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:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It was found that a non-tumorigenic epithelial cell line from the liver of a Buffalo-strain rat (BRL) secreted into the culture medium various inhibitors of the growth of BRL and RSV-BRL (tumorigenic BRL transformed by infection of Rous sarcoma virus). The secreted inhibitors were classified into two types: one inhibited the growth of BRL to a greater extent than that of RSV-BRL (non-tumorigenic BRL growth inhibitor, NGI), and the other, vice versa (tumorigenic BRL growth inhibitor, TGI). Two NGI (NGI-I and NGI-II) and two TGI (TGI-I and TGI-II) were highly purified from the serum-free conditioned medium. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis without 2-mercaptoethanol, NGI-I and II gave protein bands with molecular weights (Mr) of 56,000 and 21,000, respectively. TGI-I and II gave a band that migrated faster than bromophenol blue marker dye, but they did not pass through an ultrafiltration membrane with an Mr cutoff of 5,000. In the presence of a reducing reagent, only NGI-II showed a decrease of Mr, from 21,000 to 11,000. NGI and TGI showed 50% growth inhibition with BRL and RSV-BRL, respectively, at 5-15 ng/ml in the medium containing 10% fetal calf serum. NGI and TGI all were stable to 1 M acetic acid (pH 2.3) and 6 M urea, but labile to 5 mM dithiothreitol or trypsin. Of the eight cell lines tested, NGI-I was most effective on BRL, NGI-II on BRL and HSC-3 (human tongue squamous carcinoma), and both TGI-I and II on RSV-BRL.
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PMID:Multiple forms of growth inhibitors secreted from cultured rat liver cells: purification and characterization. 317 May 13

We have previously reported that in culture, rabbit serum inhibits the growth of the epithelial cell line from Buffalo rat liver (BRL) lower than that of the tumorigenic one transformed by Rous sarcoma virus (RSV-BRL). Here, the serum was fractionated by several different methods. The findings are: 1) the growth inhibitor present (GI) existed as large complexes with non-inhibitory proteins; 2) the complexes were dissociated by 1 M NaCl plus 6 M urea; 3) the dissociated GI did not pass through membrane filter with Mr cutoff 10k; 4) it was stable in 8.5 M urea and 1 M acetic acid (pH 2.5), but labile against either dithiothreitol and trypsin; 5) it was separable into two species with pI 7.5 and 9.5; 6) both species were more effective on RSV-BRL than on BRL.
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PMID:Growth-inhibitory protein present in rabbit serum, which is more effective on tumorigenic rat liver epithelial cells than on non-tumorigenic ones: its species, and mode of existence. 368 92

When monolayer Chinese hamster cells are treated with trypsin for short periods of time, ornithine decarboxylase (ODCase) activity increases two- to fourfold. This increase can be blocked by aprotinin, a protease inhibitor, and is not observed when cultures are dislodged from substrate mechanically prior to contact with exogenous trypsin. The trypsin-induced increase in ornithine decarboxylase activity is not due to degradation of enzyme or inhibitor molecules or to new enzyme synthesis. Immunoprecipitable protein, radiolabeled with [3H]alpha-difluoromethylornithine in vitro, is the same molecular weight in cells harvested with or without trypsin. Protein-bound levels of this specific enzyme-activated irreversible inhibitor of ornithine decarboxylase are unchanged by trypsin treatments that increase enzyme activity. Trypsin treatment of rat embryonic fibroblasts, transformed by a temperature-sensitive mutant of Rous sarcoma virus, increases ODCase activity in cells growing at the nonpermissive, but not at the permissive, temperature for the transformed phenotype. These results suggest that ornithine decarboxylase can be activated by exogenous trypsin treatment in a manner that is dependent on cell adhesion properties, which are modified in transformed cells.
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PMID:Activation of ornithine decarboxylase in monolayer cells treated with trypsin. 384 Aug 6

When stained with ruthenium red (RR), chick embryo cells infected with various strains of Rous sarcoma virus (RSV) and with avian leukosis viruses RAV-1 and RAV-3 showed an increase in the layer of acid mucopolysaccharides (AMPS) at their surfaces as compared with uninfected cells. This increase was most prominent in cells infected with the Fujinami strain of RSV. The layer was resistant to digestion with neuraminidase or trypsin but was readily removed by exposure to hyaluronidase. The thickness of this AMPS layer was not correlated with the varying degree of loss of contact inhibition exhibited by cells infected with the different strains of virus. The staining of the cell envelope with a solution of phosphotungstic and chromic acids (PTA-CR) suggested the presence of glycoproteins. The outer surface of the virions showed the same staining as the cell surface with RR and PTA-CR, and the budding virus particle was seen to incorporate the RR layer of the cell into its structure. The RR layers of cells and virions appeared to fuse, as did those between virus particles, suggesting that these layers play a role in the aggregation of virus particles and in their adherence to the surface of the cell.
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PMID:Ultrastructure of the surfaces of cells infected with avian leukosis-sarcoma viruses. 417 56

Glycopeptides were removed by trypsin digestion from the surface of control cells and cells transformed by Rous sarcoma virus, murine sarcoma virus, or polyoma virus. After digestion with pronase, the glycopeptides were analyzed by gel filtration. The elution profiles suggest that there are differences in the glycopeptides from the surface of control cells and those from transformed cells.
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PMID:Glycopeptides from the surface of control and virus-transformed cells. 432 50

Chick embryo fibroblast cultures develop fibrinolytic activity after transformation by Rous sarcoma virus (RSV). This fibrinolytic activity is not present in normal cultures, and it does not appear after infection with either nontransforming strains of avian leukosis viruses or cytocidal RNA and DNA viruses. In cultures infected with a temperature sensitive mutant of RSV the onset of fibrinolysis appears after exposure to permissive temperatures and precedes by a short interval the appearance of morphological evidence of transformation. See PDF for Structure The rate of fibrinolysis in transformed cultures depends on the nature of the serum that is present in the growth medium: some sera (e.g., monkey or chicken serum) promote high enzymatic activity, while others (calf, fetal bovine) do not. Some sera contain inhibitors of the fibrinolysin. Based on the effect of a small number of known inhibitors, at least one step of the fibrinolytic process shows specificity resembling that of trypsin. The sera of sarcoma-bearing chickens contain an inhibitor of the fibrinolysin, whereas normal chicken sera do not. For general discussion, conclusions, and summary see the accompanying paper, part II, (J. Exp. Med. 137:112).
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PMID:An enzymatic function associated with transformation of fibroblasts by oncogenic viruses. I. Chick embryo fibroblast cultures transformed by avian RNA tumor viruses. 434 90

The localization of a cell type-specific, soluble fibroblast surface antigen (SFA) was studied by immunofluorescence and by scanning electron microscopy of the same cells. The antigen had an uneven distribution forming streaks on chick embryo fibroblasts. It was localized to membrane processes and ridges, with a diameter of 50-200 nm. The processes extended from the periphery of the cells to the substratum or to other cells. Trypsin treatment completely removed detectable amounts of SFA. The antigen was detectable within 1 h after trypsin-treated cells were reseeded. The reappearance of SFA correlated with the restoration of membrane processes. Fibroblasts transformed by Rous sarcoma virus (RSV) showed loss of all or most SFA. When normal cells were transformed without subcultivation and trypsinization a fibrillar extracellular network of SFA remained under the transformed fibroblasts while the cells themselves were negative in immunofluorescence. When fibroblasts infected by RSV mutants were transferred to nonpermissive temperature for transformation new SFA was detected within 2 h. These data lead us to propose that loss of stabilizing and anchoring effect of SFA molecules in fibrillar cell surface structures may be critical in altered growth control and malignant transformation.
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PMID:Distribution of fibroblast surface antigen: association with fibrillar structures of normal cells and loss upon viral transformation. 437 93

A proteolytic activity is associated with structural protein p15 in avian RNA tumor viruses. Its effect on the known intracellular viral polyprotein precursors obtained by immunoprecipitation was investigated. Cleavage of Pr76gag resulted in the sequential appearance of p15, p27, and p19. The intracellular precursor Pr180gag-pol was also cleaved by p15, whereas the intracellular glycoprotein precursors of avian RNA tumor viruses, Pr92env, remained unaffected by p15 under all conditions tested. The specificities of the antibodies used to precipitate the precursors influenced the pattern of intermediates and cleavage products obtained by p15 treatment. If virus harvested from the the Prague strain of Rous sarcoma virus, subgroup C-transformed cells at 15-min intervals was incubated at 37 degrees C for further maturation, RNA-dependent DNA polymerase activity showed an optimum of DNA synthesis with 70S viral RNA or synthetic template-primers after short incubation periods. The presence of additional p15 during incubation resulted in a shift of the enzyme activity peak toward earlier time points. Virus harvested at 3-h intervals contained significant amounts of Pr180gag-pol and Pr76gag. The addition of p15 resulted in the cleavage of Pr180gag-pol and Pr76gag, but only a few distinct low-molecular-weight polypeptides appeared. Treatment of purified RNA-dependent DNA polymerase with p15 in vitro resulted in a disappearance of the beta subunit and an enrichment of the alpha subunit. In addition, a polypeptide of 32 x 10(3) molecular weight was generated. The cleavage pattern observed differed from the one obtained by trypsin treatment.
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PMID:Effect of p15-associated protease from an avian RNA tumor virus on avian virus-specific polyprotein precursors. 615 35

Conditioned media from Rous sarcoma virus transformed chicken embryo fibroblasts stimulate the uptake of 2-deoxyglucose in normal chicken fibroblasts. The factor responsible for this effect, which is also shed in very low amount by non-transformed fibroblasts, is destroyed by trypsin and not linked to the protease and plasminogen activator activities present in the media. Its apparent molecular weight, determined by gel filtration, is about 20,000 daltons. The factor released by transformed cells might be related to the monomeric form of a family of glucose binding and transport proteins recently reported by Lee and Lipmann ('78) to be detached by detergents from normal and transformed cells.
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PMID:Hexose uptake enhancing factor released from Rous sarcoma cells. 624 29

Normal and Rous sarcoma virus (RSV)-transformed chick embryo fibroblasts growing on plastic dishes were incubated with ATP (gamma 32P) in situ to detect external cell surface protein kinase activity. Under the conditions employed, 32P was incorporated exclusively into proteins, specifically those at the external cell surface, as radioactivity was removed by trypsin treatment of labeled whole cells. In addition, exogenous histones were phosphorylated when added to the reaction mixture. Cyclic nucleotides had virtually no effect on 32P incorporation, suggesting that little or no cyclic nucleotide-dependent protein kinase activity was present at the external cell surface. Cell surface protein kinase activity was higher in transformed than in normal cells, and, using a temperature-sensitive RSV src mutant, this difference was shown to be transformation-specific. Several differences were observed in the cell surface proteins phosphorylated in normal and transformed cells and at least two of these were transformation-specific. These data suggest that changes in external cell surface protein phosphorylation are associated with RSV transformation and thus could play a role in the formation of the transformed cell phenotype.
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PMID:External cell surface protein phosphorylation in normal and Rous sarcoma virus transformed chick embryo fibroblasts. 625 83


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