitogenic signal for the glial cells. 621 10

Previous studies in our laboratories (Miyata, T., et al. (1982) Proc. Natl. Acad. Sci. U.S. 79, 6132-6136) showed that the structural defect in a hereditarily abnormal plasminogen, plasminogen Tochigi, is due to replacement of Ala by Thr at position 600 from the NH2-terminal end. In the present studies, two abnormal plasminogens, plasminogens Tochigi II and Nagoya, obtained from other family members were analyzed to identify the structural impairment in these molecules. Amino acid sequence analysis of one of the tryptic peptides isolated, respectively, from plasminogens Tochigi II and Nagoya indicated that in both cases, Ala-600 (equivalent to Ala-55 of the chymotrypsin numbering system) had been replaced by Thr. No other substitutions at the active site and substrate-binding site residues, namely, His-57, Asp-102, Ser-195, and Asp-189, were found in the plasmin light chain variants, indicating that all these residues are intact. Moreover, the NH2-terminal heptapeptide sequences of the plasmin light chain variants isolated from plasminogens Tochigi II and Nagoya were identical to the sequence determined for the normal control. These results indicate that the absence of proteolytic activity of both abnormal molecules is due to the same amino acid substitution as that of previously reported plasminogen Tochigi.
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PMID:Plasminogens Tochigi II and Nagoya: two additional molecular defects with Ala-600----Thr replacement found in plasmin light chain variants. 623 49

The sequences of urokinase (UK) and tissue-type plasminogen activator (TPA) were aligned with those of chymotrypsin, trypsin, and elastase according to their 'structurally conserved regions'. In spite of its trypsin-like specificity UK was model-built on the basis of the chymotrypsin structure because of a corresponding disulfide pattern. The extra disulfide bond falls to cysteines 50 and 111d. Insertions can easily be accommodated at the surface. As they occur similarly in both, UK and TPA, a role in plasminogen recognition may be possible. Of the functional positions known to be involved in substrate or inhibitor binding, Asp 97, Lys 143 and Arg 217 (Leu in TPA) may contribute to plasminogen activating specificity. PTI binding may in part be impaired by structural differences at the edge of the binding pocket.
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PMID:Adaptation of plasminogen activator sequences to known protease structures. 634 97

Venom of the puff adder (Bitis arietans) contains a potent, basic, Mr 24,000 metalloproteinase activity that can destroy all detectable trypsin and chymotrypsin inhibitory activity, when venom is incubated with human plasma. We have found that during such incubation, concomitant activation of inactive renin occurs. In an examination of the mechanism involved we now report the activation, in addition, of plasma prekallikrein and serine proteinase activity, but not plasminogen, when human plasma is incubated with venom. Furthermore, venom was not able to release active trypsin from its complex with alpha 1-proteinase inhibitor and human renin was not inhibited by alpha 1-proteinase inhibitor. The activities in venom and venom/plasma mixtures were analysed using Sephacryl S-200 gel filtration and the effect of 10 mM EDTA and 5 mM phenylmethanesulphonyl fluoride on activities in column fractions was tested. The inactive-renin-activating, plasma prekallikrein-activating and serine proteinase-activating activities could be accounted for to a large extent by a venom metalloproteinase which was estimated to have a Mr of 24,000 by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis. This enzyme activity appeared to complex with alpha 2-macroglobulin when venom was mixed with plasma. Since both EDTA and phenylmethanesulphonyl fluoride could inhibit the activation of inactive renin by this metalloproteinase, it is suggested that the enzyme activates serine proteinase(s), which then activate inactive renin. Plasma kallikrein may have a role in this process. Additional peaks of inactive-renin-activating activity eluted from Sephacryl S-200 at Mr 30,000 and 80,000 (minor) and an additional, minor peak of caseinolytic activity eluted at Mr 60,000. The Mr 24,000 metalloproteinase in venom may have considerable utility in activating inactive renin at physiological pH owing to its ability to destroy plasma proteinase inhibitors at the same time.
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PMID:Mechanism of activation of inactive renin in human plasma by puff adder venom. 645 70

The entire amino acid sequence of complement factor B has been established combining both protein and DNA sequencing strategies. The zymogen consists of 739 amino acids, has four asparagine-linked carbohydrate sites, and has independently disulfide-bonded NH2- and COOH-terminal regions. The catalytic subunit, Bb, is a unique serine protease containing 259 amino acids that are not integral to any of the classical serine proteases. It is proposed that this region of the Bb fragment functions as a cofactor-binding domain for C3b. The Ba fragment was found to contain three regions of internal sequence homology which were unrelated to the "kringle" regions of prothrombin and plasminogen and which suggest an independent evolution for the B genome. Sequence alignment of the active site of B to the serine proteases was made using the three-dimensional structures of chymotrypsin and trypsin as molecular models. Three stretches within the hypothetical model for B contrast markedly with all known serine proteases in both amino acid sequences and predicted configuration. It is suggested that these "altered" regions contribute at least in part to the formation of the catalytic region of the C3 convertase.
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PMID:Complete primary structure for the zymogen of human complement factor B. 654 54

The complete amino acid sequences and the disulfide arrangements of the two chains of human haptoglobin 1-1 were established. The alpha 1 and beta chains of haptoglobin contain 83 and 245 residues, respectively. Comparison of the primary structure of haptoglobin with that of the chymotrypsinogen family of serine proteases revealed a significant degree of chemical similarity. The probability was less than 10(-5) that the chemical similarity of the beta chain of haptoglobin to the proteases was due to chance. The amino acid sequence of the beta chain of haptoglobin is 29--33% identical to bovine trypsin, bovine chymotrypsin, porcine elastase, human thrombin, or human plasmin. Comparison of haptoglobin alpha 1 chain to activation peptide regions of the zymogens revealed an identity of 25% to the fifth "kringle" region of the activation peptide of plasminogen. The probability was less than 0.014 that this similarity was due to chance. These results strongly indicate haptoglobin to be a homolog of the chymotrypsinogen family of serine proteases. Alignment of the beta-chain sequence of haptoglobin to the serine proteases is remarkably consistent except for an insertion of 16 residues in the region corresponding to the methionyl loop of the serine proteases. The active-site residues typical of the serine proteases, histidine-57 and serine-195, are replaced in haptoglobin by lysine and alanine, respectively; however, aspartic acid-102 and the trypsin specificity, residue, aspartic acid-189, do occur in haptoglobin. Haptoglobin and the serine proteases represent a striking example of homologous proteins with different biological functions.
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PMID:Covalent structure of human haptoglobin: a serine protease homolog. 699 77

By means of the method of ROLA & PUDLES modified by the authors the effect of trypsin and chymotrypsin inhibitors isolated from body walls of Ascaris lumbricoides on coagulation and fibrinolysis of human plasma in vitro was studied. The effect of both Ascaris inhibitors on coagulation phases I and II, the inhibition of thromboplastin and thrombin generations (thromboelastography, prothrombin and thrombin times) and the fibrinogenesis retardation of human plasma (time of lysis of euglobulin clot, time of clot fibrinolysis activated by streptokinase) were found. "The stairs phenomenon" was observed on thromboelastographic curves. The plasmin activity in an active form as well as its formation from plasminogen by streptokinase activation were reduced by chymotrypsin and trypsin Ascaris inhibitors alike.
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PMID:[Effect of proteolysis inhibitors from Ascaris lumbricoides on the coagulation and fibrinolysis of human plasma]. 712 86

Unlike most proteases, tissue-type plasminogen activator (t-PA) is secreted from cells as an active, single chain "proenzyme" whose catalytic efficiency is comparable with that of the corresponding mature, two-chain enzyme. We have previously suggested that the absence of the "zymogen triad" (Asp194-His40-Ser32; chymotrypsin numbering) contributes to this unusually high enzymatic activity of single chain t-PA. Consistent with this prediction, the single chain form of a variant of t-PA containing the zymogen triad displayed dramatically reduced activity toward synthetic substrates. Activation cleavage of this variant, however, resulted in a mature, two-chain enzyme with full catalytic activity. To further examine the functional significance of the zymogen triad, we used site-specific mutagenesis to construct a variant of t-PA, t-PA/R275E,A292S,F305H, that contained this triad but could not be converted into its two-chain form by plasmin. Characterization of this variant demonstrated that the presence of the zymogen triad specifically suppressed plasminogen activation by single chain t-PA in the absence of fibrin. In addition, these studies indicated that, like wild type t-PA, zymogen activation of this variant could be accomplished by binding to the co-factor fibrin. The combination of full activity in the presence of fibrin and reduced activity in its absence resulted in novel variants of t-PA that displayed dramatically enhanced stimulation by fibrin. While the presence of fibrin increased the catalytic efficiency of t-PA toward plasminogen by a factor of approximately 520, this stimulation factor increased to 130,000 for t-PA/R275E,A292S,F305H. Plasmin-resistant, zymogen-like variants of t-PA, therefore, may represent thrombolytic enzymes with enhanced "clot selectivity."
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PMID:Variants of tissue-type plasminogen activator which display substantially enhanced stimulation by fibrin. 762 53

The role of tumor suppressor proteins in the development of malignancy has made the understanding of their molecular mechanisms of action of great importance. Maspin is a tumor suppressor produced by a number of cell types of epithelial origin. Exogenous recombinant maspin has been shown to block the growth, motility, and invasiveness of breast tumor cell lines in vitro and in vivo. Although belonging to the the serine proteinase inhibitor (serpin) superfamily of proteins, the molecular mechanism of maspin is currently unknown. Here we show that the reactive site loop of maspin exists in an exposed conformation that does not require activation by cofactors. The reactive site loop of maspin, however, does not act as an inhibitor of proteinases such as chymotrypsin, elastase, plasmin, thrombin, and trypsin but rather as a substrate. Maspin is also unable to inhibit tissue and urokinase type plasminogen activators. Stability studies show that maspin cannot undergo the stressed-relaxed transition typical of proteinase-inhibitory serpins, and the protein is capable of spontaneous polymerization induced by changes in pH. It is likely, therefore, that maspin is structurally more closely related to ovalbumin and angiotensinogen, and its tumor suppressor activity is independent of a latent or intrinsic trypsin-like serine proteinase-inhibitory activity.
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PMID:The tumor suppressor maspin does not undergo the stressed to relaxed transition or inhibit trypsin-like serine proteases. Evidence that maspin is not a protease inhibitory serpin. 779 87

The agrin family of extracellular matrix proteins may be important in the formation of the neuromuscular junction. Using in situ hybridization with a probe recognizing all agrin isoforms, we demonstrate that it is widely expressed during mammalian embryogenesis. In the developing rat, particularly high levels of expression are found in the dorsal root and cranial ganglia, gut, whisker rudiments, penis, snout, teeth, retina, hippocampus, cerebral cortex and the lining of brain ventricles. Functional analysis of the recombinant rat protein shows that it is a potent inhibitor of the proteases trypsin, chymotrypsin and plasmin but not thrombin or the plasminogen activators. We conclude that agrin and its isoforms may play multiple roles in mammalian development including the regulation of proteolysis in the extracellular matrix.
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PMID:Isoforms of agrin are widely expressed in the developing rat and may function as protease inhibitors. 822 6


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