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 nature of the receptors for T1 and T4 Neisseria gonorrhoeae on erythrocytes and other cells was investigated. In general, cells of nonprimate origin contained few receptors for gonococci. Receptors for T4 gonococci were only uncovered when host cells were pretreated with trypsin. Trypsinization, while unnecessary for T1 adherence to erythrocytes, enhanced attachment in inverse proportion to original erythrocyte sensitivity. Receptors for T1 and T4 organisms on trypsinized and trypsin-neuraminidase-treated erythrocytes were blocked by concanavalin A and peanut lectins, respectively, but a distinction could be made between them with wheat germ lectin and galactose oxidase. Of a number of sugars tested as inhibitors, only D-galactose blocked adherence of T4 but was without effect on T1. While the identity of erythrocyte receptors is uncertain, likely candidates are "band 3" protein and glycophorin, by virtue of their galactose content, lectin binding capacity, and partial exposure on the outer surface of the erythrocyte.
...
PMID:Some properties of the human erythrocyte receptors for Neisseria gonorrhoeae. 627 94

Vesicles were constituted with glycophorin, the Sendai virus receptor of human erythrocytes, and loaded with calcein, a polar derivative of fluorescein, at self-quenching concentrations. On exposure to Sendai virus and mild hypo-osmotic stress, vesicles of the appropriate composition released a significant portion of their internal contents, as indicated by an increase in calcein fluorescence. Susceptible liposomes were not induced to leak by heat-inactivated virus or by trypsin-treated virus. The response of the vesicles to virus attachment is thus analogous to virus-induced hemolysis and presumably involves fusion of the vesicle and virus membranes. In addition to glycophorin and phosphatidylcholine, cholesterol was absolutely required for the lytic response to the virus. The need for cholesterol was not attributable to inactivation of the virus by liposomes without cholesterol. The presence of gangliosides increased the encapsulated volume of the liposomes, but gangliosides did not effectively substitute for glycophorin. Thin-layer chromatography of lipid extracted from incubated virus and liposomes containing a small amount of a fluorescent phosphatidylcholine indicated that phosphatidylcholine in the vesicle is not chemically altered by functional interaction with the virus.
...
PMID:Sendai virus-mediated lysis of liposomes requires cholesterol. 630 Aug 60

The changes in water diffusion across human erythrocyte membrane following exposure to proteolytic enzymes and to p-chloromercuribenzene sulfonate (PCMBS) have been studied on isolated erythrocytes suspended in isotonic solutions. Trypsin digested glycophorin without significantly changing the pattern of other polypeptides in erythrocyte membrane. On the contrary, with chymotrypsin or papain an extensive digestion of band 3 protein occurred. No changes in water diffusion were noticed after exposure of erythrocytes to trypsin, chymotrypsin or papain. Neither trypsin nor chymotrypsin treatment prevented the inhibition of water diffusion induced by PCMBS. In contrast, exposure of erythrocytes to papain did hamper the inhibitory effect of subsequent incubation with PCMBS. Taking into account the degradation of band 3 protein by papain it appears that the binding site for PCMBS playing a role in the inhibition of water diffusion is located in this protein.
...
PMID:Water exchange through erythrocyte membranes. V. Incubation with papain prevents the P-chloromercuri-benzensulfonate inhibition of water diffusion studied by a nuclear magnetic resonance technique. 631 44

The major red cell sialoglycoproteins, the glycophorins, play a central role in the invasion of human red cells by Plasmodium falciparum. En(a-) cells deficient in glycophorin A (alpha) and S-s-U- cells deficient in glycophorin B (delta) are relatively resistant to invasion, while trypsin treatment of S-s-U- cells, which removes most of the remaining sialoglycoprotein, renders these cells almost totally resistant to invasion. Parasites inside these glycophorin-deficient cells develop normally. Invasion of erythroid precursors in vitro by merozoites of P. falciparum parallels the appearance of glycophorins on the surface of these nucleated cells, even though parasites fail to develop inside them. However, another type of cell from an erythroleukaemic line (K562) which expresses glycophorins on its surface is resistant to invasion. Furthermore, the observed increased invasion of young cells as opposed to an older cell population is not related quantitatively to the presence of glycophorins on the cell surface. Thus, although the role of glycophorins is both specific and important in the invasion of cells by P. falciparum, it is clearly only part of a complex process.
...
PMID:Glycophorins and red cell invasion by Plasmodium falciparum. 634 Oct 1

Proteolytic enzyme activity releasing sialo glycopeptides from 3H-labeled human erythrocyte ghosts was detected in cytotoxic (leukotoxic) culture supernatants from 9 of 12 Pasteurella haemolytica serotypes. Microcrystalline cellulose thin-layer chromatograms of radioactive water-soluble products showed the following two radioactive peaks: a high-mobility minor peak (Rf, 0.54 to 0.74), identified as sialic acid, and a low-mobility major peak (Rf, 0.18 to 0.21), partially characterized as a trichloroacetic acid-soluble, sialic acid-rich fragment with a molecular weight of greater than 3,500, not extractable by chloroform. The sialic acid content of this fragment after treatment with Clostridium perfringens neuraminidase was estimated to be 7.2 X 10(-2) mumol mg-1. The presence of neuraminidase as a separate activity in some culture supernatants was confirmed. It is considered to be responsible for the observed release of free sialic acid. Preliminary studies with the crude enzyme showed that it has a broad pH optimum around pH 7.0 and that activity is not affected by inhibitors of trypsin, chymotrypsin, thermolysin, thio and serine enzymes, nor by an inhibitor of neuraminidase, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. Activity was, however, inhibited by o-phenanthroline at a high concentration after prolonged treatment. The enzyme hydrolyzed glycophorin at a rate four times higher than the rate for casein. Free glycophorin inhibited the enzyme-induced release of radioactive products from 3H-labeled ghosts. It is speculated that the novel enzyme is a neutral protease, probably metal-dependent, with specificity for sialoglycopeptides. The possible relationship of this protease to the previously reported host species-specific leukotoxicity of P. haemolytica and its potential role in virulence is discussed.
...
PMID:Proteolysis of sialoglycoprotein by Pasteurella haemolytica cytotoxic culture supernatant. 635 4

Plasmodium falciparum merozoites recognize and attach to glycophorins, the surface sialoglycoproteins of human erythrocytes. The structural requirements for a merozoite binding site were studied with the use of two methods. In the first, certain glycophorins and their tryptic fragments were added directly to isolated merozoites prior to their addition to erythrocytes. Low concentrations (50 micrograms ml-1) of glycophorin A inhibited merozoite invasion. At higher concentrations a mixture of glycophorins A, B and C (GPS) (100 micrograms ml-1) and glycophorin B (200 micrograms ml-1) also inhibited invasion. GPS from Tn erythrocytes which lack both sialic acid and galactose residues was almost as effective as normal GPS in blocking invasion. None of the monosaccharides present on glycophorin, including N-acetylneuraminic acid, inhibited merozoite invasion. Erythrocytes treated with lectins were only partially resistant to invasion. These results indicated that the oligosaccharide side chains are not the major structural determinant of the merozoite binding site. Glycophorin A was cleaved by trypsin and the separated fragments added to merozoites. Only the external N-terminal tryptic fragment T1 and the trypsin resistant hydrophobic core, T6, showed some, but considerably less, inhibitory activity than the intact molecule. In the second approach, the binding of 125I-labeled GPS to isolated merozoites was determined. 125I-GPS binding was saturated at 0.23 micrograms for 10(9) merozoites and was competitively inhibited by unlabeled GPS but not by free sugars. Desialylated GPS bound almost to the same extent as the intact molecule.
...
PMID:Binding of glycophorins to Plasmodium falciparum merozoites. 636 23

The importance of the red cell membrane sialoglycoproteins in the invasion of P. falciparum merozoites has been assessed. Human erythrocytes deficient in glycophorin A (En(a-)cells) or B (S-s-U-, S-s-U+ cells) showed significant resistance to invasion. Treatment of normal erythrocytes with trypsin and chymotrypsin also reduced invasion. These results indicate that determinants carried on glycophorins A, B and C play an essential role in the successful invasion into human red cells. Sugar components present on glycophorin, in particular N-acetyl glucosamine and N-acetyl galactosamine, as shown by specific sugar and antibody inhibition studies, appear to act as important determinants for attachment to the erythrocyte. This implicates a protein(s) on the merozoite surface membrane which has the properties of a lectin.
...
PMID:Merozoites of P. falciparum require glycophorin for invasion into red cells. 637 Apr 71

Immunoglobulin G autoantibodies selectively bind to senescent human red blood cells (RBC) in situ and initiate their removal by phagocytosis. In this paper, we characterize the IgG binding receptor appearing on senescent RBC using glycophorin-enriched vesicles prepared by Triton X-100 extraction of young, middle-aged, and old RBC populations. These vesicles contain all known sialoglycoproteins and trace contaminants of other proteins. IgG binds predominantly to vesicles from old cells, as determined by both 125I-labeled protein A binding to IgG molecules and an erythrophagocytosis-inhibition assay. Addition of lipids does not alter IgG binding. Liposomes prepared from lipids of young and old cell fractions do not bind significant amounts of IgG. IgG binding is reduced following trypsin treatment of vesicles. The data suggest that the age-specific cell antigen is a protein which co-purifies with sialoglycoproteins, but is not identical with glycophorin. Since it is extracted predominantly from senescent cells, a chemical modification within the membrane may either form the age-specific cell antigen during aging or render it accessible during senescence.
...
PMID:An age-specific cell antigen is present on senescent human red blood cell membranes. A brief note. 645 84

Glycophorin, the major sialoglycoprotein from the human erythrocyte membrane, has been isolated and recombined with phosphatidylcholine and cholesterol. Sucrose density gradient analysis of the recombinants shows that it is possible not only to recombine this protein with phospholipid, but also with phospholipid-cholesterol mixtures. Surprisingly, by the same analysis, it was possible to make a recombinant with cholesterol and glycophorin, only, in the absence of added phospholipid. The accessibility of the protein to trypsin was ested in each of these recombinants. In all the recombinants which contained either phospholipid, or phospholipid and cholesterol, the protein was protected from extensive hydrolysis. This is consistent with closed vesicles and incorporation of the protein into the recombinant membrane. Extensive hydrolysis of the protein occurred in the cholesterol-glycophorin recombinant indicating some differences in structure. Freeze-fracture electron microscopy of the phospholipid and the phospholipid-cholesterol recombinants showed mostly unilamellar vesicles, 1000 to 5000 A in diameter. Intramembranous particles were observed on both fracture faces, and the fracture planes were those expected for phospholipid bilayers. The glycophorin-cholesterol recombinants also showed fracture planes consistent with bilayers, and revealed intramembranous particles. Pieces of membrane-like structures as well as apparent vesicular structures were observed. Finally in the recombinants of glycophorin with phospholipid and cholesterol, cholesterol is shown to reduce the population of the motionally restricted phospholipid headgroup environment, in proportion to the mole percent cholesterol content.
...
PMID:Incorporation of the human erythrocyte sialoglycoprotein into recombined membranes containing cholesterol. 672 89

The addition of Ca2+ to aqueous dispersions of cardiolipin triggers complete hexagonal (HII) phase formation at Ca2+/cardiolipin molar ratios greater than or equal to 1.0 as detected by 31PNMR and freeze-fracture electron microscopy. Incorporation of the integral membrane protein glycophorin prevents the bilayer leads to hexagonal (HII) phase transition at Ca2+/cardiolipin ratios as high as 15:1. Removal of the outwardly oriented, negatively charged sialic-acid-containing sugar groups of glycophorin with trypsin had little effect on the bilayer-stabilizing capacity of the protein. As the Ca2+ binding was found to be similar in both the cardiolipin and the cardiolipin-glycophorin systems, it can be concluded that the protein exerts a bilayer-stabilizing effect on the cardiolipin. In addition, the possibility that glycophorin may prevent vesicle fusion is also discussed.
...
PMID:The effect of an integral membrane protein on lipid polymorphism in the cardiolipin-Ca2+ system. 682 77


<< Previous 1 2 3 4 5 6 Next >>

---