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)

A soluble lectin which agglutinates trypsin-treated rabbit erythrocytes was purified from calf heart using affinity chromatography on asialofetuin-Sepharose. Its molecular weight was determined by gel filtration to be approximately 17,000. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the predominant molecular species had a molecular weight of 9,000, suggesting that the lectin is a dimer. Binding studies performed with iodinated lectin revealed that neuraminidase-treated calf erythrocytes contained approximately 5 X 10(6) lectin binding sites per cell. Native calf and rabbit erythrocytes bound the lectin, but human and rat erythrocytes required neuraminidase and trypsin treatment, respectively, for lectin binding to occur. A number of saccharides, glycopeptides, and glycoproteins possess haptene inhibitory activity toward lectin binding to erythrocytes. The most potent of these have either galactose beta leads to galactose beta leads to, galactose beta N-acetylglucosamine beta leads to, or galactose beta leads to N-acetylglucosamine beta leads to sequences at their nonreducing termini. Lactose and galactose beta 1 leads to 3N-acetylgalactosamine are the next best haptenes. Finally, alpha-linked galactose residues and free galactose are very weak haptenes. The presences of a terminal sialic acid residue impairs haptene activity in all instances. Calf heart also contains a membrane-associated lectin which is very similar but not identical with the soluble lectin. A soluble beta-galactoside binding lectin was also isolated from calf lung. It has the same molecular size and subunit structure as the soluble heart lectin and is antigenically identical. In binding studies, the pattern of inhibition by various haptenes was the same for all three lectins.
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PMID:Isolation and properties of beta-galactoside binding lectins of calf heart and lung. 82 31

Agglutination studies with 6 plant lectins indicated that the unaltered surface coat of Trypanosoma equiperdum isolated from rat blood lacks the carbohydrate molecules preferentially bound by these proteins. However, trypsin, pronase, chymopapain, or papain treatments exposed the binding sites for Concanavalin A and the phytohemagglutinins M and P and trypsinized cells were attached to Concanavalin A immobilized on agarose beads. Lipolytic, amylytic, and other proteolytic enzymes or other agents did not reduce or induce lectin agglutination and wheat germ, Anti A, and Anti H lectins did not clump the trypanosomes under any of the conditions employed. Carbohydrate residues resembling D-mannose or n-acetyl-D-galactosamine are therefore within the surface coat of T. equiperdum or on the cell membrane underneath it. The results are contrasted with the lectin induced agglutination of other parasite species and mammalian cells.
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PMID:Lectin binding by trypanosoma equiperdum. 84 43

Three radioactive glycopeptides were isolated from human peripheral lymphocytes stimulated with Wistaria floribunda mitogen in the presence of D-[14C]glucosamine hydrochloride by mild trypsin digestion followed by gel filtration and preparative high-voltage paper electrophoresis. The carbohydrate compositions of these glycopeptides suggest that one has a sugar chain of the type found in serum glycoproteins, consisting of sialic acid, galactose, N-acetylglucosamine, mannose, and fucose in a molar ratio of 2:2:4:2:1, and the other two have sugar chains like those of mucins, consisting of sialic acid, galactose, and N-acetylgalactosamine in a molar ratio of 1 or 2:1:1. The results of enzymic degradation with purified glycosidases indicate that these sugar chains are similar in structure to their counterparts in human erythrocyte membranes.
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PMID:Isolation of glycopeptides from the lectin-stimulated human peripheral lymphocyte cell surface. 89 50

Rat glomerular basement membrane was extracted for 3 h with trypsin, pH 8.0. The supernatant solution was treated with trichloroacetic acid and the supernatant thus obtained was applied to Bio-Gel P200. The first of the two glycoprotein peaks was applied onto Sepharose derivatives of concanavalin A (Con A). Examination of the material retained by the unsolubilized Con A and subsequently eluted with methyl alpha-D-mannopyranoside reveals that the principal high affinity receptor for Con A is the renal glycoprotein, having antigenic activity that induces nephrotoxic antibody. This glycoprotein has also nephritogenicity (the activity capable of inducing glomerulonephritis in homologous animals by a single foot pad injection with Freund's incomplete adjuvant). Evidence is given to show that this binding is specific. The remainder of the renal glycoprotein is unretarded and is revealed to contain none of the activities described above. When fluorescein isothiocyanate-labelled Con A is, conversely, injected into rats through the renal artery, the specific binding of Con A to the glomerular capillary loop is proved. The results demonstrated appear to, indicate that the receptor for Con A present in normal rat glomerular basement membrane can be identified as the well-established chemical substance, the nephritogenoside, having the alpha-D-glucopyranosyl unit at the non-reducing terminus which is facing the endothelial aspects of the glomerular capillary loop.
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PMID:Nephritogenoside, the receptor glycoprotein for concanavalin A in rat glomerular basement membrane. Demonstration of alpha-D-glucopyranosyl unit at the non-reducing terminus. 91 92

Galactosyltransferase, which functions as the catalytic component of lactose synthase and in the glycosylation of glycoproteins, has been previously reported to have an absolute dependence on Mn2+ for activity, with a Kd for Mn2+ (10(-3) M) 2 to 3 orders of magnitude greater than the physiological range of Mn2+ concentrations (v 10(-6) M). Reinvestigation of the metal ion dependence of this enzyme has shown that Zn2+, Cd2+, Fe2+, Co2+, and Pr3+ also produce activation, although with lower activities at saturation than that attained with Mn2+. Velocity against metal ion concentration curves for all metals, including Mn2+, are sigmoid, suggesting the presence of two or more activating metal binding sites on the enzyme. The presence of two sites is confirmed by studies using both Mn2+ and Ca2+. While galactosyltransferase is inactive in the presence of Ca2+ alone, at low concentrations of Mn2+ (10(-5) M), enzyme activity is stimulated by Ca2+. A more detailed investigation by steady state kinetics has revealed that there is a tight binding site for Mn2+ (site I: Kd of 2 X 10(-6) M) from which Ca2+ is excluded, and a site at which Ca2+ can replace Mn2+ (site II: Kd for Ca2+ of 1.76 X 10(-3) M), to which metal binding has a specific synergistic effect on UDP-galactose binding, possibly as a result of the formation of an enzyme-Ca2+-UDP-galactose bridge complex. The site I Mn2+, site II Ca2+-activated enzyme has a maximum velocity similar to that of the Mn2+-activated enzyme, and is the enzyme form that must act in lactose synthesis in vivo. A trypsin-degraded form of galactose transferase (galactosyltransferase-T) (Powell, J.T., and Brew, K. (1974) Eur. J. Biochem. 48, 217-228) appears to lack site I and is activated by Ca2+ in the absence of Mn2+.
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PMID:Metal ion activation of galactosyltransferase. 93 1

Pretreatment of sheep erythrocytes with trypsin abolishes their specific binding and rosette formation with human T lymphocytes. A glycopeptide containing sialic acid is released from the intact sheep erythrocytes by incubation with trypsin and purified. This glycopeptide contains activity that can be bound to T lymphocytes and produces inhibition of rosette formation. This component with a m.w. of about 10,000 contains galactose, acetylglucosamine, acetylgalactosamine, sialic acid, and serine. These results suggest that the glycopeptide released by trypsin treatment may contain the site of the T cell receptor of sheep erythrocytes.
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PMID:Studies on glycopeptide released by trypsin from sheep erythrocytes. 93 29

Living Trypanosoma musculi bloodstream trypomastigotes were agglutinated specifically with concanavalin A (ConA), wheat germ agglutinin (WGA), soybean agglutinin (SBA), and fucose-binding protein (FBP). The agglutination with these lectins of living cells from which the coat was removed by trypsinization was the same as with intact trypanosomes. Glutaraldehyde or formalin fixation did not affect the results with regard to agglutination with WGA, SBA, and FBP, but lower agglutination with ConA was observed upon fixation. By using a dense iron-dextran marker many fewer ConA marker particles were localized at the fine structural level in the intact than in trypsin-treated trypanosomes. On the basis of the results obtained by agglutination and electron microscopy, it is likely that fixation cross-links intact surface-coat components associated with the ConA binding sites. It is evident from the studies in which lectins were employed that ligands containing alpha-D-mannose, N-acetylglucosamine, N-acetylgalactosamine, and alpha-L-fucose are randomly distributed in the outer surface of the pellicular and flagellar membranes of T. musculi trypomastigotes. Results obtained with alpha-amylase- and dextranase-treated trypanosomes suggested that lectin-binding sugar ligands in the cell surface were not directly associated with alpha-1,4 or repetitive alpha-1,6 glucan-bonded polysaccharide moieties. Similar conclusions can be drawn on the basis of neuraminidase treatment with regard to N-acetylated neuraminic acids. After thorough washing, intact, but not trypsin-treated trypomastigotes were agglutinated specifically with antisera against whole mouse serum and against mouse IgG. Evidently, adsorbed constituents of mouse serum are regular components of the T. musculi surface coat. After incubation in dilute whole mouse serum or in mouse IgG solutions, also the trypsinized cells were agglutinated by the 2 antisera. No such results were obtained with trypsinized cells incubated in serum-free buffers. It was concluded that mouse serum proteins were readily readsorbed on, and firmly bound to the trypsinized cells' surfaces. Specific agglutinations were obtained with trypsinized cells after incubation in dilute rat, rabbit, bovine, and human sera and in solutions of rat and rabbit IgG in reactions with the corresponding antisera. It seems, therefore, that the host serum proteins are adsorbed nonspecifically to the cell surface of trypsinized T. musculi bloodstream forms. When examined by electron microscopy, the intact trypomastigotes were covered by an ununiform, slightly granular, fibrillar extracellular coat, applied to the entire outer lamina of the pellicular and flagellar membranes. No indication of such a coat was noted in the trypsinized organisms. Flocculent surface coat-like matrix could, however, be discerned in cells which, after trypsinization, were incubated in various sera.
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PMID:The cell surface of Trypanosoma musculi bloodstream forms. II. Lectin and immunologic studies. 93 83

The alpha subunit of human chorionic gonadotrophin was reduced with dithiothreitol followed by carboxymethylation with iodoacetic acid. The modified glycoprotein was hydrolysed with trypsin to give various peptides, the identities of which were established, and glycopeptides. The glycopeptides were separated by gel filtration and ion-exchange chromatography; they were subjected to component analysis and were found to represent the two carbohydrate moieties in the parent glycoprotein. Sequential removal with glycoside hydrolases of monosaccharide units from the glycopeptides demonstrated (1) that galactose, mannose, glucosamine (2-amino-2-deoxyglucose) and neuraminic acid (5-amino-3,5-dideoxy-glycero-galacto-2-nonulosonic acid) residues possess the D configurations, (2) that the glucosamine units are N-acetylated and (3) the order of the monosaccharide units in the chain, the neuraminic acid units being furthest from the peptide backbone of the subunit and substituting the D-galactose units. Methylation analysis of the glycopeptides by adaptation of the Hakomori technique demonstrated that: (4) D-galactose, D-mannose and N-acetylglucosamine (2-acetamido-2-deoxy-D-glucose) units exist in the pyranose forms; (5) the D-galactopyranose units are linked in the 1 and 6 positions; (6) the D-mannopyranose units exist in several forms, one in a terminal non-reducing position, one as 1,2-linked residues and some as 1,6-linked branch points; (7) the N-acetylglucosamine units are 1,6-linked. On the basis of the results of methylation and enzymic analysis, structures are proposed for the carbohydrate moieties and the assignments are compared with other data previously obtained by periodate-oxidation studies [Kennedy et al. (1974) Carbohydr. Res. 36, 369-377].
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PMID:The structures of the carbohydrate moieties of the alpha subunit of human chorionic gonadotrophin. 93 81

The cell surface of embryonic chick liver cells contains transferases for mannose, fucose, galactose, N-acetyl-glucosamine and N-acetyl-neuraminic acid. Liver cells obtained by trypsin-dissociation of the tissue use the corresponding exogenous sugar nucleotides as substrates. The activities of the enzymes tested do not depend neither no the dissociation procedure nor on de novo protein synthesis. They vary considerably during development of the embryos, reaching maximal values at the 8th+/-1 day and at the 12th+/-1 day. Glycoproteins are the final stable endogenous acceptors for all sugars. Mannose transfer proceeds via a two or multistep reaction sequence. In a first step labile lipophilic intermediates are formed. Mannose can be liberated by treating the intermediates with 0.1 N HCl at 100 degrees C. In a second reaction step mannose becomes attached to glycoproteins. From embryonic chick liver cells a glycopeptide fraction has been obtained by pronase digestion followed by several purification steps. The purified glycopeptides inhibit all transferase systems and act as exogenous acceptors for mannose transfered from exogenous GDP-mannose.
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PMID:Cell surface glycosyl transferase activities in liver cells of developing chicken embryos. 94 93

Of four glycoproteins isolated from guinea pig testes, two were aspermatogenic (types I and IV) and two (types II and III) were inactive. The glycoproteins were rich in carbohydrate, varying from 41.5% to 49.5% carbohydrate by weight. Each glycoprotein had a unique amino acid composition, but in general low levels of tyrosine, tryptophan, and basic amino acids were found along with relatively high contents of serine, threonine, glutamic acid, and proline. Types I and IV glycoproteins were remarkably stable; their aspermatogenic activity was not affected by urea, trypsin, or heating at 100 degrees C in water or in 1 M HCl for 15 min. Carbohydrate analysis revealed little difference in the monosaccharide compositions of types I and IV glycoproteins, except that only the type I contained sialic acid. In contrast, types II and III glycoproteins lacked sialicacid and fucose and contained much less mannose. Both N-acetylglucosamine and N-acetylgalactosamine were present in all four glycoproteins, and they dominated in the types II and III. Fucose and at least 20-25% of the galactose appeared to occupy terminal positions in type IV glycoprotein as shown by their release after 15 min hydrolysis in 1 M HCl. All of the glycoproteins contained a relatively high percentage of galactose by weight, from 12.6 to 19.3%. The molecular weights of the glycoproteins were estimated by sodium dodecyl sulfate gel electrophoresis to be 47000, 105000 and 18000 respectively for the types I, II, and IV; type III glycoprotein showed two major bands, with molecular weights of 41500 and 22800. All the above molecular weight values are probably overestimated because of high carbohydrate content. The molecular weight of type IV glycoprotein was found to be 13000 by ultracentrifugation; a corrected value of 29000 was calculated for type I glycoprotein.
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PMID:Experimental allergic aspermatogenic orchitis. IV. Chemical properties of sperm glycoproteins isolated from guinea pig testes. 95 93


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