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)

The mechanisms of invasion used by virulent and avirulent Salmonella choleraesuis were compared using a Vero cell invasion assay. Mouse virulent S. choleraesuis strain 38 and avirulent strain 9 were examined for their ability to invade and survive in Vero cells. The assay was performed by S. choleraesuis infection of the Vero cell monolayer alone and in the presence of various treatments applied to the Vero cell monolayers. Intracellular S. choleraesuis colony forming units were then counted to characterize the mechanism of bacterial uptake. Invasion was not affected by colchicine, but was significantly inhibited in the presence of cytochalasins B and D, chloroquine, and dansylcadaverine. Inhibition by the above substances suggested the importance of microfilaments and of receptor recycling in receptor mediated endocytosis. Both bacterial strains had decreased invasion in the presence of mannose and after enzymic treatment with trypsin. Mannose exposure caused a significant 48% decrease in the uptake of virulent S. choleraesuis 38 and a 28% decrease in avirulent S. choleraesuis 9. Inhibition of endosome acidification did not affect the virulent strain 38 as much as it affected avirulent strain 9. Results from these experiments suggested that Vero cell invasion by S. choleraesuis was due to host uptake by receptor mediated endocytosis, and was mediated in part by mannose-sensitive adhesins. Outer membrane proteins were extracted from the virulent and avirulent strain and compared using SDS-PAGE following surface protein labeling with 125I. Virulent S. choleraesuis 38 had a unique 35 kD protein. The outer membrane proteins of both strains were then examined by radio-immunoprecipitation and western blot using guinea pig polyclonal antisera and the 35 kD protein was again found to be unique to the virulent strain 38. Antisera against the 35 kD protein significantly inhibited invasion of Vero cells by S. choleraesuis strain 38.
...
PMID:A comparison of virulent and avirulent strains of Salmonella choleraesuis and their ability to invade Vero cell monolayers. 158 27

Various studies have shown that mannose receptors rapidly eliminate glycoproteins and microorganisms bearing high mannose-type carbohydrate chains from the blood circulation. The purpose of this study was to characterize the mannose receptor in the liver, which in vivo is involved in the rapid clearance of tissue-type plasminogen activator from the circulation. Human liver membranes were solubilized in Triton X-100, and the solution was applied to a tissue-type plasminogen activator Sepharose column. Bound proteins were eluted with ethylenediaminetetraacetate (10 mmol/L). A second, similar purification step rendered a single liver protein of 175,000 daltons. A combination of ligand blotting and a chromogenic assay for tissue-type plasminogen activator demonstrated that the identified liver protein is a mannose receptor because it bound tissue-type plasminogen activator, this tissue-type plasminogen activator binding being fully inhibited by 0.2 mol/L D-mannose. Western-blot analysis revealed that the isolated liver protein is immunologically identical to the human mannose receptor from placenta. Treatment of the liver protein and the placenta mannose receptor with trypsin yielded the same pattern of proteolytic degradation products as identified on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We conclude that the physiologically relevant mannose receptor for tissue-type plasminogen activator clearance isolated from human liver is immunologically and structurally similar to or identical with the human mannose receptor isolated from placenta.
...
PMID:Isolation and characterization of the mannose receptor from human liver potentially involved in the plasma clearance of tissue-type plasminogen activator. 161 83

The Type I isozyme of rat hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) is comprised of N- and C-terminal domains, associated with regulatory and catalytic functions, respectively. Extensive sequence similarity between the domains is consistent with evolution of the enzyme by gene duplication and fusion. Cleavage at tryptic sites located in the C-terminal domain is markedly sensitive to ligands present during digestion, while analogous sites in the N-terminal domain are either resistant to trypsin or unaffected by the presence of ligands. These results imply a lack of structural equivalence between the N- and C-terminal domains, with the overall structure of the N-terminal domain being "tighter" and with a major component of ligand-induced conformational changes being focused in the C-terminal domain. Based on a previously proposed structure for brain hexokinase, protection by substrate hexoses is attributed to substrate-induced closing of a cleft in the C-terminal domain. Similar protection at C-terminal cleavage sites results from binding of inhibitory hexose-6-phosphates to the N-terminal domain. In addition, hexose-6-phosphates evoke cleavage at a site, T5, located in a region that has been associated with binding of ATP to the C-terminal domain. Thus, alterations in this region, coupled with reduced accessibility resulting from cleft closure, may account for the mutually exclusive binding of inhibitory hexose-6-phosphates and substrate ATP. In the absence of Mg2+, all nucleoside triphosphates examined (ATP, UTP, CTP, and GTP) protected against digestion by trypsin. In contrast, ATP-Mg2+ stabilized the C-terminal domain but destabilized the N-terminal domain, while the chelated forms of the other nucleoside triphosphates were similar to the unchelated forms in their effect on proteolysis; the unique response to ATP-Mg2+ reflects the specificity for ATP as a substrate.
...
PMID:Effect of ligand binding on the tryptic digestion pattern of rat brain hexokinase: relationship of ligand-induced conformational changes to catalytic and regulatory functions. 192 35

Alpha-1-proteinase inhibitor (alpha-1-PI) was isolated from goat plasma by salt fractionation, and chromatography on a DEAE-cellulose column. The inhibitor was found to be homogeneous by gel chromatography, SDS-PAGE and PAGE.Mr values by gel filtration (57 kDa), and by SDS-PAGE (52 kDa), under reducing conditions were nearly the same suggesting that the inhibitor consists of a single polypeptide chain. It contained 13.8% neutral hexose but no sialic acid residue. The values of isoionic pH, and extinction coefficient at 278 nm were 4.84, and 4.6, respectively. Fluorescence spectral properties showed tryptophan residues in the inhibitor. Solvent perturbation difference spectra suggested 74% exposure of the tryptophan residues in the native molecule. Gel filtration behaviour of the inhibitor was consistent with a Stokes radius of 3.16 nm, diffusion coefficient of 7.02 X 10(-7) cm2-sec-1 and a frictional ratio of 1.24 suggesting asymmetry and/or excessive hydration of the inhibitor molecule. Goat alpha-1-PI, unlike human alpha-1-PI was found to be potent inhibitor of bovine trypsin but a poor inhibitor of porcine pancreatic elastase. It was virtually devoid of antichymotryptic activity.
...
PMID:Isolation and characterization of alpha-1-proteinase inhibitor from goat plasma. 193 Feb 50

A lectin was isolated from the homogenate of the tunicate Polyandrocarpa misakiensis by heat treatment, ammonium sulfate fractionation, gel filtration, and high-performance ion-exchange chromatography. Analytical gel filtration on Superose 12 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the lectin is a monomeric protein with a molecular mass of approximately 15 kDa. The lectin bound to an immobilized D-galactose column in the presence of calcium ion with a threshold of 500 microM and eluted completely with 5 mM EDTA. It did not bind to an immobilized D-mannose or N-acetyl-D-galactosamine column. Thus, Polyandrocarpa lectin was found to be a calcium-dependent galactose-binding lectin. The complete amino acid sequence of Polyandrocarpa lectin was determined by automated or manual Edman sequencing of the peptides derived by digestion with trypsin, endoproteinase Asp-N, Staphylococcus aureus V8 protease, and pepsin. It is composed of 125 residues, contains no carbohydrate group, and has a calculated molecular mass of 14,034 Da. The lectin contains four half-cystines, and Cys-21 and Cys-119 and also Cys-96 and Cys-111 form intrachain disulfide bridges, respectively. The amino acid sequence of Polyandrocarpa lectin shows about 20-30% homology with those of fly, barnacle, sea urchin, and several vertebrate lectins that belong to C-type lectin (Drickamer, K. (1988) J. Biol. Chem. 263, 9557-9560). Although the physiological role of Polyandrocarpa lectin is not clear, preliminary experiments suggest that the lectin may be related to defense mechanisms because it has a strong antibacterial activity.
...
PMID:A calcium-dependent galactose-binding lectin from the tunicate Polyandrocarpa misakiensis. Isolation, characterization, and amino acid sequence. 229 29

Mg2(+)-chelates of several nucleoside triphosphates were shown to increase the inactivation of rat brain hexokinase (ATP:D-hexose-6-phosphotransferase, EC 2.7.1.1) by 0.6 M guanidine hydrochloride, with ATP-Mg2+ having the greatest effect; unchelated forms did not significantly affect inactivation. Since catalytic activity has been associated with the C-terminal half of the molecule, these results were interpreted as indicating a destabilization of this C-terminal region by binding of these chelates to the substrate nucleotide sites, with the particular effectiveness of ATP-Mg2+ reflecting the specificity for this species as a phosphoryl donor. These compounds were also shown to bind to the N-terminal half of the enzyme, as judged by their ability to protect against denaturation by guanidine hydrochloride and subsequent digestion with trypsin. Both free and Mg2(+)-chelated forms afforded protection, with the unchelated nucleotides being most effective; a preference for ATP was seen only with the chelated forms. Thus, it was concluded that the N-terminal half of hexokinase contains a relatively nonspecific nucleotide binding site, distinct from the substrate nucleotide site previously shown to reside in the C-terminal half. On the basis of this same ability to protect the N-terminal half against denaturation and proteolysis, several other polyanionic ligands were shown to bind to this region of the molecule. These included inorganic phosphate, its analogs, sulfate and arsenate, and its homologs, pyrophosphate and tripolyphosphate. All of these anionic ligands were also shown to antagonize inhibition by the glucose 6-phosphate (Glc-6-P) analog, 1,5-anhydroglucitol 6-phosphate. The allosteric site for binding of Glc-6-P has previously been shown to reside in the N-terminal half of the molecule, and it is suggested that the antagonism of inhibition by Glc-6-P (or its analog) by these anionic ligands results from interaction with an anion binding site for which the 6-phosphate group of inhibitory hexose 6-phosphates must compete. A model depicting possible relationships between ligand binding sites on brain hexokinase, and how their interactions might lead to observed regulatory properties, is developed based on these and previous studies of ligand binding as well as evidence that mammalian hexokinases (Mr 100,000) have evolved by duplication and fusion of a gene coding for an ancestral hexokinase with Mr 50,000 and which, like the mammalian enzyme, was sensitive to inhibition by Glc-6-P.
...
PMID:Binding of nucleoside triphosphates, inorganic phosphate, and other polyanionic ligands to the N-terminal region of rat brain hexokinase: relationship to regulation of hexokinase activity by antagonistic interactions between glucose 6-phosphate and inorganic phosphate. 230 21

Although antigen-reactive T lymphocytes play a central role in the host response to Histoplasma capsulatum, little is known of the nature of Histoplasma antigens recognized by these cells in vitro. Employing a murine T-cell line and two clones that are reactive with histoplasmin, we examined whether activation of T cells by histoplasmin required the presence of carbohydrate or protein moieties. The approach taken was to modify carbohydrate or protein molecules in histoplasmin by chemical or enzymatic digestion or by lectin adsorption. In parallel, antigen was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis to correlate alterations in functional activity with changes in the electrophoretic appearance of histoplasmin. Treatment of histoplasmin with periodate (0.1 M, 0.05 M, and 0.01 M) or with the endoglycosidases N-glycanase and endoglycosidase H sharply diminished the capacity of histoplasmin to trigger responses by T cells. Reactivity of T cells to histoplasmin that had been adsorbed with lectins binding mannose, glucose, or galactose was reduced by greater than 70%; conversely, the responses by T cells to antigen that had been adsorbed with lectins specific for fucose, N-acetylgalactosamine, or N-acetylglucosamine ranged from 82 to 91% of that to control antigen. Proliferative responses by T cells to histoplasmin that had been digested with chymotrypsin, protease, or trypsin were 2 to 43% of control values. The electrophoretic appearance of histoplasmin was modified by some but not all of the treatments. Partially purified H and M antigens triggered proliferation of T cells. Thus, both carbohydrates and proteins must be present to induce optimal responses by T cells. A portion of the carbohydrates is N linked to proteins, and alpha-D-mannose (or alpha-D-glucose) and beta-D-galactose are the sugar ligands of carbohydrate-containing antigens.
...
PMID:Characterization of antigenic determinants in histoplasmin that stimulate Histoplasma capsulatum-reactive T cells in vitro. 245 54

The possible involvement of a 15-kDa phosphotyrosyl protein, pp15, in insulin action was investigated by using the insulin-mimetic agent, vanadate. Vanadate, a phosphotyrosine phosphatase inhibitor, was found to mimic insulin in 3T3-L1 adipocytes by three criteria. First, kinetic and concentration-dependence studies verified the insulin-like effect of vanadate in activating 2-deoxyglucose uptake. Insulin had an additive activating effect at a submaximal vanadate concentration, but showed no further activation at a saturating vanadate concentration. The trivalent arsenical, phenylarsine oxide (PAO) which forms complexes with vicinal dithiols, markedly inhibited vanadate-activated hexose transport in agreement with our previous studies in which PAO abolished the insulin-activated component of sugar uptake. Second, in situ phosphorylation experiments showed that vanadate activated tyrosine phosphorylation of the insulin receptor's beta-subunit. Exposure of vanadate-treated cells to PAO further increased the level of beta-subunit phosphorylation. The increased level of phosphorylation in the presence of PAO occurred only on tyrosyl residues. Third, vanadate caused the accumulation of a phosphorylated 15-kDa protein in the presence of PAO, but not in its absence. The characteristics of this protein were identical to those of pp15: 1) both proteins behaved identically by two-dimensional gel electrophoresis, 2) digestion of both proteins with trypsin gave rise to apparently identical phosphopeptides, and 3) both proteins contained phosphotyrosine as the only phosphoamino acid. The results indicate that both vanadate and insulin stimulate the accumulation of pp15 in the presence of PAO. The dithiol,2,3-dimercaptopropanol, but not a monothiol, reversed the effects of PAO on the inhibition of vanadate-induced hexose transport and the accumulation of pp15, thus implicating a vicinal dithiol in these actions of vanadate and insulin. Our results support the hypothesis that turnover of the phosphoryl group of pp15, a product of insulin receptor tyrosine kinase action, is coupled to signal transmission to the glucose transport system.
...
PMID:Effect of vanadate on the cellular accumulation of pp15, an apparent product of insulin receptor tyrosine kinase action. 245 50

We have studied the differential susceptibility to N-glycanase (peptide-N4-[N-acetyl-beta-glucosaminyl]asparagine amidase) of oligosaccharides at the individual glycosylation sites of mouse TSH and free alpha-subunits. Mouse thyrotropic tumor tissue or hypothyroid pituitary tissue were incubated with D-[2-3H]mannose for 6 h. [3H]Mannose-labeled TSH or free alpha-subunits were obtained from homogenates using specific antisera and were digested with N-glycanase in their native state or after heat denaturation and reduction in the absence or presence of detergents. Tryptic fragments of the digestion products were then analyzed by reverse phase HPLC so that the effects of N-glycanase at the individual glycosylation sites could be determined. N-Glycanase treatment of native molecules did not cleave oligosaccharides efficiently at Asn56 of alpha-subunits and Asn23 of TSH beta, whereas oligosaccharides at Asn82 of alpha-subunits were more susceptible regardless of whether the alpha-subunits were combined with TSH beta. Heat denaturation, reduction, and the presence of detergents did not substantially increase the cleavage by N-glycanase of the protected oligosaccharides, suggesting that the primary structures of the TSH subunits influenced efficiency at specific sites. Pretreatment of free alpha-subunits with trypsin failed to enable N-glycanase to work fully, as oligosaccharides at Asn56 were cleaved less effectively than those at Asn82. Thus, the susceptibility to N-glycanase differs at the individual glycosylation sites of mouse TSH and free alpha-subunits, and these differences may result from effects of the primary structures of the TSH subunits.
...
PMID:Differential susceptibility to N-glycanase at the individual glycosylation sites of mouse thyrotropin and free alpha-subunits. 245 9

The liver is frequently colonized by metastatic tumor cells despite its dense population of macrophages (Kupffer cells). We have studied the interactions between metastatic colon carcinoma cells (DHD) and syngeneic Kupffer cells under different experimental conditions in vitro. In an adhesion assay the binding of DHD cells to Kupffer cell monolayers was shown to be time and temperature dependent, reaching a maximum level after about 90 min of incubation at 37 degrees C. In contrast, only a low level of binding could be observed at 4 degrees C. The level of binding could be increased by pretreatment of the Kupffer cells with phorbol 12-myristate 13-acetate. A firm interaction between the two cell types was shown to be dependent on the presence of calcium- and trypsin-sensitive structures on the surface of the Kupffer cells. Pretreatment of the macrophages with the cytoskeletal inhibitors colchicine and cytochalasin B was also found to reduce significantly the binding of tumor cells. This binding was also inhibited to a large extent by D-mannose and N-acetyl-D-galactosamine. The Kupffer cells were not cytotoxic against the colon carcinoma cells.
...
PMID:Binding of metastatic colon carcinoma cells to liver macrophages. 249 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---