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

---

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

Cultured thyroid cells accumulate the lipophilic cation triphenylmethylphosphonium, indicating that there is an electrical potential (interior negative) across the plasma membrane. Thyrotropin stimulates the uptake of the lipophilic cation 3-fold, and the proton conductor carbonylcyanide-m-chlorophenylhydrazone causes efflux of triphenylmethylphosphonium accumulated in the presence or absence of thyrotropin. The stimulatory effect of thyrotropin on triphenylmethylphosphonium accumulation is not mimicked by human chorionic gonadotropin, a glycoprotein hormone with a similar structure whose target organ is not the thyroid, and the effect is abolished if the thyrotropin-receptor activity of the cells is destroyed by treatment with trypsin. Analogous effects are observed with thyroid plasma membrane vesicles which are essentially devoid of mitochondrial and soluble enzyme activities. Triphenylmethylphosphonium uptake and stimulation by thyrotropin occurs when NaCl, KCl, or Tris.HCl concentration gradients are artifically imposed across the vesicle membrane ([salt](out) > [salt](in)). It seems likely, therefore, that triphenylmethylphosphonium uptake is driven by a chloride diffusion potential (interior negative) and that thyrotropin either increases the permeability of the membrane to anions or decreases its permeability to cations. Thyrotropin-stimulated triphenylmethylphosphonium uptake in the vesicle preparations reaches a quasi steady-state within 3 min; in contrast, thyrotropin-stimulated adenylate cyclase activity is negligible during this period of time, becomes measurable after about 4 min, and is optimal after 12-15 min. Thus, a primary mode of action of thyrotropin on the thyroid cell may be an alteration in the electrical potential across the plasma membrane. The relevance of this observation to the mechanism of action of other glycoprotein hormones, certain bacterial toxins, and interferon is discussed.
...
PMID:Effects of thyrotropin on the thyroid cell membrane: hyperpolarization induced by hormone-receptor interaction. 19 88

Human trophoblast isolation and cell culture procedures were examined to identify variables that enhance secretion of chorionic gonadotropin (HCG) in primary culture. Brief exposure of unminced first-trimester placental specimens to a solution of trypsin-EDTA-DNAse, and isolation of the dispersed cells after Ficoll-hypaque centrifugation yielded primary cultures that were high in HCG secretion and content of epithelial-like cells. The gradual decline in HCG level with time in monolayer culture in these presumptive trophoblast cells was retarded by treatment with theophylline and cyclic adenosine monophosphate. Exposure to methotrexate (MTX) did not increase HCG secretion in normal trophoblast cells, in contrast to a 5-fold stimulation by MTX in the JAR line of choriocarcinoma cells. Clusters of polygonal cells in primary culture progressively lost their capacity to secrete HCG and their epithelial-like morphology. However, they could be maintained as cell strains through approximately 15 passages over a period of 13 to 16 weeks.
...
PMID:Isolation of function human trophoblast cells and their partial characterization in primary cell culture. 20 65

Various serine proteases (e.g., trypsin, alpha-chymotrypsin, Pronase, and subtilisin) stimulate adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity in a membrane-enriched fraction of the rat ovary. Maximum stimulation is observed at protease concentrations ranging from 3 to 10 mug/ml. Higher protease concentrations inhibit ovarian adenylate cyclase in a dose-dependent manner. Protease stimulation causes a 6- to 8-fold increase in adenylate cyclase activity, which is comparable to the stimulation observed with human chorionic gonadotropin. Combinations of trypsin plus hormone or trypsin plus NaF stimulate ovarian adenylate cyclase activity to a greater extent than does any one of these alone. The mechanism of protease stimulation of adenylate cyclase involves limited proteolysis because zymogen precursors fail to activate the cyclase as does trypsin pretreated with trypsin inhibitors. Unlike cholera toxin, the serine protease stimulation is immediate (within the first 5 min) and requires no additional factors (e.g., NAD(+)). It is unlikely that protease stimulation of adenylate cyclase results from a proteolytic modification of the hormone receptor on the cell surface, because of the additive effects noted above and because protease stimulation is also observed in ovaries desensitized to hormone that lack this hormone receptor. Results with Lubrol-treated membranes also suggest that proteolytic enzymes do not directly activate the catalytic subunit of the cyclase or unmask new catalytic sites because the protease effect (like hormonal stimulation) is abolished by the detergent, whereas fluoride stimulation is enhanced. Other data suggest that serine protease and chorionic gonadotropin stimulation of adenylate cyclase result from activation of a membrane protease that then regulates adenylate cyclase in the ovary.
...
PMID:Proteolytic enzyme activation of rat ovarian adenylate cyclase. 27 Jul 17

Specific cell membrane receptors for interferon have been postulated based on a variety of different observations, such as the following: trypsin treatment of monkey-mouse hybrid cells preferentially destroys sensitivity to primate interferon (9); syngeneic mice immunized with human-mouse hybrid cells develop surface-directed antibodies, which only block antiviral action of human interferon (24); interferon covalently bound to Sepharose beads retains its antiviral activity despite the fact that diameters of the beads are several times those of the cells (1,10,19); cells challenged with polyl:C to produce interferon do not develop resistance to viral infection in the presence of interferon antiserum (30). Interferon has a strong and specific affinity for the carbohydrate side chain of cell membrane gangliosides. Preincubation of Sepharose-bound interferon with gangliosides inhibits antiviral activity in the following order of potency: GM2 greater than or equal to GTl greater than GMl greater than or equal to GDla (3). Derivatives of GM2 lacking either terminal N-acetyl-galactosamine or terminal N-acetyl-neuraminic acid are not (or very little) inhibitory; in addition, binding to gangliosides is reversed by N-acetyl-neuraminyl-lactose, the trisaccharide common to all gangliosides. These data clearly demonstrate interferon's specificity for the carbohydrate moiety of the ganglioside molecule (6). Phaeseolus vulgaris lectin, which blocks antiviral action of interferon (4), also prevents binding of interferon to ganglioside-Sepharose affinity columns (2). Many substances of known affinity for gangliosides likewise inhibit action of interferon. These include cholera (15) and tetanus toxins (2), thyrotropin (5,23) and human chorionic gonadotropin (5). Although a more general effect on the state of the membrane or on cellular metabolism by these substances cannot be ruled out, competition for interferon binding sites appears to be the most plausible explanation. Increased sensitivity of certain transformed cells to interferon upon uptake of exogenous gangliosides not only supports the concept that these glycolipids are involved in binding of interferon to the membrane, but furthermore points to the importance of interferon-ganglioside interaction for triggering of the antiviral response (29).
...
PMID:Membrane receptors for interferon. 35 55

To examine the relationship between pre-protein cleavage and nascent chain glycosylation placental mRNA was translated in a reconstituted ascites cell-free system containing microsomal membranes prepared from tunicamycin-treated or untreated ascites tumor cells. In the absence of membranes, first trimester RNA directed the synthesis of the pre-form of the alpha subunit of human chorionic gonadotropin, whereas, in the presence of normal membranes, first trimester RNA directed the synthesis of a glycosylated form of the alpha subunit. Cell-free lysates containing membranes derived from tunicamycin-treated cells synthesized an alpha subunit protein with little, if any, carbohydrate. This protein was apparently sequestered into membranes since it was resistant to the action of trypsin which was added after translation. The pre-peptide of the alpha subunit protein was removed by treated membranes as determined by amino acid sequence analyses. The non-glycosylated protein pre-placental lactogen was also cleaved to its mature form by tunicamycin membranes. These data strongly suggest that, in vitro, glycosylation is not obligatory for pre-protein cleavage and sequestration of these placental protein hormones.
...
PMID:Processing of placental peptide hormones synthesized in lysates containing membranes derived from tunicamycin-treated ascites tumor cells. 56 37

Monolayer cultures of human midterm and term placentae have been established following trypsin dispersion of placental minces. Maintenance of endocrine function was monitored by the concentrations of specific hormones in the culture media. At either gestational age the cultures 1) secret estradiol-17beta(1) and estrone (in a ratio of about 1:20) and aromatize 3H- or 14C-dehydroepiandrosterone sulfate and 14C-androstenedione, estrogen production being markedly enhanced by addition of dehydroepiandrosterone (10(-6)7) to the culture medium; 2) metabolize 3H-pregnenolone to progesterone and 14C-cortisol to cortisone; and 3) produce increasing amounts of chorionic gonadotropin and decreasing amounts of placental lactogen during the first week in culture. It is proposed that the model is highly suited to the study of factors affecting hormonogenesis by the human placenta whether they be of maternal or of fetal origin.
...
PMID:Short term culture of human midterm and term placenta: parameters of hormonogenesis. 60 61

Tumor cells and urine-voided cells from patients with invasive bladder carcinoma as well as from healthy patients were examined cytologically, ultrastructurally and immunocytochemically. The ultrastructure of tumor cells showed an abundant, dilated, rough endoplasmic reticulum in the form of membrane-bound vacuoles full of granular to fibrillar material located perinuclearly and/or paranuclearly. Some cells exhibited enlarged modified lysosomes containing sparce flocculent and particulate precipitate. Papanicolaou staining of these cells showed two basophilic cytoplasmic textures, one green glossy-patchy, perinuclearly and/or paranuclearly, well segregated from the other texture of peripheral hematoxylinophilic foamy cytoplasm, comparable to the cytologic features of cell cultures originating in invasive bladder carcinoma. PAS diastase showed double distribution and texture of the perinuclear glycosaminoglycans, a glossy accumulated mass and large granules. Glycosaminoglycan sacs similar to those of cell cultures were also present in tumor-dispersed cells. There was a nonspecific binding of antisera against lysozyme, human chorionic gonadotropin and alpha 1-trypsin in normal and tumor cells. Tumor cells and tissues were positive for alpha 1-chymotrypsin distributed perinuclearly and in large spheres. Normal cells lacked the above characteristics. The results indicate that it is feasible to use the aforementioned characteristics in conjunction with the existing bladder-cytologic criteria for malignancy as markers in urothelial cancer with regard to prognosis of superficial tumors with high malignant potential.
...
PMID:A cytologic, ultrastructural and immunocytochemical comparison of tumor cells and cell cultures originating in invasive bladder carcinoma. 137 23

Few experimental models have been used to investigate how proteins fold inside a cell. Using the formation of disulfide bonds as an index of conformational changes during protein folding, we have developed a unique system to determine the intracellular folding pathway of the beta subunit of human chorionic gonadotropin (hCG). Three folding intermediates of the beta subunit were purified from [35S]cysteine-labeled JAR choriocarcinoma cells by immunoprecipitation and by reverse-phase high performance liquid chromatography (HPLC). To identify unformed disulfide bonds, nonreduced folding intermediates were treated with trypsin to liberate non-disulfide-bound, [35S]cysteine-containing peptides from the disulfide-linked peptides. Released peptides were purified by HPLC and identified by amino acid sequencing. The amount of a peptide that was released indicated the extent of disulfide bond formation involving the cysteine in that peptide. Of the six disulfide bonds in hCG-beta, bonds 34-88 and 38-57 form first. The rate-limiting event of folding involves the formation of the S-S bonds between cysteines 23 and 72 and cysteines 9 and 90. Disulfide bond 93-100, the formation of which appears to be necessary for assembly with the alpha subunit of the hCG heterodimer, forms next. Finally, disulfide bond 26-110 forms after assembly with the alpha subunit, suggesting that completion of folding of the COOH terminus in the beta subunit occurs after assembly with the alpha subunit.
...
PMID:Intracellular folding pathway of human chorionic gonadotropin beta subunit. 157 25

The role of cyclic AMP in the regulation of lutropin (luteinizing hormone, LH) receptors has been investigated in cultured mouse tumour (MA10) Leydig cells. The LH receptors were quantified by measuring the binding of 125I-labelled human chorionic gonadotropin (hCG). LH (0.03 nM) in the presence of 1 mM-dibutyryl-cyclic AMP [(Bu)2cAMP] caused a 3-8-fold increase in subsequent 125I-hCG binding. (Bu)2cAMP (1 mM), cholera toxin (11.9 nM) and forskolin (1 microM) each caused a 2-4-fold increase in binding. In the presence of translation (cycloheximide) and transcription (actinomycin D) inhibitors, there was a loss of detectable binding sites. (Bu)2cAMP increased the rate of recovery of binding sites after trypsin treatment of MA10 cells, with a concomitant 2-fold increase in the level of binding sites. Under conditions where receptor levels were increased by 3-8-fold there was also a significant increase in pregnenolone production. It is concluded that LH and cyclic AMP have positive regulatory effects on LH receptors in MA10 cells by inducing the synthesis of new receptors. These induced receptors are functionally coupled to steroidogenesis.
...
PMID:Induction of lutropin receptors by lutropin and cyclic AMP in cultured mouse tumour (MA10) Leydig cells. 216 44

Nonporous, microparticulate, monodisperse silicas with particle diameters between 0.7 and 2.1 microns are introduced as stationary phases in high-performance affinity chromatography. The immobilization of m-aminophenylboronic acid, p-aminobenzamidine, tri-L-alanine, and concanavalin A onto these silicas was successfully achieved using 3-isothiocyanatopropyl-triethoxysilane as an activation reagent. Immobilized phenylboronic acid was applied to the isolation of nucleosides, nucleotides, and glycoprotein hormones such as bovine follicotropin and human chorionic gonadotropin, while immobilized benzamidine was employed for the isolation of the serine proteases thrombin and trypsin, immobilized tri-L-alanine for the separation of pig pancreatic elastase and human leukocyte elastase, and immobilized concanavalin A for the isolation of horseradish peroxidase. In all affinity chromatographic systems studied, the nonporous monodisperse silicas showed improved chromatographic performance compared to results obtained with porous silica supports using identical activation and immobilization procedures. Furthermore, frontal analysis was used as a method to evaluate the influence of experimental parameters on biological activity and accessible ligand densities. Only minor changes in bioactivity were found with the nonporous affinity supports, where accessibilities were typically higher than ca. 60%. The immobilization of affinity ligands onto porous supports as used in this and associated papers thus represents a successful general procedure for the preparation of stable matrices with fast kinetics for use in high-performance affinity chromatography.
...
PMID:High-performance liquid affinity chromatography with phenylboronic acid, benzamidine, tri-L-alanine, and concanavalin A immobilized on 3-isothiocyanatopropyltriethoxysilane-activated nonporous monodisperse silicas. 254 22


1 2 3 4 5 Next >>

---