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)

Glycoproteins which mediate intercellular adhesion were studied by comparing the effects of trypsin and the neutral proteinase, Dispase, on human keratinocytes metabolically labelled with D-[1-14C]glucosamine or L-[1-3H]fucose. Whereas digestion of keratinocytes with trypsin/EDTA resulted in loss of both cell-substratum and intercellular adhesion, only cell-substratum adhesion was disrupted by incubation with Dispase. Analysis of the radiolabelled glycoproteins by polyacrylamide-gel electrophoresis revealed that a glycoprotein of Mr 126 000 was cleaved by trypsin/EDTA, but not by Dispase. Surface labelling of keratinocytes with galactose oxidase/NaB3H4 confirmed that this glycoprotein was exposed on the cell surface. Addition of lmM-Ca2+ prevented dispersion of keratinocytes by trypsin and concomitantly protected the glycoprotein of Mr 126 000 from digestion. These results indicate that this glycoprotein has an important role in mediating intercellular adhesion of keratinocytes.
...
PMID:Identification of an epidermal cell-adhesion glycoprotein. 391 31

The reaction between human platelet membrane glucosyl transferase and collagen has recently been proposed as the mechanism for pletelet-collagen adhesion. Collagen contains glucosyl-galactose and galactose side chains linked through the galactose to hydroxylysine. Oxidation of the 6-hydroxymethyl position of the galactosyl residue to aldehydes with galactose oxidase completely abolishes platelet aggregation. This enzymatic modification of collagen can be fully reversed by reduction of the aldehydes formed by NaBH(4) with complete restoration of platelet aggregating ability. Limited digestion with bacterial collagenase abolishes the ability of collagen to aggregate platelets. Removal of the N-terminal telopeptides from collagen with trypsin does not affect platelet aggregation. Tertiary structure of soluble collagen is essential for platelet aggregation. Normal collagen is less effective than lathyritic collagen, which contains only a small number of cross-links. The decreased number of aldehyde groups in the lathyritic collagen are not responsible for the increase in aggregating ability, since reduction with NaBH(4) does not alter platelet aggregation. These results suggest that integrity and accessibility of the galactose receptor site may be crucial for the formation of a ternary collagenenzyme-platelet membrane complex which must precede platelet aggregation.
...
PMID:Critical role of the carbohydrate side chains of collagen in platelet aggregation. 434 38

In an effort to elucidate the nature of the collagen-platelet interaction, the effects of collagen modification on platelet aggregation have been studied. We have shown that purified rat skin (salt) soluble collagen is effective at about 20 nM in mediating platelet aggregation in human platelet-rich plasma. This concentration is somewhat greater than that required of several skin insoluble collagens (ca. 10 nM). Both the alpha1(I) and alpha2 chains from rat skin soluble collagen produced platelet aggregation, but only at concentrations of about 13 muM and 55 muM, respectively. In contrast, heat-denatured collagen and chains (e.g., 65 muM alpha1(I) and 160 muM alpha2) failed to induce platelet aggregation and to inhibit platelet aggregation by native collagen. Glycopeptides were prepared from human skin insoluble collagen by extended digestion with bacterial collagenase and trypsin, and were purified by gel filtration into two classes. One class of higher molecular weight contained sialic acid, glucosamine, galactosamine, fucose, mannose, galactose, and glucose, and the other of lower molecular weight consisted primarily of a mixture of galactose and galactosyl-glucose units O-glycosidically linked to hydroxylysine-containing peptides. We found that, after the residual tryptic activity contaminating the higher molecular weight fraction was inhibited, neither of the glycopeptide classes produced nor inhibited native human skin insoluble collagen-mediated platelet aggregation at the highest concentration examined (ca. 1-2 mg glycopeptide per ml of platelet-rich plasma). Highly purified samples of the hydroxylysyl glycosides, hydroxylysylgalactose and hydroxylysylgalactosylglucose (Hyl-Gal and Hyl-Gal-Glc, respectively), were prepared from human urine and labeled at galactose using galactose oxidase followed by reduction with tritiated borohydride. Binding studies with platelet-rich plasma showed that, at concentrations greater than 50 nM, Hyl-Gal gives apparent binding to platelets, but there was no evidence of Hyl-Gal-Glc binding to platelets at concentrations up to 250 nM. At concentrations several hundredfold higher than the equivalents present in the minimum concentration of rat skin soluble collagen required for platelet aggregation, neither Hyl-Gal (at 29 muM) nor Hyl-Gal-Glc (at 18 muM) caused platelet aggregation or inhibited platelet aggregation by native collagen. Also, at a concentration of 85 muM (which represents a concentration about two thousandfold higher than the equivalents in the minimum concentration of soluble collagen required for platelet aggregation) the Gal-Glc-containing 36 residue rat skin soluble collagen alpha1(I)cyanogen bromide #5 peptide had no platelet aggregating or inhibiting activity. Modification of at least 90% of the rat skin soluble collagen carbohydrate by mild periodate oxidation had no effect on the platelet aggregating activity. Human skin insoluble collagen was reacted with periodate under the same conditions, and this had no demonstrable effect on its ability to induce platelet aggregation. This indicates that the normal carbohydrate side chains of these collagens are not required for the platelet interaction that produces the release of ADP and other metabolic constituents and leads to aggregation.Thus, collagen-platelet interactions appear to involve at least two distinct binding sites on the platelet plasma membrane. One is a protein binding site that activates platelet aggregation and has high specificity and affinity for the collagen triple-helical fold or perhaps even for a particular amino acid sequence in the triple helix.
...
PMID:Collagen-mediated platelet aggregation. Effects of collagen modification involving the protein and carbohydrate moieties. 435

By use of galactose oxidase (EC 1.1.3.9), followed by reduction with tritiated sodium borohydride, the surface structures of transformed 3T3 and NIL cells, under ordinary growth conditions, were characterized by (i) deletion of the normally existing glycoprotein label and (ii) appearance or increase of a new glycoprotein label. NIL cells had a galactoprotein label with molecular weight 200,000 that was deleted in NIL cells transformed by polyoma virus. 3T3 cells had a glycoprotein label with molecular weight of 30,000 that was lost after transformation. Glycoproteins of transformed 3T3 cells, with molecular weight 105,000, and those of transformed NIL cells, with molecular weight 85,000, were not labeled in normal confluent cells, but became labeled after trypsin treatment. The label in glycolipids was quantitatively different in normal and transformed cells. The labeling pattern in glycoprotein and glycolipids of transformed NIL and 3T3 cells became similar to that of nontransformed cells when contact responses of transformed cells became conspicuous when cells were cultured in the presence of dextran sulfate or dibutyryl cyclic adenosine monophosphate, or in medium in which glucose was replaced with galactose.
...
PMID:Altered growth behavior of malignant cells associated with changes in externally labeled glycoprotein and glycolipid. 435 66

We recently reported the isolation of a rat monoclonal antibody designated 2.4G2 (9) that is directed against the mouse trypsin-resistant Fc receptor (FcR) for IgG2b and IgG1 immune aggregates. We have now utilized the Fab fragment of 2.4G2 as an affinity reagent to purify FcR from the macrophage cell line J774 to apparent homogeneity. The antigen isolated from J774 cells consisted of two general types of polypeptides with broad electrophoretic mobilities of approximately 60,000 and 47,000 mol wt. Similar broad bands ranging from 47,000 to 70,000 mol wt were isolated from various FcR-bearing cell lines of B, T, and null lymphocyte, as well as of macrophage origin. J774 FcR was judged to be a glycoprotein based on the sensitivity of its isoelectric point to neuraminidase digestion, its labeling with galactose oxidase/NaB[3H4], and its binding to concanavalin A-Sepharose. In phosphate-buffered saline, the isolated protein formed large aggregates that were shown to retain FcR activity, albeit with a somewhat altered IgG subclass specificity. The FcR aglutinated erythrocytes that were coated with both IgG2b and IgG2a that did not otherwise hemagglutinate. In addition, iodinated FcR bound to Sephadex beads coated with rabbit IgG, mouse IgG1, IgG2b, and IgG2a, but not to beads coated with mouse IgG3 or rabbit F(ab')2 fragments. The binding of the purified receptor to all IgG classes was inhibited by the Fab fragments of 2.4G2. In contrast, the binding of IgG2a to intact macrophages was inhibited by 2.4G2 Fab by only 15%, whereas rabbit IgG immune aggregate binding was almost completely abolished.
...
PMID:Purificaton of a functional mouse Fc receptor through the use of a monoclonal antibody. 615 45

Inhibition by low-molecular-weight sugars of precipitin line formation between a polysaccharide (EF) excreted by Leishmania tropica subsp. major, Leishmania enriettii, and rabbit antileishmanial antibodies on double gel diffusion plates revealed that galactose residues, possibly as components of lactosyl groups, were the critical immunodominant sugars mediating antibody recognition of EF. The galactose residues of the EF of L. tropica subsp. major were specifically labeled with tritium via galactose oxidase and sodium boro[3H]hydride. The radioactive EF had an apparent molecular weight of about 85,000 on sodium dodecyl sulfate-polyacrylamide gels and was precipitated by antileishmanial antibodies as well as Ricinus communis lectins I and II (galactose specific). Lectins specific for glucose-mannose residues, fucose, N-acetylglucosamine, and N-acetylgalactosamine did not precipitate the labeled EF. Treatment of [3H]EF with proteolytic (trypsin, papain, protease) or glycosidic (alpha-amylase, beta-galactosidase) enzymes had no effect on either the electrophoretic pattern of the material or on its recognition by antileishmanial antibodies or R. communis lectin. This resistance to enzyme activity suggests that EF may be a useful marker for the presence of the parasite in vivo if it can be detected in minute quantities.
...
PMID:Identification of galactose as the immunodominant sugar of leishmanial excreted factor and subsequent labeling with galactose oxidase and sodium boro[3H]hydride. 617 74

Glycoproteins and proteoglycans synthesized by human keratinocytes in medium containing D-[1-14C]glucosamine were extracted and analysed by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. Extraction of the labelled keratinocytes with 0.5% Triton X-100 removed most of the glycoconjugates and left the cytoskeleton and nuclear residue adherent to the substratum. In addition to the cytoskeletal proteins, there was a relatively simple profile of glycoproteins and glycosaminoglycans associated with this adherent cytoskeleton. These consisted of eight glycoproteins in the mol.wt. range 99000-232000, five proteins in the keratin region (mol.wt. 42000-61000), hyaluronic acid and a sulphated glycosaminoglycan. Surface labelling of the keratinocytes with galactose oxidase (with or without neuraminidase)/KB3H4 revealed that many of the glycoproteins were exposed on the cell surface. The importance of the glycoproteins and proteoglycans in attaching the keratinocytes to the substratum was examined by studying their expression after incubation in medium containing tunicamycin and their degradation after digestion with trypsin and hyaluronidase. These studies, together with an examination of the glycoconjugates released by sequential extraction with 0.5% Triton X-100 followed by 0.2% sodium dodecyl sulphate, revealed that the glycoprotein of mol.wt. 232000 has an important role in mediating the attachment of keratinocytes to the substratum.
...
PMID:Glycoproteins and glycosaminoglycans synthesized by human keratinocytes in culture. Their role in cell-substratum adhesion. 619 5

Goat antibodies directed against a subset of the externally oriented plasma membrane glycoproteins of hepatoma tissue culture (HTC) cells were used to follow the metabolic fate of the membrane antigens and the specifically bound immunoglobulin molecules in this cell type in cultures. Analyses of the immunoprecipitates from cells labeled in situ with neuraminidase and galactose oxidase, followed by reduction with tritiated sodium borohydride, indicate that about 40% of the galactose-labeled plasma membrane glycoproteins are recognized by the antiserum. Fluorescent microscopic analyses of cells treated with fluorescein-conjugated immunoglobulins and analyses of trypsin accessibility indicate that probably all of the antibodies bound to the cell surface are patched and internalized within about 4 hr when the cells are subsequently cultured at 37 degrees C in the presence of rabbit anti-goat immunoglobulins. At the same time, the antigens are also interiorized. Analyses of the cellular localization of the interiorized antigens and antibodies by cell fractionation on Percoll gradients show that the immunoglobulins to the cell surface antigens and the antigens themselves migrate to the same region of the Percoll gradient as lysosomal hydrolases. Although the antibodies bind to the cell surface glycoproteins and bring about patching and interiorization, there is no effect on the degradation of the plasma membrane antigens labeled via the galactose oxidase/borohydride reduction method. Furthermore, the iodinated antibodies directed against these membrane glycoproteins behave in their turnover properties like membrane antigens; the cell-bound specific immunoglobulins have the same half-life as the membrane glycoproteins. When the cells that had been reacted with the goat antibodies to membrane glycoprotein were cultured in the presence of rabbit anti-goat immunoglobulins, degradation of the former antibodies was effectively decreased. Similar results were obtained with concanavalin A and antibodies directed against this plant lectin.
...
PMID:Metabolic fate of cell surface glycoproteins during immunoglobulin-induced internalization. 625 73

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

Certain properties of experimental pellicles formed by the adsorption of salivary components on hydroxyapatite surfaces change over time. To determine whether enzymes likely to be present in the oral environment could induce such changes, pellicles were treated with saliva which had been incubated for 18 h at 35 degrees C to promote the elaboration of microbial enzymes. This treatment markedly reduced the numbers of Streptococcus mutans MT3 and JBP and S. sanguis FC-1 and C5 cells which attached, but it had little or no effect on the attachment of S. mitis RE7, Actinomyces viscosus LY7 and CK-8, Bacteroides gingivalis 381, or B. melaninogenicus subsp. intermedius 581. Heating the incubated saliva at 60 degrees C for 30 min partially reduced its pellicle-modifying activity, whereas heating at 80 degrees C for 30 min or 100 degrees C for 15 min completely eliminated such activity. This indicated that the saliva contained heat-labile substances, presumably enzymes, which could affect the pellicle receptors involved in the attachment of S. mutans and S. sanguis. Treatment of saliva-treated hydroxyapatite with commercially obtained enzyme preparations also affected bacterial attachment. Thus, treatment with galactose oxidase reduced the numbers of the S. mutans strains which attached, whereas treatment with neuraminidase reduced the adsorption of S. sanguis FC-1 but not that of S. sanguis C5. Treatment with beta-glucosidase preparations derived from almonds significantly reduced the attachment of all of the streptococcal strains studied, but, when subjected to isoelectric fractionation, the adherence-inhibiting activity did not correlate directly with beta-glucosidase activity. Treatment of the pellicles with trypsin or eight other glycosidases did not affect streptococcal attachment. Exposure of the enzymatically modified pellicles to fresh saliva did not restore the streptococcal receptors. Collectively, the data suggest that some bacterial receptors in the pellicle coating of teeth can be modified by enzymes likely to be present in the oral environment, and these interactions may affect oral bacterial ecology.
...
PMID:Enzymatic modification of bacterial receptors on saliva-treated hydroxyapatite surfaces. 628 Nov 93


<< Previous 1 2 3 4 Next >>

---